View Full Version : ESE's works engine tuner
TZ350
14th March 2009, 06:38
Great pictures of your new barrel Speedpro.
This is my new copper fin/head. The copper is 2mm thick. It has an aluminium combustion chamber like you suggested. There is an "O" ring grove in both the barrel and head to act as head gasket seals. This is probably the most practical version of the copper fin idea.
The effective copper fin area is 50% of the original alloy head fin area, a significant increase in engine cooling capacity. As copper has twice the thermal conductivity of aluminium, does this mean I have doubled the cooling capacity of the head?
My new head has the copper forming the squish area, In picture-1 I tried to mark it out with the black high-lighter so you can see where it is.
Picture-4, Thomas has made another copper head fin for one of the other bikes that has a conventionly domed piston and he was able to form the copper so it became a domed squish band. Seems to work OK.
I haven’t given up on the full copper head but solving the discoloration problem will have to wait. Racing is tomorrow and the bike is still all in bits. I will have to pull finger to get it ready. Another last minute rush :argh: again.
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Buckets4Me
14th March 2009, 11:50
hows that going to fit in my rs framed bucket ??????
come now think smarter :shutup:
see ya there sunday
TZ350
14th March 2009, 18:28
First points race of the year tomorrow. It's been pointed out to me HP won't win races and that I will go faster if I applied myself to learning to ride. Well they are right about that.
They say you go faster through a corner the further you look up the road. So instead off running around looking just ahead of my front wheel I will lift my head to look up the road as far as I can. lets see how that goes tomorrow.
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Bren_chch
14th March 2009, 19:14
First points race of the year tomorrow. It's been pointed out to me HP won't win races
.
they just scared! :lol:
TZ350
14th March 2009, 20:06
As a side note to all. It's not just about power, though it can mean lots. Don't underestimate handling. After changes to my handling I estimate I could take a second a lap off my Taupo times. Might get a cance to prove that at some stage.
That is truly frightening to hear. Hope to see you at Taupo again next year.
.
TZ350
14th March 2009, 20:17
I am thinking (after re-reading his earlier posts, in particular a race report) there is a big low R.P.M torque deficit (I make this statement after reading how he has to slip the clutch "all the way round the track").
Slightly over geared but more importantly was (dropping) not carrying enough corner speed. I know, :pinch: corner speed is everything with a bucket!
.
TZ350
16th March 2009, 16:34
Temperature Measurements. The measurements aren't that accurate, by the time I got back in took my helmet and gloves off the temperatures would be different to the actual running temps. But they give some idea of whats going on.
GP125 with Copper Head/Fin
Head....................94 Degrees C.
Copper/Fin............85
Lowest Barrel/Fin..127
Lower copper fins.117, 108, 98
Crank-Case...........80
G/Box Oil..............68
GP125 in the same state of tune.
Head...................127 Degrees C.
Lowest Barrel/Fin...101
Crank-Case...........98
FXR 4-Stroke
Head...................139 Degrees C.
Lowest Barrel/Fin...129
Crank-Case............71
The motor felt and sounded very sharp all day, never faded and left the line like a rocket. I am looking forward to the next meeting and some lightning fast starts.
My copper head/fin looks pretty hot in the exhaust port area but the combustion chamber looks ok. The piston is running about as hot as it can go. The real test is to look underneath to check the colour of the piston crown underside.
I am absolutely flabbergasted at the temperature of the Lower barrel fin but it looks like the copper head/fin is doing some good. When you look at the barrel temperatures and think that the fresh mixture is sitting in there its easy to see my next problem is to reduce the temperature of the lower barrel fins and thereby reduce the ingoing temperature of the fresh mixture.
When you look at a water cooled cylinders you see that the incoming water generaly enters the cylinder under the exhaust port cooling it first.
Having looked at all those aeroplane cowels I now have some ideas for ducting.
I think that if I can reduce the heat uptake of the exhaust into the cylinder and get the lower cylinder fin to run at less than 100 then the head will run less than 80 and that would be very good as I will be able to tune it closer to the power output of a water cooled motor.
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TZ350
16th March 2009, 19:25
First points race of the year tomorrow. It's been pointed out to me HP won't win races and that I will go faster if I applied myself to learning to ride. Well they are right about that.
They say you go faster through a corner the further you look up the road. So instead off running around looking just ahead of my front wheel I will lift my head to look up the road as far as I can. lets see how that goes tomorrow.
.
Well, looking up the road was easier than I thought but leaving the turn in point and apex in my peripheral vision will take some getting used too. I was either turning in to late or to early and running up the ripple strip. Trying to learn something new slowed me down a bit but I will get a handle on it.
Tried getting the power on earlier and had a mighty front end judder/slide, this happened two or three times more so there is a handling problem/ riding position to sort too. But looking up the road was more comfortable than I thought possible it will just take some getting used too.
.
Skunk
16th March 2009, 20:41
I find looking up the road helpful to go faster, but as you say, I can't help but look down at what I'm riding on. Either that or I miss the corner apex...
If you sort out a way the fix that, please, let me know. There's a couple of buggers down here I need to beat this year.
F5 Dave
17th March 2009, 10:17
You are a greyhound following a mechanised rabbit that streaks around the corner, visualise that & let your eyes follow it. Especially hard corner at Mt wgtn is the infield left hander. Some while back I sat at the apex & practiced looking around for a few min so I didn’t get lost while riding it.
You are a greyhound following a mechanised rabbit that streaks around the corner, visualise that & let your eyes follow it. . . . Sits in dark room . . You are Lightening, You are Speed (Cars movie)
TZ350
17th March 2009, 10:24
Thanks F5, Skunk and I are working on getting our heads around corners.
I am like, Holy Shit another corner!!! :shit: Fawwwk where is the brakes?????? to fast to fast, can't look. :pinch:
I will visualise the rabbit.
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speedpro
17th March 2009, 18:49
I got some good advice years ago - "slow down". I ended up 2 sec a lap faster at Puke. I still find it useful at new tracks or even at the start of practice to just go slow, get comfy, have a look around, and definitely don't try anything fast for quite a while. Some cruel people have suggested that is the way i ride all the time.
TZ350
17th March 2009, 19:17
I got some good advice years ago - "slow down". I ended up 2 sec a lap faster at Puke. I still find it useful at new tracks or even at the start of practice to just go slow, get comfy, have a look around, and definitely don't try anything fast for quite a while. Some cruel people have suggested that is the way i ride all the time.
Thanks Speedpro, good advice, I did give myself a bit of a head talk, slowed down and relaxed into trying the new riding style. Lots of people passed me easily but when on occasions I was able to keep my corner speed up instead of clutching it, the bike fair flew out of the corners on the throttle. I figured there are a lot of people in trouble (myself included) if I ever get the hang of this.
I know you can hire a key for the track. I would like to get down there during the week and just pootle around getting comfortable with the new riding style.
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TZ350
17th March 2009, 19:24
Aerodynamics.
I am looking at ducting air to the cylinder and head and generaly improving the aerodynamics.
Screen Scrape from Team Mad Dog Racing:-
If you decide to build a fairing from scratch, Cooper gave me the following hints: try to approximate a teardrop shape with a length to width ratio of 3 to 1. Have the widest point a third of the way back. Have a taper from front to back of 10 deg. preferred, and no more than 15 deg., as premature flow separation will occur and up the Cd. significantly. Keep the rider's body fully enclosed, with his back at the same 10 deg. angle. Pay special attention to the rear of the fairing, especially behind the rider as it is the rear of the bike where the greatest aerodynamic gains are to be made -- not at the front! When asked about the idea of the rear-mounted radiator, as used on the Britten and now on the James Parker-designed TZ-250 (Parker of RADD suspension fame), Cooper commented that it seemed logical, as the car guys have been doing it for years. He noted, however, that the ducting design is critical, and if done wrong can result in greater losses than a conventional design with regards to drag and cooling efficiency.
Regarding flow separation, it can be easily identified by taping tufts of yarn several inches long over the surface of the rider and body work. With a video camera and a chase car or bike, you can film the position of the tufts and identify where flow separation occurs. If the tufts are oscillating wildly, they are in turbulent air. If they are pulled back straight and tight against the body work, they are in laminat flow. This approach has been used by the aircraft and motor vehicle industries for years.
More of it can be read here:- http://race.commline.com/articles/TeamMadDog.html
I am going to try some of those aero ideas about ducting cooling air to the motor and will use the tufts of wool idea and a video camera to see how the air flow is moving.
Interesting about the riders back needing to be at 10 degrees.
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Skunk
17th March 2009, 21:33
I got some good advice years ago - "slow down". I ended up 2 sec a lap faster at Puke. I still find it useful at new tracks or even at the start of practice to just go slow, get comfy, have a look around, and definitely don't try anything fast for quite a while. Some cruel people have suggested that is the way i ride all the time.
Pickle told me the same thing. Did you two hear it at the same time or did you tell him? Can't imagine him telling you to slow down! :laugh:
Buckets4Me
18th March 2009, 12:56
You are a greyhound following a mechanised rabbit that streaks around the corner, visualise that & let your eyes follow it.
Sits in dark room . . You are Lightening, You are Speed (Cars movie)
I am the minivan with the bed on the roof :scooter:
TZ350
18th March 2009, 15:22
.
Gordon Jennings on top end rebuilds, porting and piston clearance
“With pistons fitted to close .00016 to .00018 inch clearance will run faster and more reliably than one that’s a little loose. You are entitled to wonder why a tightly fitted piston should give a horsepower edge and have a lessened tendency to seize?”
http://www.bridgestonemotorcycle.com/documents/topend_rebuild6.pdf
and how you can sharpen your bike’s performance with a $20 investment in rifflers and rasps.
“Until you’ve tried it, do-it-yourself porting looks like the kind of work that should be easy, inexpensive, and a sure-fire way to coax more horsepower out of the motorcycles engine.” But…….
Down load the complete article here.
http://www.bridgestonemotorcycle.com/documents/topend_rebuild6.pdf
The complete 2stroketunershandbook can be down-loaded here:-
http://www.bridgestonemotorcycle.com/documents/2stroketunershandbook.pdf
Gordon Jennings 2-stroke time area’s for porting can be found here:-
http://www.bridgestonemotorcycle.com/documents/aspirin_takers6.pdf
Do you really want to know about expansion chambers? Gordon Jennings
http://www.bridgestonemotorcycle.com/documents/do_you_really6.pdf
A lot of other good stuff can be found here:- :eek:
http://www.bridgestonemotorcycle.com/documents/
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TZ350
18th March 2009, 16:07
Port map calculator. I have an earlier version, it works great, costs $16.25 USD and you can pay by Paypal.
Take a look:- http://www.porting-programs.com/
Calculates port heights port durations and shape based on port time areas as defined by Jennings and Blair for a desired rpm operating range.
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TZ350
18th March 2009, 20:24
From:- http://drunkmunkey6969.googlepages.com/malossi210vspolini210
Transfer ports....its something we come back to again and again on Vespa and Lambretta scooters. In comparison to modern design, the transfer ports are the biggest let-down of scooter engine design. By enlarging the surface area of the transfer ports (see porting work on side and boost transfers above) and also cutting away a portion of the cylinder wall.....we can vastly increase the performance of the kit.
A cagiva 125 cylinder next to a Malossi cylinder, merely to illustrate how modern 2-stroke design incorporates massive ports and transfers as part of their standard production performance. Those sider transfers must be at least 4 times as large as the Malossi!
If top Scooter performance is your goal....then the cases must be ported. Its just common sense. A past article in Scootering magazine demonstrated (using a dyno reading) that merely bolting on a Malossi 210 cylinder, with no other alterations (other than jetting and timing) only gave a 2bhp improvement....but with additional porting and an expansion chamber, it gave approx 9bhp extra than standard!
Also, as mentioned earlier, the cylinder and casings can be ali-welded to build up new surface area, and then carve out massive race-style transfer ports, this is quite a time consuming task, but the results are fantastic.
The five'th pic is of the case transfers of a Honda RS125.
I can now see why SS90 was so keen on "unmasking the transfers" but it looks like Bike development is allready way ahead of Scotters.
Last Pic. Top Left: Standard Mallossi 210, Top Right: MB Developments 225 TS1 - stage 2 road/race, Bottom Left: Cagiva 125 cylinder for comparison, Bottom Right: Sean Brady 'wild race' 225 TS1 - work in progress.
The pictures say it all really. :yes:
.
Bren_chch
18th March 2009, 20:29
thanks for all the pdf files, good reading.
TZ350
18th March 2009, 21:22
From:- http://drunkmunkey6969.googlepages.com/wildlambrettaraceporting-workinprogress
Check this out, Sean has been working on this totally 'balls out' race porting for one of his Lambos....
The pictures below show what is basically a 'work in progress' but you get the idea of what is going on!
If you compare the transfers of a standard Cagiva 125 cylinder, to the race porting Sean is working on....you'll see where the idea comes from!......................................
In a reply to SS90 F5Dave said:-
Since the dawn of time people have been adding more transfer ports, often fed by the piston with holes near the top. This does smack of a compromised transfer arrangement. To put them in the main transfers more so.
I suspect this is borne of your typical scooter having a very compromised crankcase design affecting where you can place & feed transfers......................................... ....
I can now see what he meant. Looks like the Scooter boys get their best insperation from current Bike technology.
I had hoped SS90 was onto something new with his talk of unmasking the transfer ports but it does not look like it. Still those big bore, stripped down racing scotters with 30HP go fast and look mean.
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speedpro
18th March 2009, 21:40
That huge intake port would cause me to be concerned about piston support. Skirts could end up cracking which is why my intakes are like they are - area with support.
bucketracer
18th March 2009, 21:42
Looks like SS90 the super scotter tuner :yawn: is mistaken about how much he knows and had to offer.
TZ350
18th March 2009, 22:13
That huge intake port would cause me to be concerned about piston support. Skirts could end up cracking which is why my intakes are like they are - area with support.
Below they talk about the overly wide inlet and how improving the transfers allows a smaller inlet/exhaust port and also how Japanese bikes are on the money.
From:- http://drunkmunkey6969.googlepages.com/ts1cylinderporting
Pic 1. Inlet port on the all out race cylinder is colossal in comparison to the stage 2 cylinder on the left. This will lead to awesome all out performance....but due to the decreased life of the piston and rings, its not the kind of thing you'd do 12,000 miles worth of touring on!
Pic 2. On the left, these transfers really help to increase the power dramatically, but without the wear problems associated with oversized inlet and exhaust ports. Which is why so many jap bikes have fantastic transfer port set ups these days.
Guess what I race??? I recon I am on the right track.
.
SS90
19th March 2009, 04:03
Looks like SS90 the super scotter tuner :yawn: is mistaken about how much he knows and had to offer.
Oh dear, it just keeps getting better...
For your information.... the pictures of the Vespa engines (and transfers) are from a "big Frame" Vespa, and totally different to a "small frame Vespa"
The design of which is not too dissimilar to a modern single cylinder Japanese engine (well, in terms of layout anyway)
The picture I have attached is of the transfer areas of ONE of my over 25 Hp Engines..... I make these for a living.
SS90
19th March 2009, 04:42
Have some more pictures (no, I won't show you what the port layout is)....
Oh, in the workshop, we have a new "Joke"........
"Der Kurbelwelle Gehäuse ist nur inen platz fur benzine und luft gemish laden........"
(In English)........
"The crankcase is just a place to store the fuel......"
No, it is not.
I really know what I am talking about here guys.
TZ350
19th March 2009, 05:41
SS90, Good to see some pics. Interesting to see what others are up to. I like the look of the cut down mean as Scotter Racers I see at Mt Wellington, just like the bare frame look of the Atom Car.
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Buckets4Me
19th March 2009, 05:55
Oh, in the workshop, we have a new "Joke"........
"Der Kurbelwelle Gehäuse ist nur inen platz fur benzine und luft gemish laden........"
(In English)........
"The crankcase is just a place to store the fuel......"
No, it is not.
I really know what I am talking about here guys.
no the fuel tank is
the crankcase is where you store the fuel air mix :yes:
:scooter:
SS90
19th March 2009, 06:24
Running the risk of repeating myself, but.
The crankcase IS NOT JUST A PLACE TO STORE THE AIR FUEL MIXTURE.
Anyone who thinks that's what it's primary role is, (to store the air/fuel mixture) then they would be better off racing model trains.
One important fact I have clearly pointed out previously is that the crankcase is actually part of the intake maninfold.....
This is a BASIC fact that anyone who wants to tune a two stroke engine must know.
I used this example (which was posted by Prospeed) because it is clearly an incorrect statement, and I use it not to ridicule him, but it's just an example of how alot of things are being missed (the basics), in the quest for more power, at the expense of temperature.
I tried to point out about pumping efficiency (and how the mods to teezee's engine had lowered this to less than the industry established 1.5:1, therefore DECREASING it pumping efficiency more.
This is in addition to the 24mm carb (as per the rules) causing even more pumping losses.
Does anyone know what a "scavenge pattern " is?
If anyone does, please post a) what a "scavenge pattern" is, and b) how they effect your engine.............
I tried to point this out, even by giving details of a "closed loop" system......which almost every two stroke is....... but no-one seemed to care.
Chambers
19th March 2009, 06:52
The picture I have attached is of the transfer areas of ONE of my over 25 Hp Engines..... I make these for a living.
Hi SS90, so we can compaire apples with apples would you please tell us how many CC's your 25HP motor is.
We run a very usable air cooled 100 which we are confident is making 18Hp, others are getting 23+ but much more peeky.
Our 18hp 100 equates to 180 bhp per Liter whats yours?
.
bucketracer
19th March 2009, 06:58
I really know what I am talking about here guys.
Yesssssss so you keep telling us, we are bored with it.
How about something that shows us you understand what you have read!
bucketracer
19th March 2009, 07:01
Oh, in the workshop, we have a new "Joke"........
"Der Kurbelwelle Gehäuse ist nur inen platz fur benzine und luft gemish laden........"
(In English)........
"The crankcase is just a place to store the fuel......"
Oh, in the workshop, we have a new German Joke. about :spanking: the monkey.
SS90
19th March 2009, 08:16
Hi SS90, so we can compaire apples with apples would you please tell us how many CC's your 25HP motor is.
We run a very usable air cooled 100 which we are confident is making 18Hp, others are getting 23+ but much more peeky.
Our 18hp 100 equates to 180 bhp per Liter whats yours?
.
Sure.
the 25hp motor is 125cc
the 28hp 140cc
There are several other cylinders available on the market to suit the same engine, and the best is 30hp, (and that's the 125cc one!) "Plug and play" (which admittedly is a nicasil coated cylinder, and VERY well designed)
Check out this.....
http://www.falcracing.it/cilindrivespa.html
This guy developed a cylinder, that has now turned into a series (long strokes, short strokes, different bore size).
Also builds VERY fast RS125's as well.
Are people getting 23+ P.S with a 24mm carb?
Do you have some dyno runs you can post?
It's a valid point about rideability..... I'm not really a "scooterist", I just like the opportunity it provides, but the best "tuned scooter" I have ridden was only 23 P.S and 20 NM. But the damn thing made peak power for about 3500 RPM.
There is plenty of scope for getting more power (especially with the Nicasil cylinders), but you are hampered by the fact you only have 4 gears, and there is a big "jump" in the ratio from 3rd to 4th.
The thing you ask anyone who has a high H.P engine, is "does it pull 4th?"
You can change primary drives, but it makes them too "revvy" for day to day use.
I spent alot of time with port design (and too many exhausts to count) to get a good balance of power and torque (in the low R.P.M), as early results where very good (as far as peak power went), but it was too "Peaky" to be nice to ride.
Buckets4Me
19th March 2009, 09:24
Oh, in the workshop, we have a new German Joke. about :spanking: the monkey.
Thats animal abuse I'm telling the R.S.P.C.A :pinch:
The crankcase is also where you store all the broken bits from the engine as well as the air fuel mix :Oops: forgot that part
did you see the pics I put up of the bike in action ???
tell ned kelly he needs more knee sliders
123200
123201
123202
123203
F5 Dave
19th March 2009, 10:37
. . .
Does anyone know what a "scavenge pattern " is?
If anyone does, please post a) what a "scavenge pattern" is, and b) how they effect your engine.............
I tried to point this out, even by giving details of a "closed loop" system......which almost every two stroke is....... but no-one seemed to care.
The basic idea I'm sure everyone is aware of, it is in every 2 stroke book, probably even Roy Bacon's old duffer books. To get a visualization run some water through the bottom of the transfers & see where the flow is directed, - this of course is not a full dynamic model but is interesting & with later designs how this has evolved & how effective the kicks have become esp in the 2ndries. Where this flow ends up & how effective it is in containing charge by reducing kinetic energy & purifying what is left will all affect the result. Overboring or sleeving will put this to pot a bit wrt to transfers.
Buckets4Me
19th March 2009, 11:21
The basic idea I'm sure everyone is aware of, it is in every 2 stroke book,.
no it's not you dope
it goes like this
tz can I have your old frame
how about your old engine
can I have those slicks
I need some rims to fit the slicks 2
you dont realy need that seat do you
can i borrow some gas (and oil)
I need a new spark plug you got any spare ????
Keep your hands off Scott they are mine :bleh:
now thats how a bucket racer scavanges :msn-wink: some of us even look in the crankcase for lost bits and pieces
I found some roller bearings between the crank bearing and oil seal on the rg50 the other day (a spare engine not my good one) havent found a use for them YET!!!
now where can I find a decent pipe from
bucketracer
19th March 2009, 11:57
Originally Posted by SS90
. . .
Does anyone know what a "scavenge pattern " is?
If anyone does, please post a) what a "scavenge pattern" is, and b) how they effect your engine.............
I tried to point this out, even by giving details of a "closed loop" system......which almost every two stroke is.......
but no-one seemed to care.
Not true! SS90, TZ350 answered that a while ago and even gave them their correct name.
Quote:- from TZ350
"Jante Patterns do you know what they are SS90 if not, you can find examples of them on P182 The High-Performance Two-Stroke Engine. Dr John C. Dixon."
TZ350 also recently posted a link to a site that discribed all the various two stroke designs.
SS90 your not keeping up! do make an effort to stay with the programe.
F5 Dave
19th March 2009, 12:58
no it's not you dope
it goes like this
tz can I have your old frame
how about your old engine
can I have those slicks
I need some rims to fit the slicks 2
you dont realy need that seat do you
can i borrow some gas (and oil)
I need a new spark plug you got any spare ????
Keep your hands off Scott they are mine :bleh:
now thats how a bucket racer scavanges :msn-wink: some of us even look in the crankcase for lost bits and pieces
I found some roller bearings between the crank bearing and oil seal on the rg50 the other day (a spare engine not my good one) havent found a use for them YET!!!
now where can I find a decent pipe from
. . . yes I think TZ had been preconditioned for a few years as well, something along the lines of "Can I have some more pocket money I've run out" "Can I borrow the car" and so on.
Yow Ling
19th March 2009, 13:59
now where can I find a decent pipe from
Cosmic Corner maybe
Good example here of looking outside the square re scavenging, trade me is another good but more expensive scavenging technique
TZ350
19th March 2009, 15:15
. . . yes I think TZ had been preconditioned for a few years as well, something along the lines of "Can I have some more pocket money I've run out" "Can I borrow the car" and so on.
You got kids too then F5?
Kids, they are great scavengers, mine send me loopy. :crazy: and they know a thing or two about transfering wealth from my pocket.
.
TZ350
19th March 2009, 15:31
I have been thinking alot recently about how to keep heat from entering the GP125's cooling system and the exhaust tract was the most obvious problem area.
I couldnt help thinking there looks like insuficent cooling fin area on the scooter cylinders for sheding the wast heat from 25+hp even with forced air cooling from a fan. But looking at the scooter cylinder pictures I realised they have a much shorter exhaust port tract than the GP.
I would expect a shorter port to take up a lot less heat into the cylinder giving the cooling system a much easier time of it.
Now that I have seen this I remember my 1970 Suzuki TR250 had the exhaust port flanges milled right back into the cylinder shorting the exhaust tract considerably. I wonder if reducing the heat uptake through the exhaust port tract was the reason for doing it, those crafty old Suzuki tuners.
looking at the right hand cylinder in the middle picture you can see how short the exhaust tract is, and also the very clean (unmasked, is that the right term?) looking entries to the transfers.
.
F5 Dave
19th March 2009, 16:01
You got kids too then F5?
Kids, they are great scavengers, mine send me loopy. :crazy: and they know a thing or two about transfering wealth from my pocket.
.
None outside the womb, but I have a reasonable memory from being a kid. My Dad didn't pass me on any race bike parts sadly, even if he was a dab hand with the right angle grinder. . . Mostly in Enamel though;).
F5 Dave
19th March 2009, 16:05
Before you get carried away with transfer bottoms & all that palaver do drop a piston into the bore & ideally a case 1/2 with crank. No point looking at them in isolation, bit like porting 4 strokes without the valve etc.
TZ350
19th March 2009, 16:36
Before you get carried away with transfer bottoms & all that palaver do drop a piston into the bore & ideally a case 1/2 with crank. No point looking at them in isolation, bit like porting 4 strokes without the valve etc.
Good point, thanks. the transfer bottoms & all that palaver is something I am keen to get into but it will have to wait untill the motor comes apart again for maintenance.
.
SS90
19th March 2009, 20:07
F5 Is quite right about putting the piston in the cylinder, then onto the case half.
There are phenonenal amounts of power to be made by using the right shapes.
This is also true of the scavenge patterns.
f5 also points out about the kickers (obviously you cannot incorporate kickers into your cylinder with out removing the liner, which is a shame)
But it goes to show that if you paid alot of attention to this area, huge gains can be made, and as you have such a small carb, it is even more important to get more efficiency.
Modern scavenge patterns improve efficiency dramatically. I, at first doubted such gains, but was proven wrong when I saw the gains it made on other engines, so I made the effort to change the patterns I was using.
The gains where amazing for such a small change.
In regards to heat Teezee, expansion chamber development over the last few years has enabled these engines to be making in excess of 30 P.S, and have no problems.
Of course, at that level of power, set up has now become critical, and of the Falc cylinders I have seen fail, all have seen severe errosion of the exhaust side piston crown, which suggests too much ignition retard.
TZ350
19th March 2009, 20:41
In regards to heat Teezee, expansion chamber development over the last few years has enabled these engines to be making in excess of 30 P.S, and have no problems.
I understand from the efficency of the Carnot Cycle that it does not matter what chamber, transfer layout or any other arrangement you have, when you make 30 P.S.....
Carnot Cycle:- http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/carnot.html
Using the simpler 1/3 rule of thumb, 1/3 for work, 1/3 down the exhaust and 1/3 waste heat.
30 P.S, means about 22,500 Watts of waste heat that the cooling system has to deal with.
The scooters don't look like they have all that much finning, do you use a special fan for the cooling?
.
speedpro
19th March 2009, 20:45
. . . of the Falc cylinders I have seen fail, all have seen severe errosion of the exhaust side piston crown, which suggests too much ignition retard.
Every time I have seen piston crown erosion on the exhaust port side subsequent dyno runs have proven the timing to be a smidge advanced. With a few other tuning stuff ups I've managed to get piston crown erosion right in the middle. Not turning the water pump on was good for doing that as well.
Attached is a pretty old dyno chart. Ignore the red line that was a dodgy experiment. The line going to 13,500 was the old MB100 sidecar. That engine only had the original 2-petal reed block and a 28mm Keihin. The other line is my old piston port only TS100. 200deg timing on both intake and exhaust. I have no idea why it made such good power. Both peaked at 19.9rwhp.
As an experiment last Saturday at the track I held the throttle so that the carb was only part open, effectively creating about a 24mm venturi. The motor melted due to pumping losses, or something.
Fooman
19th March 2009, 20:55
30 P.S, means 22,500 Watts of waste heat ( using the 1/3 rule of thumb).
Do you use a special fan for cooling?
.
Remember, not all the waste heat from the combustion is going into the cylinder head/barrel - quite a large amount goes out the exhaust, mainly in (superheated/saturated) H20 (lot of energy "stored" in steam). As you pointed out in your edit.
There I will stop, as I know sweet FA about dirty, disgusting 2-strokes - must learn more, having just inherited a GP100 with a watercooled head...
But, with respect to your oxidation problem with the copper lining, if you want to get a decent amount of copper in the chamber, try a thin coat of nickel (by thin, maybe 50 to 100 µm) or a nickel aluminide. The latter may be, um, difficult, to obtain over the counter as it were. That should be reasonably oxidation resistant. If it is thin, it won't affect heat transfer that much
Cheers,
FM
Ohhh, you edited it while I replied.
Buckets4Me
19th March 2009, 21:06
The motor melted due to pumping losses, or something.
bet you filled the crankcase up with petrol as well :Pokey:
wondered why you wernt there sunday
Nigel was fair flying
from back of the grid to 3rd before the first corner
then slowly picked Rick then Tim of to win every race
Zak made a desperat bit to pass Dave D on the last corner of the last race and hit him binning the Fxr Finished the race by pushing it over the line :buggerd:
TZ350
19th March 2009, 21:14
Remember, not all the waste heat from the combustion is going into the cylinder head/barrel - quite a large amount goes out the exhaust, mainly in (superheated/saturated) H20 (lot of energy "stored" in steam). As you pointed out in your edit.
There I will stop, as I know sweet FA about dirty, disgusting 2-strokes - must learn more, having just inherited a GP100 with a watercooled head...
The 1/3 rule of thumb says that if you are making 30PS (about 22,500 Watts) then you have:-
22,500 Watts of power 22,500 Watts of exhaust heat and 22,500 Watts of waste heat in the cooling system.
Only about 1/3 of the energy of combustion does any usefull work.
Ohhh, you edited it while I replied.
Sorry. :no:
.
speedpro
19th March 2009, 21:25
pg31 of the tuners pdf has interesting comments about the effects from the chamber on the transfer of mixture up the transfer ports and attributes the swift action equally to crankcase compression(7psi) and chamber created partial vacuum(-7psi). A crankcase compression ratio of 1.5:1 gives 7psi and also yields a volume that will be 1.5 times the cylinder swept volume. That volume may be a handy amount to have generally. If you were to remove a swept volume(only) of mixture from the cases the pressure would be back to atmospheric with the piston at BDC. With a larger volume you could extract the swept volume and still have a partially pressurised crankcase which wasn't resisting the continued flow of mixture up the transfers. Transfer flow would lose a bit at "first" due to lower crankcase pressure but would be compensated by what pressure there was dropping at a lower rate. You also have to consider when you think most of the transfer takes place and what is contributing to that flow at that time.
If the chamber is particularly effective it may be able to extract more mixture than is available. Reed valves are good here as they will admit more mixture to the cases if required. A late closing disc valve will do the same if the resonance is right. Of course it lets mixture escape back out the carb when it isn't. This is where my assertion that the crankcase is a storage container for the mixture comes from. I don't fully understand exactly what happens but from discussions it seems to be better to have the mixture required already in the cases. Something to do with inertia though I'd think that could be used to advantage if your lengths and volumes were right. Reed valve inertia plays a part as well and I think they will be closed and stay closed at about this time. Wobbly was adamant that my motor needed more crankcase volume to get the power I wanted(the most) at the revs the engine is now capable of. He's made a pretty good living doing this design work so I wasn't going to argue.
TZ350
19th March 2009, 21:33
Good post Speedpro.
Gordon Jennings book.
http://www.vintagesleds.com/library/...20Handbook.pdf
Page 106 talks about crankcase pumping.
.
TZ350
20th March 2009, 04:31
“Experience is what you get when you don't get what you want.”
Thomas recomends these books on Two Stroke Tuning.
(Some of these are PDF's that can be down loaded, read them then get a copy of the book)
Graham Bell
http://www.kreidler.nl/artikelen/performance-tuning-graham-bell/performance-tuning-graham-bell.pdf
Gordon Jennings
http://www.vintagesleds.com/library/manuals/misc/Two-stroke%20Tuner's%20Handbook.pdf
http://toostroke.blogspot.com/2007/12/two-stroke-tuners-handbook.html
Engine Formulas
http://members.bellatlantic.net/~vze2p5sj/modelengines/engine1.htm
Reading Plugs.
http://www.dragstuff.com/techarticles/reading-spark-plugs.html
Rate of fuel burn and how it affects power output
http://www.factorypro.com/tech_tuning_procedures/tuning_fuel_octane_vs_power.html
.
SS90
20th March 2009, 05:28
pg31 of the tuners pdf has interesting comments about the effects from the chamber on the transfer of mixture up the transfer ports and attributes the swift action equally to crankcase compression(7psi) and chamber created partial vacuum(-7psi). A crankcase compression ratio of 1.5:1 gives 7psi and also yields a volume that will be 1.5 times the cylinder swept volume. That volume may be a handy amount to have generally. If you were to remove a swept volume(only) of mixture from the cases the pressure would be back to atmospheric with the piston at BDC. With a larger volume you could extract the swept volume and still have a partially pressurised crankcase which wasn't resisting the continued flow of mixture up the transfers. Transfer flow would lose a bit at "first" due to lower crankcase pressure but would be compensated by what pressure there was dropping at a lower rate. You also have to consider when you think most of the transfer takes place and what is contributing to that flow at that time.
If the chamber is particularly effective it may be able to extract more mixture than is available. Reed valves are good here as they will admit more mixture to the cases if required. A late closing disc valve will do the same if the resonance is right. Of course it lets mixture escape back out the carb when it isn't. This is where my assertion that the crankcase is a storage container for the mixture comes from. I don't fully understand exactly what happens but from discussions it seems to be better to have the mixture required already in the cases. Something to do with inertia though I'd think that could be used to advantage if your lengths and volumes were right. Reed valve inertia plays a part as well and I think they will be closed and stay closed at about this time. Wobbly was adamant that my motor needed more crankcase volume to get the power I wanted(the most) at the revs the engine is now capable of. He's made a pretty good living doing this design work so I wasn't going to argue.
Nice to see you have been doing some reading.
As I pointed out in my earlier posts, particularly about "raising the primary compression", I was very cautious how I worded it, as, yes, normally, people cry "raise the primary compression", which indeed was true......50 years ago, as most two strokes where closer to 1.4 (or less), and therefore useless for anything like high speed operation.
Since the 70's, pretty much every two stroke engine comes standard with near enough to 1.5:1, and as such increasing it would only cause a peaky engine.
However..... Teezee, had lowered his (by modifications to make gains in other areas), and, as he measured it now to be something like 1.33:1, it's pretty clear it needs to be increased.
I did not advocate "just raise it".
And I quantified that with points I have just repeated here.
What is the ratio on your current engine?
I surmise while it may well be lower than 1.5:1 (but only just), and far more than TeeZees current 1.33:1
also remember, I have pointed out previously that the crankcase in a two stroke is also part of the intake manifold, and, as such, critical in tuning!
Every single engine is different, and while all the same rules apply, it's the application of those rules (depending on your criteria, like the fact that Teezee has to run a 24mm carb), that make tangible gains.
Current tuning "trends" are going towards lower ratios, yes, but those "lower" ratios are more like 1.48:1, I have seen nothing lower than 1.47:1
bucketracer
20th March 2009, 06:19
Does anyone know what a "scavenge pattern " is?
If anyone does, please post a) what a "scavenge pattern" is, and b) how they effect your engine.............
Home work from the Teacher, anyone done it yet? :nono:
Nice to see you have been doing some reading.
Once again Teacher, I dont know if you were borne stupid or if its a practised habit but your ability to offend is probably getting in the way of your message.
.
SS90
20th March 2009, 06:25
I understand from the efficency of the Carnot Cycle that it does not matter what chamber, transfer layout or any other arrangement you have, when you make 30 P.S.....
Carnot Cycle:- http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/carnot.html
Using the simpler 1/3 rule of thumb, 1/3 for work, 1/3 down the exhaust and 1/3 waste heat.
30 P.S, means about 22,500 Watts of waste heat that the cooling system has to deal with.
The scooters don't look like they have all that much finning, do you use a special fan for the cooling?
.
Ermmmm, I'm not quite sure of the relevence of the Carnot theorem here, (and how it relates to a Scnürle loop two stroke)
Especially when Carnot himself realised that in reality it is not possible to build a thermodynamically reversible engine.
Can you elaborate?
With the fan question, The shroud remains original, and is only cut to allow fitting over the large reed block housing (the reed block itself causes a cooling interference, but is of little consequence, especially if you drill a few holes on the back side to stop "hot air" being trapped at the small original outlet)
Don't forget that the 30 P.S plus engines are all Nicasil coated, not cast iron lined, as as such are around 30% better at dissipating heat than the lined ones.
The original fans supply plenty of air, and there are a few options for lighter fans (as the fans are part of the flywheel), which have less fan area, but cause no problems.
SS90
20th March 2009, 06:28
Home work from the Teacher, anyone done it yet? :nono:
Once again Teacher, I dont know if you were borne stupid or if its a practised habit but your ability to offend is probably getting in the way of your message.
.
Sorry, I can't resist......Can anyone spot the spelling mistake from this "pupil"........
"Borne stupid".....me??????? :2guns:
For the record, I have never claimed to be "teaching"...... I am constantly being asked to "prove things", and I try to do so in a simple easily read manner.... are you able to contribute anything to this thread other that antagonism.......
bucketracer
20th March 2009, 06:56
Sorry, I can't resist......Can anyone spot the spelling mistake from this "pupil"........
"Borne stupid".....me??????? :2guns:
:laugh:
For the record, I have never claimed to be "teaching"......
No, but you come across that way and it spoils what you have to say.
.
SS90
20th March 2009, 06:59
Every time I have seen piston crown erosion on the exhaust port side subsequent dyno runs have proven the timing to be a smidge advanced. With a few other tuning stuff ups I've managed to get piston crown erosion right in the middle. Not turning the water pump on was good for doing that as well.
Attached is a pretty old dyno chart. Ignore the red line that was a dodgy experiment. The line going to 13,500 was the old MB100 sidecar. That engine only had the original 2-petal reed block and a 28mm Keihin. The other line is my old piston port only TS100. 200deg timing on both intake and exhaust. I have no idea why it made such good power. Both peaked at 19.9rwhp.
As an experiment last Saturday at the track I held the throttle so that the carb was only part open, effectively creating about a 24mm venturi. The motor melted due to pumping losses, or something.
Ermmm, on the subject of exhaust side piston crown errosion, and too much retard.
As we all know, the primary reason for having a two stroke ignition that retards with R.P.M is to maximise for "peak pressure".
When you have very large exhaust ports, and then enlarge them more,(like all tuned cylinders are), you subject the exhaust side of the crown to increased heat.
If you have too much ignition advance, yes, you can erode the exhaust side away (particulary if you have a very wide exhaust port, by that I mean exhausts that use "bridges" allowing some phenominal exhaust port areas (exceeding 75% bore size).
On engines with-out exhaust bridges, as the port area is limited to somewhat less than 75%, the exhaust side of the piston crown is not subjected to so much "localised" heat, and normally, the hottest part seems to be the centre.
And normally, if you see a two stroke with a hole in the center of the piston, for whatever reason the overheating occured (be it jetting, or too much advance, or whatever), than engine is most likely not to have a bridged exhaust, and therefore smaller exhaust port size, and consequently less localised heating of the exhaust port side of the piston crown.
With alot of people experimenting with ignition timing, (especially on a dyno), it seems common pratice to advance their timing as much as possible, to get the best results.
Now, if you advance your timing "statically" (i.e-: move your stator plate), Since pretty much every "performance" two stroke, and most commuters (but not all), have a retard curve that functions solely on R.P.M, you also move the point that the ignition starts to "retard".
And therefore, the point where it "stops" retarding is further in the R.P.M range. And quite often, that new point can be too late.
Think of the factory setting of the advance curve only knows the original timing point as zero, if you move it ( for example, static timing minus 5 degrees), then the ignition retards that same amount later...... and finishes that same amount later.
Now that the timing is later than it's optimum, rather than firing causing nice combustion at "peak pressure" it causes a bigger "flame" to roar down the exhaust side of the crown, and into the exhaust port. (i.e AFTER the "peak pressure" moment has passed), when peak pressure is considered to be at 10deg? (I can't remember exactly!), think about how much of the exhaust port is exposed, if it happens later (15 deg, or what ever) much more of the exhaust port is exposed, exposing the exhaust side of the crown to greater localised heat.
Sure, too advanced timing can cause this type of erosion, but too retarded can cause the same effect.
This is one of the many reasons why fully adjustable ignition maps are so damn good!
You can set when and where (and how much) retard you have, rather than the basic R.P.M triggered system most every bike has. This basic system doesn't know how many R.P.M you have, it just knows 0.
SS90
20th March 2009, 07:00
:laugh:
No, but you come across that way and it spoils what you have to say.
.
Well, lets leave all that in the past and move on......... Please.......
bucketracer
20th March 2009, 07:07
. are you able to contribute anything to this thread other that antagonism.......
Check the Teachers grammer....... :bleh:
Yep I can....and I will also do you a favour and let you know when you are coming across as a dickhead......its what I am good at, after all we cant all be Teachers, if I antagonise you SS90 please understand its not my intention........
.
F5 Dave
20th March 2009, 09:17
. . . . Reed valves are good here as they will admit more mixture to the cases if required. . . .
Or directly into the combustion chamber via the boost port, clear section experimental engines with high speed cameras have shown the reed closing from intake & then upper fingers of reed opening again to feed the chamber purely through pipe vacuum.
. . .. . Something to do with inertia though I'd think that could be used to advantage if your lengths and volumes were right. Reed valve inertia plays a part as well and I think they will be closed and stay closed at about this time. Wobbly was adamant that my motor needed more crankcase volume to get the power I wanted(the most) at the revs the engine is now capable of. He's made a pretty good living doing this design work so I wasn't going to argue.
Reed petal inertia will affect how quickly the reed acts to close, but the inertia of the incoming gas will keep the reed open longer slightly over stuffing the crankcase.
That all being said in the existing classes that power is important (125 & 250 GP) Disc valve is king. Reeds are still a big obstruction to the inlet, but life is about compromise.
F5 Dave
20th March 2009, 11:58
Hey I just read that old G Jennings Cycle mag article on piston/bore relationship & learn-ed sumfing. You don't have to smoke 2Baccy to enjoy the flavour.
You can chew it.
There, no issues with lung cancer to worry about:rolleyes: (not that we believed that, - they said there was no scientific proof anyway:doctor:).
1975 was another time another place huh?
TZ350
20th March 2009, 15:42
Ermmmm, I'm not quite sure of the relevence of the Carnot theorem here, (and how it relates to a Scnürle loop two stroke)
Especially when Carnot himself realised that in reality it is not possible to build a thermodynamically reversible engine.
Can you elaborate?
Scraped and edited from Wikipedia
..............................................
For any engine there is a limiting obtainable efficiency it is called the Carnot cycle efficiency because it is the efficiency of an unattainable, ideal, heat engine cycle called the Carnot cycle. No heat engine, regardless of its construction, can exceed this efficiency.
In practice, because the operating cycles of real engines are nowhere near as efficient as the Carnot cycle, coupled with other irreversibilitys such as the combustion process itself and friction, real engines fall far short of the Carnot efficiency. Real automobile engines are only around 25% efficient.
Carnot Cycle:- http://en.wikipedia.org/wiki/Carnot_cycle
Thermal Efficiency:- http://en.wikipedia.org/wiki/Thermal_efficiency
Internal Combustion Engine:- http://en.wikipedia.org/wiki/Internal_combustion_engine
..............................................
Referenced it to support the 1/3, 1/3, 1/3 rule of thumb I used to gestimate the waste heat to the cooling system.
.
TZ350
20th March 2009, 16:10
With the fan question, The shroud remains original, and is only cut to allow fitting over the large reed block housing (the reed block itself causes a cooling interference, but is of little consequence, especially if you drill a few holes on the back side to stop "hot air" being trapped at the small original outlet)
The original fans supply plenty of air, and there are a few options for lighter fans (as the fans are part of the flywheel), which have less fan area, but cause no problems.
Waste heat to the cooling system is my current focus and I am interested in the practicalities of your cooling arrangements.
Do you think the shorter exhaust port tract on the Scooter reduces the heat takeup into the cooling system? The mean length of the GP125's exhaust tract is about 55mm long.
I would find it useful to know a Scooters head temperature and lower fin temperature measured near the exhaust after a good run, as a comparison. Would you measure it for me?
Because of your enthusiasm for crankcase compression ratios, induction resonance and unmasking the transfers I have become interested in looking at it again to see what more can be done with the GP.
But any practical work will have to wait for a little bit until I get to strip the motor for some gearbox maintenance that needs doing. Because of a damaged clutch nut thread I need to replace the main shaft.
.
TZ350
20th March 2009, 16:14
Don't forget that the 30 P.S plus engines are all Nicasil coated, not cast iron lined, as as such are around 30% better at dissipating heat than the lined ones.
Isn't Nicasil more heat transfer cooling for the piston than engine cooling as such?
.
F5 Dave
20th March 2009, 17:01
Um sort of the same thing in practice. A layer of plating will still create a thermal barrier, so it would be better to use untreated aluminum, (if it didn't wear of course) but the barrier is considerably less that a steel sleeve, so more heat is passed to the outside ally rather than retained in the sleeve & hence the rest of the engine.
A compromise you may think would be to make a ally sleeve & plate that, but while you have similar materials you still have a physical interface worse than the original cast over sleeve. It should still be better I imagine, but before you run down that path you would have to find the right ally, most you get in NZ aren't suitable for plating. Probably 4042 alloy, or maybe 6060 or 6261 which are suitable for anodising so should be ok for plating.
Oh dear, how can you close Pandora's box?
TZ350
20th March 2009, 18:29
The basic idea I'm sure everyone is aware of, it is in every 2 stroke book, probably even Roy Bacon's old duffer books. To get a visualization run some water through the bottom of the transfers & see where the flow is directed, - this of course is not a full dynamic model but is interesting & with later designs how this has evolved & how effective the kicks have become esp in the 2ndries. Where this flow ends up & how effective it is in containing charge by reducing kinetic energy & purifying what is left will all affect the result. Overboring or sleeving will put this to pot a bit wrt to transfers.
"kicks, esp in the 2ndries" I didn't know what F5 meant but found the answer in the pic below. I had seen them in barrels before but did not know that they were called kickers.
Scraped from MacDizzy's finding the sweet spot:- http://www.macdizzy.com/cylinder_map6.htm
The rear transfer port has both of its walls cut at 90°, but the rear wall has a different angle cut into it at the liner - a sort of kicker- to make the charge push forward. The direction of the front wall of this port would be directly in line with the opposing port (if I drew it) - so the released mixture will collide with each other. This helps to keep the fresh mixture in place and helps prevent it from exiting the exhaust port.
These port walls determine where the new mixture goes. In general terms - ports that are more directly opposite each other tend to make more peak power. Range comes from aiming the charge more rearward. The combination of these angles and the upward angles of the port roofs shows a wide range of possibilities within any engine.
The major components here are the cylinder ports size, shape and angles - both horizontal and vertical. The transfer ports of the engine have as much to do with the way the engine runs and its behavior as the exhaust pipe. It could be said that the transfer ports deliver the spread or range of power while the tuned pipe balances the delivery and availability of that power.
Read more here:- http://www.macdizzy.com/cylinder_map6.htm
.
Buckets4Me
20th March 2009, 18:34
Oh dear, how can you close Pandora's box?
buy an FXR :girlfight: :2thumbsup
TZ350
20th March 2009, 19:25
1975 was another time another place huh?
Been there done that! :rockon:
speedpro
20th March 2009, 19:59
It could be said that the transfer ports deliver the spread or range of power while the tuned pipe balances the delivery and availability of that power.
This is another thing I have played with on the dyno. I actually devconned up the boost port then dyno'd the engine. From memory it still made the same peak power but got real peaky. I then cleared the boost port amd devconned the main transfers and dyno'd again and then same procedure with the auxilliary transfer ports. I was surprised at how little differance it actually made. Having said that the engine was a troublesome wee thing it's whole life so it may not have been the best test subject.
Pudding
20th March 2009, 20:05
I have been following this thread, and found it most interesting.
SS90
20th March 2009, 20:38
This is another thing I have played with on the dyno. I actually devconned up the boost port then dyno'd the engine. From memory it still made the same peak power but got real peaky. I then cleared the boost port amd devconned the main transfers and dyno'd again and then same procedure with the auxilliary transfer ports. I was surprised at how little differance it actually made. Having said that the engine was a troublesome wee thing it's whole life so it may not have been the best test subject.
This is where it get really hard.
While there is significant power to be made, just small "errors", (a few degrees off), will have not so much catastrophic effects, but generally, you will see no gains, and can't figure out why.
Obviously, if you have a different set of auxillary ports (boost ports etc), the scavenge pattern that is best for your engine is vastly different from one with out (as they all must work together (or "match")
This is from Eric Goor.....,
Now the transfer ports are uncovered at about 120 degrees after TDC. The scavenging phase has begun. Meaning that the unburned mixture gasses are flowing out of the transfers and merging together to form a loop. The gasses travel up the back side of the cylinder and loops around in the cylinder head to scavenge out the burnt mixture gasses from the previous power stroke. It is critical that the burnt gasses are scavenged from the combustion chamber, in order to make room for as much unburned gasses as possible.
THAT IS THE KEY TO MAKING POWER IN A TWO STROKE ENGINE.
The more unburned gasses you can squeeze into the combustion chamber, the more the engine will produce. Now the loop of unburned mixture gasses have traveled into the exhaust pipe's header section. The gasses aren't lost because a compression pressure wave has reflected from the end of the exhaust pipe, to pack the unburned gasses back into the cylinder before the piston closes off the port. This is the unique super-charging effect of two-stroke engines. The main advantage of two-stroke engines is that they can combust more volume of fuel/air mixture than the swept volume of the engine. Example: A 125cc four-stroke engine combusts about 110cc of F/A gasses but a 125cc two-stroke engine combusts about 180cc of F/A gasses.
Like I said in much earlier posts, scavenge patterns are where modern two stroke developers are putting their research..... As not only does it make more power, it is also more efficient, and much lower in pollution.
Has anyone heard of the Aussie company orbital?
KTM have, and I hear that soon they will use their latest design, you can get a brief view of it here
www.orbitalcorp.com.au/orbital/directinjection/motorcycle2s.htm
Sadly, it doesn't go into to much detail, but the basics are, air is injected into the cylinder, BEFORE fuel is (to clear the cylinder), therefore obtaining a more "scavenged cylinder"
This is the best I have found on the BASIC system, like I say, their latest developments are pretty well kept secrets.
http://www.envirofit.org/direct_fuel_injection.html
speedpro
20th March 2009, 21:10
I've been to the plant in Perth and had a look around. Very interesting place. Their OCP technology is already licensed to companies round the world, like Mercury marine. It's very good on the emissions front allowing the nice simple good ol' 2-stroke to do good.
SS90
21st March 2009, 04:49
Waste heat to the cooling system is my current focus and I am interested in the practicalities of your cooling arrangements.
Do you think the shorter exhaust port tract on the Scooter reduces the heat takeup into the cooling system? The mean length of the GP125's exhaust tract is about 55mm long.
I would find it useful to know a Scooters head temperature and lower fin temperature measured near the exhaust after a good run, as a comparison. Would you measure it for me?
Because of your enthusiasm for crankcase compression ratios, induction resonance and unmasking the transfers I have become interested in looking at it again to see what more can be done with the GP.
But any practical work will have to wait for a little bit until I get to strip the motor for some gearbox maintenance that needs doing. Because of a damaged clutch nut thread I need to replace the main shaft.
.
At the risk of being labeled a Teacher again, I will just summate all the points I have raised in this thread, as these are all things that are required to keep an air cooled tuned two stroke running at reasonable temperatures...
1) scavenge patterns, get them correct for your engine, and not only will it make better power all through the range, it will also dramatically increase cylinder efficiency.
2) Compression Ratio, don't go too high. Gordon Jennings has an opening chapter called "Fundamentals", in there it talks of "flash horsepower engines", where the compression ratio is too high, so that for a few dyno runs (or laps) it goes like hell, but sharply drops off, and end up for the rest of the race having less horsepower than other competitors.
With respect, I think you engine falls into this category.
3) Correct primary compression. We have dwelled on that enough!
Remember that because you have such large port time areas, you already have a heat problem!
The high horswpower engines that I build run quite low cylinder compression, due to the fact that the first stage of devlopment showed me that what I gained when the engine was cold, I more than lost when it was hot......
You will find that high tuned scooter engines run quite low cylinder compression, and primary compression in the vicinity of industry norms.
You asked what temp one of my heads runs at.....using a lazer pointer tester, it reads 86 Deg.
This is because of the lower cylinder compression, as well as the scavenge pattern I use, rather than the forced air cooling. I assure you that a "normal" motorcycle engine, getting a clean stream of air, that is unhindered at the point of exit for the hot air (like a small frame Vespa) is far better at displacing heat.
I have attached 2 pics, the red one is a totally origonal 125cc Vespa cooling shroud, the green one is a 25 Horspower tuned engine....they have the same shroud, the tuning one has a ligher cooling fan/flywheel (for it's obvious benifits)
My opinion, if it holds any value to you, is not to worry about trying to increase the cooling ability, that's just treating the symptom, get your motor to run more efficiently (and thereby cooler), in doing so you treat the cause.
Some really clever guys build 23 plus horsepower 133cc CAST IRON disc valve engines, that are damn near indestructable... they don't have heating problems, mainly because they use the methods I have out lined here.
This is only written to help, not to ridicule, I hope it comes across that way, as that is how it is intended.
I also downloaded this on you tube just for interest...
http://www.youtube.com/watch?v=enDo5V82Oo8
TZ350
21st March 2009, 06:58
Thanks for the reply.
From SS90’s post :-
2) Compression Ratio, don't go too high. Gordon Jennings has an opening chapter called "Fundamentals", in there it talks of "flash horsepower engines", where the compression ratio is too high, so that for a few dyno runs (or laps) it goes like hell, but sharply drops off, and end up for the rest of the race having less horsepower than other competitors.
With respect, I think you engine falls into this category.
The high horswpower engines that I build run quite low cylinder compression, due to the fact that the first stage of devlopment showed me that what I gained when the engine was cold, I more than lost when it was hot......
TZ350:- This is the Taupo experience.
From SS90’s post:- You will find that high tuned scooter engines run quite low cylinder compression, and primary compression in the vicinity of industry norms.
TZ350:- What corrected cylinder compression ratio would you expect to work in my GP? What works in tuned Scotters?
I built the motor and pipe modelled on Gordon Jennings description of what could be done with an early RM125 and the cooling improvements based on the known heat load in the cooling system and ideas from air cooled aero engines.
…………………………………...
A couple of interesting lines I copied from an automotive engineering book and posted earlier.
"Engine cylinders must be cooled to maintain a lubricant film on the cylinder walls and other sliding surfaces. The cylinders, heads, pistons and exhaust valves are cooled to prevent combustion knock or destruction of these parts due to over heating.
The heat removed from the engine by the cooling system is 25% to 35% on full load and may run as high as 40% on one third load.
An increase in speed reduces the heat lost to the cooling system.
60% of the cooling flow is directed to the cylinder and 40% to the head. The permissible compression ratio and output of air cooled aero engines depends on the efficiency of cooling of the cylinder head and have long fins 25mm to 50mm closely spaced 2.5mm to 5mm."
Interesting especially the close spacing of the fins.
.
TZ350
21st March 2009, 07:33
As an experiment last Saturday at the track I held the throttle so that the carb was only part open, effectively creating about a 24mm venturi. The motor melted due to pumping losses, or something.
From a couple of lines that I posted earlier.
"The heat removed from the engine by the cooling system is 25% to 35% on full load and may run as high as 40% on one third load. An increase in speed reduces the heat lost to the cooling system."
For the fuel consumed, less energey removed from the motor as work and more as waste heat to the cooling system.
Speedpro could this be what happened?
.
Pudding
21st March 2009, 08:41
1) scavenge patterns, get them correct for your engine, and not only will it make better power all through the range, it will also dramatically increase cylinder efficiency.
"will also dramatically increase cylinder efficiency" by improved scavenging effectiveness and thereby "make better power"
Am I reading this correctly? Wouldn't this mean more waste heat to the cooling system or am I missing something? Please explain.
Chambers
21st March 2009, 10:41
My opinion, is not to worry about trying to increase the cooling ability, that's just treating the symptom, get your motor to run more efficiently (and thereby cooler), in doing so you treat the cause.
It seems people are hung up on the principal that: Make More Power = Make More Waste Heat.
Could you elaberate on "get your motor to run more efficiently (and thereby cooler), in doing so you treat the cause".
What do you mean by "more efficiently"
TZ350
21st March 2009, 10:55
I am interested in the transfer streams that SS90 talks about.
The picture and quote are from an earlier post,
"A picture of my combustion chamber after Taupo. The wash from the transfer streams can be clearly seen. If anyone can tell me anything about their shape, I would be interested to know if they look right or otherwise."
I have been looking at the way the transfers wash the piston and head to determin their flow pattern.
When I get back to work Monday I will see if I can scan the relevant pages about Janti (transfer stream) patterns and post them.
Pics to make it easy for SS90 to tell me if this is what he is talking about or maybe elaborate on them or the head with a few scketches of his own.
I feel comfortable with 2-stroke theory, practical implimentation is the chalange.
.
speedpro
21st March 2009, 12:32
From a couple of lines that I posted earlier.
"The heat removed from the engine by the cooling system is 25% to 35% on full load and may run as high as 40% on one third load. An increase in speed reduces the heat lost to the cooling system."
For the fuel consumed, less energey removed from the motor as work and more as waste heat to the cooling system.
Speedpro could this be what happened?
.
I'm gonna have to work on my "piss taking" I see. Obviously a bit too subtle for most.
It's only the percentages that change as far as heat dissipation. At full throttle we may have say 1000BTU being dissipated in the cooling system assuming for simplicity that 3000BTU is being generated when the fuel is burnt & a 33% split. At part throttle the fuel burnt may only provide 2000BTU total but the % split changes so that maybe 40% is dissipated in the cooling system. 40% of 2000BTU is 800BTU so the cooling system is dissipating less energy than before. I've simplified this example and I don't know how the %s change but hopefully you get the idea. By reducing the throttle opening my engine does not get hotter, unless the %s are changed WAY more than I would expect.
A good point has been raised about compression ratios. Through vast combined experience of many fast bucket racers we think that depending on the actual air-cooled engine involved that 14.7-15:1 (swept+trapped/trapped) is about the max for good sustained power. My current MB is running at 15.2:1 and holds good power all day on any track. My new motor supposedly will be more efficient at trapping mixture in the cylinder and because of that, even with the water-cooled head, the compression ratio has been set at a lower value. I haven't relied on experience for the new motor as I think I got to where I could using that and went for "professional" help and advice. Time will tell if it was money well spent. Supposedly I should be able to dust Nigel good and proper as the same guy designed both our motors at the same time and we had our pipes laser cut at the same time, etc etc.
TZ350
21st March 2009, 12:52
I'm gonna have to work on my "piss taking" I see. Obviously a bit too subtle for most.
Maybe not for everybody but you got me! :bleh:
Thats right, more lost from less burnt probably wouldn't exceed less lost from more burnt for max power would it, could it?
.
TZ350
21st March 2009, 17:48
Two-Stroke Porting Software.
Plan your ports with this software using Jennings and Bells principles.
Porting Calculator and Port Analyser. $16.25 USD each. Paypal accepted.
These are based on Bell's and Jennings Books, makes it easy to apply their work to your motor. The program screen can be switched between Bell or Jennings and back again as you work.
Look at them here:- http://www.porting-programs.com/
I purchased mine over the net 8 months ago using Paypal and it was available for downland within hours.
Then when I claimed my free upgrade it to was quickly available.
Do go and have a look at his site:- http://www.porting-programs.com/.
.
Yow Ling
21st March 2009, 19:37
Some stuff about fitting an aluminium sleve to an rz cylinder, not buckets but on topic. Its translated so it reads a bit spastic
http://au.babelfish.yahoo.com/translate_url?doit=done&tt=url&intl=1&fr=bf-home&trurl=http%3A%2F%2Fwww.geocities.jp%2Fuda_vance%2F am-rz250r.html&lp=ja_en&btnTrUrl=Translate
original link http://www.geocities.jp/uda_vance/am-rz250r.html
TZ350
21st March 2009, 20:25
Some stuff about fitting an aluminium sleve to an rz cylinder, not buckets but on topic. Its translated so it reads a bit spastic
http://au.babelfish.yahoo.com/translate_url?doit=done&tt=url&intl=1&fr=bf-home&trurl=http%3A%2F%2Fwww.geocities.jp%2Fuda_vance%2F am-rz250r.html&lp=ja_en&btnTrUrl=Translate
original link http://www.geocities.jp/uda_vance/am-rz250r.html
Some pics from the site, its well worth a look. Thanks Yow Ling.
SS90
22nd March 2009, 01:30
Thanks for the reply.
From SS90’s post :-
2) Compression Ratio, don't go too high. Gordon Jennings has an opening chapter called "Fundamentals", in there it talks of "flash horsepower engines", where the compression ratio is too high, so that for a few dyno runs (or laps) it goes like hell, but sharply drops off, and end up for the rest of the race having less horsepower than other competitors.
With respect, I think you engine falls into this category.
The high horswpower engines that I build run quite low cylinder compression, due to the fact that the first stage of devlopment showed me that what I gained when the engine was cold, I more than lost when it was
hot......
TZ350:- This is the Taupo experience.
From SS90’s post:- You will find that high tuned scooter engines run quite low cylinder compression, and primary compression in the vicinity of industry norms.
TZ350:- What corrected cylinder compression ratio would you expect to work in my GP? What works in tuned Scotters?
I built the motor and pipe modelled on Gordon Jennings description of what could be done with an early RM125 and the cooling improvements based on the known heat load in the cooling system and ideas from air cooled aero engines.
…………………………………...
A couple of interesting lines I copied from an automotive engineering book and posted earlier.
"Engine cylinders must be cooled to maintain a lubricant film on the cylinder walls and other sliding surfaces. The cylinders, heads, pistons and exhaust valves are cooled to prevent combustion knock or destruction of these parts due to over heating.
The heat removed from the engine by the cooling system is 25% to 35% on full load and may run as high as 40% on one third load.
An increase in speed reduces the heat lost to the cooling system.
60% of the cooling flow is directed to the cylinder and 40% to the head. The permissible compression ratio and output of air cooled aero engines depends on the efficiency of cooling of the cylinder head and have long fins 25mm to 50mm closely spaced 2.5mm to 5mm."
Interesting especially the close spacing of the fins.
.
Hmm, what compression ratio would I recommend?
That is a pretty good question, I have looked back to the beggining,and taken a look at your figures.........
Teezee's post-:
So the total dynamic ClearanceVolume is now 10cc’s at 10,000rpm
Dynamic Corrected Compresion Ratio = 6.8
Dynamic Uncorrected Compression Ratio = 13.5
Our aim was for a bit more than this.
So a couple of skims and re-measures later we had:-
The total dynamic ClearanceVolume is now 9.4cc’s
Dynamic Corrected Compresion Ratio = 7.3
Dynamic Uncorrected Compression Ratio = 14.3
My experience would suggest that the first volume was better in this situation, and perhaps even that could at times be a little high....... (I'm going to expect a bollocking here!)
SS90
22nd March 2009, 01:55
I am interested in the transfer streams that SS90 talks about.
The picture and quote are from an earlier post,
"A picture of my combustion chamber after Taupo. The wash from the transfer streams can be clearly seen. If anyone can tell me anything about their shape, I would be interested to know if they look right or otherwise."
I have been looking at the way the transfers wash the piston and head to determin their flow pattern.
When I get back to work Monday I will see if I can scan the relevant pages about Janti (transfer stream) patterns and post them.
Pics to make it easy for SS90 to tell me if this is what he is talking about or maybe elaborate on them or the head with a few scketches of his own.
I feel comfortable with 2-stroke theory, practical implimentation is the chalange.
.
This is from a very early post by Teezee (number 9 actually)-:
Thomas is working on the ports. Rear port angles up 55 degrees, secondaries 45 and mains are angled flat across the bore. All the transfer ports were made to open at the same time, 114 degrees ATDC, duration 132.
The rear port at 55 degrees is pretty much on the money (in my opinion), but where it goes amiss is-:
"And the mains angled flat across the bores"
This is going to give you a pretty crap scavenge pattern really.....because you are losing so much fuel out the exhaust (as you are "short circuiting" the loop scavenge system, by having the mains "angled flat across the bore" )
My experience suggests that with a set up like this, you are not going to get a visible pattern on the piston at all. My work has shown that when I start to get the pattern correct, it becomes more visible on the piston crown (as opposed to the piston having a uniform colour)
But, I see you have found some interesting information on the net, and it I think if you followed the things there, with some experimenting (I really suggest a dyno run or 3 now, so you have some "hard data" to compare)
I can't remember ever seeing a pronounced pattern on the head since I started getting the scavenge pattern "more on Par (with-out copying)", and always read the piston. But plenty of other people are well ahead of me........
I said this in an earlier post ( as a broad hint....)
"I would would look at HONDA race engines when it comes to quality scavenge patterns"
Having said that, I was told a while back to take a look Kart Sport patterns as well.
But I have to admit I never did, but just because I was being lazy!
SS90
22nd March 2009, 02:15
"will also dramatically increase cylinder efficiency" by improved scavenging effectiveness and thereby "make better power"
Am I reading this correctly? Wouldn't this mean more waste heat to the cooling system or am I missing something? Please explain.
Sure, logic dictates that more power will generate more heat......
But (in this context), By better power, I don't mean more "peak power", I mean "better power" (more torque in lower R.P.M is an example of this)
I have attached a picture from Gordon Jennings, this particular picture is an image used to show the effects of the different power curve achieved from a difference of "misaligned" transfers, compared to "correctly" aligned transfers.... Granted, in this context, it is "vertical" misalignment, but the gains (in terms of comparative curve shapes) are somewhat the same as the gains you will see when you have effective scavenge patterns, compared to transfers that "short circuit".
By having effective scavenge patterns, you essentially have more "cool swirling air fuel mixure" staying in the combustion chamber (and of course, less hot burned gasses sitting there, as the effective scavenge pattern has not only kept more fuel in the cylinder, it has "scavenged" the cylinder more that before. (it has helped push more hot burned gasses out)
Granted, there is a power increase, (and, as such a heat increase) but it is offset by the increased cooling of the combustion chamber.
The engines efficiency is increased.... it wastes less energy.
SS90
22nd March 2009, 02:44
I'm gonna have to work on my "piss taking" I see. Obviously a bit too subtle for most.
It's only the percentages that change as far as heat dissipation. At full throttle we may have say 1000BTU being dissipated in the cooling system assuming for simplicity that 3000BTU is being generated when the fuel is burnt & a 33% split. At part throttle the fuel burnt may only provide 2000BTU total but the % split changes so that maybe 40% is dissipated in the cooling system. 40% of 2000BTU is 800BTU so the cooling system is dissipating less energy than before. I've simplified this example and I don't know how the %s change but hopefully you get the idea. By reducing the throttle opening my engine does not get hotter, unless the %s are changed WAY more than I would expect.
A good point has been raised about compression ratios. Through vast combined experience of many fast bucket racers we think that depending on the actual air-cooled engine involved that 14.7-15:1 (swept+trapped/trapped) is about the max for good sustained power. My current MB is running at 15.2:1 and holds good power all day on any track. My new motor supposedly will be more efficient at trapping mixture in the cylinder and because of that, even with the water-cooled head, the compression ratio has been set at a lower value. I haven't relied on experience for the new motor as I think I got to where I could using that and went for "professional" help and advice. Time will tell if it was money well spent. Supposedly I should be able to dust Nigel good and proper as the same guy designed both our motors at the same time and we had our pipes laser cut at the same time, etc etc.
I particularly agree with speedpro's statement that "depending on the different two stroke engine....."
Every engine is different (depending on it design) (e.g, Crankcase (reed) induction, compared to disk valve induction) for example, and as such, different maximum cylinder compression ratios are applicable for each one, as well as exhausts, etc.
You say that "supposedly your motor will be better at trapping fuel in the Cylinder........."
That is interesting (and I believe I know how that is being facilitated)...Do you know what scavenge pattern has been applied to your new cylinder?
TZ350
22nd March 2009, 06:57
Hmm, what compression ratio would I recommend?
Teezee's post-:
So the total dynamic ClearanceVolume is now 10cc’s at 10,000rpm
Dynamic Corrected Compresion Ratio = 6.8
Dynamic Uncorrected Compression Ratio = 13.5
My experience would suggest that the first volume was better in this situation, and perhaps even that could at times be a little high.......
My current head is more this ratio and thought it to low, I will leave it for now and see what others think. Thanks for your reply based on your experience.
I used the term "Dynamic" to indicate the 1cc Clearance Volume lost to rod stretch at 10,000rpm. The compression ratio would be lower if measured statically.
.
TZ350
22nd March 2009, 07:07
This is from a very early post by Teezee (number 9 actually)-:
Thomas is working on the ports. Rear port angles up 55 degrees, secondaries 45 and mains are angled flat across the bore. All the transfer ports were made to open at the same time, 114 degrees ATDC, duration 132.
The rear port at 55 degrees is pretty much on the money (in my opinion), but where it goes amiss is-:
"And the mains angled flat across the bores"
This is going to give you a pretty crap scavenge pattern really.....because you are losing so much fuel out the exhaust (as you are "short circuiting" the loop scavenge system, by having the mains "angled flat across the bore" )
My experience suggests that with a set up like this, you are not going to get a visible pattern on the piston at all. My work has shown that when I start to get the pattern correct, it becomes more visible on the piston crown (as opposed to the piston having a uniform colour)
Your right, my motor with a flat piston was uniform in colour across the top and the other motors from Taupo with normal domed pistons and ports had visible patterns.
When I can I will draw diagrams showing the horozontal and vertical angles of the ports.
.
TZ350
22nd March 2009, 07:23
I can't remember ever seeing a pronounced pattern on the head since I started getting the scavenge pattern "more on Par (with-out copying)", and always read the piston. But plenty of other people are well ahead of me........
I said this in an earlier post ( as a broad hint....)
"I would would look at HONDA race engines when it comes to quality scavenge patterns"
Having said that, I was told a while back to take a look Kart Sport patterns as well.
But I have to admit I never did, but just because I was being lazy!
Do you mean your heads or my photo was not clear enough? I will see if there is a better photo. If I take the head of during the race day or soon after I can see a wash pattern in the crud/oil that covers the combustion chamber. It usually doesn’t last long as in handling the head it is easily wiped away. I will draw a picture.
I remember you pointing in the direction of Honda but I could not find anything??? a couple more hints would help, thanks.
.
TZ350
22nd March 2009, 11:52
This is a link to someone elses thread that talks about suspension setup:- http://www.kiwibiker.co.nz/forums/showthread.php?t=93518
After last Sundays points racing where I suffered several bad juddering front end slides. :( that effectivly detuned me for the day. It is time to start looking at handling and riding technique improvements to go with the engine development.
.
TZ350
22nd March 2009, 13:20
Thinking of building a Dyno? Check out Geoff's homebrew dyno page:- http://geoffm.sitegoz.com/dyno/DIY_dyno.html
Also a air cooled 2-stroke hotup page/links, mostly RD stuff:- http://geoffm.sitegoz.com/tuning-info.html
A link to Eric Gorrs 2-Stroke tuners page:- http://www.eric-gorr.com/2%20stroke%20top%20end%20and%20performance.pdf
Typical Kiwi ingenuity. Thanks Geoff
.
Chambers
22nd March 2009, 18:48
Um sort of the same thing in practice. A layer of plating will still create a thermal barrier, so it would be better to use untreated aluminum, (if it didn't wear of course) but the barrier is considerably less that a steel sleeve, so more heat is passed to the outside ally rather than retained in the sleeve & hence the rest of the engine.
B&S Lawn mower motors had an untreated aluminum bore with a flash chromed piston and rings. I think other motors used this idea too. The early Yamaha racers tried teflon coated bores before going to chrome.
Like B&S and Yamaha, TZ350 was thinking outside the box with his copper head idea, He is in good company.
Buckets4Me
22nd March 2009, 20:53
Check out that areo cylinder, see how close the fins are spaced compaired to the motorcycle cylinders.
Maybe more for 4-Strokes. Sparkplug pictures, worth a look:- http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html
.
SS90
22nd March 2009, 20:56
B&S Lawn mower motors had an untreated aluminum bore with a flash chromed piston and rings. I think other motors used this idea too. The early Yamaha racers tried teflon coated bores before going to chrome.
Like B&S and Yamaha, TZ350 was thinking outside the box with his copper head idea, He is in good company.
While "Thinking out of the box" is certainly cool, the copper (or bronze alloy) cylinder head is simply a serious step in the wrong direction in my opinion.
Yes, bronze alloys have great heat transfer properties......ever noticed (or measured) how much bronze alloys EXPAND when heated....now compare that to a high silicone Aluminium (such as the Japanese have been using for the last 20 or 30 years)
I think if you made a cylinder heat for your performace two stroke out of this type of material, you will be replacing the piston before too long.
Just take a look at the detonation starting around Teezee's piston in the photo's from the last race.
Look closely, and you will see a "sand blasted" effect around the outer edge of the crown....
This is detonation.
Detonation starts at the outer edge of the crown.
If this was a 125 water cooled GP bike (that had just finished a race, and hopefully won), then, you would most likely say that "you where on the limit", as far as compression ratio was, take note, and next time you where running at that track, in those conditions, lower it a little.
And ditch the piston.
However, this was caused (in my opinion), by the fact that you had the copper "liner" in the head, which, when it got hot, expanded, closed up the "squish area", and caused detonation (possibly was touching the piston at the top of the revs as well).
Have a complete head from copper, I suspect somewhat more dramatic results.
Looking at the pictures of the head after the race, the head shows the same signs of detonation.
The fact that the copper "liner" isn't pressed into the head is adding to the problem as well.
If a "cast in" cylinder liner ( like a your GP125 is) is better at displacing heat than a simple "pressed in liner", then the same logic applies in this situation.
I really believe, as has been stated much earlier on by a few people, finding an early "radial" head off the last of the air cooled motorcross bike (I.E, designed to cope with lower speeds, higher power), and adapting it too fit would be a wise move)
Buckets4Me
22nd March 2009, 21:01
Jetting through reading piston wash.
Reading Piston Wash:- http://www.bikemanperformance.com/tech_detail.php?ta=4
and even better:- http://www.snowtechmagazine.com/articles/2001/baseline/baseline.php
Ist pic Rich, 2nd pic Good, 3rd pic Lean.
SS90
22nd March 2009, 21:09
Put it on a dyno, stop pissing round. You make a change, do a run, and see exactly what effect the change has had. No bullshit, no guessing, no theories, just cold hard data.
As said by speed pro, week one!
I have to agree 100% on this. I believe that you would be much further ahead if you had done this. When you find a reliable dyno (and experienced operator), your results are always rewarding. Cool idea on building one Teezee, I have to believe though, that spend 3 hours on an existing dyno, (with established limits), as well as existing data for comparison, that you will never look back!
SS90
22nd March 2009, 21:17
Reading Piston Wash:- http://www.bikemanperformance.com/tech_detail.php?ta=4
and even better:- http://www.snowtechmagazine.com/articles/2001/baseline/baseline.php
That's not a bad page, the important thing that I am talking about with "scavenge patter", is the "shape" you get. (the "pattern"......I.E the "scavenge pattern)
Try to look for a combustion shape, that "shields" the fuel from pouring out the exhaust (after all, the extractor effect of the chamber is not 100%)
The picture on the left is heading towards one that I would aim for, if I was designing the scavenge pattern for this engine..... You will see how that exhaust side of the crown area is clean..... It's not perfect (you will never get it that way, but it's a very big step in the right direction.
TZ350
22nd March 2009, 21:55
Just take a look at the detonation starting around Teezee's piston in the photo's from the last race.
Look closely, and you will see a "sand blasted" effect around the outer edge of the crown....
This is detonation.
Detonation starts at the outer edge of the crown.
However, this was caused (in my opinion), by the fact that you had the copper "liner" in the head, which, when it got hot, expanded, closed up the "squish area", and caused detonation (possibly was touching the piston at the top of the revs as well).
Looking at the pictures of the head after the race, the head shows the same signs of detonation.
The fact that the copper "liner" isn't pressed into the head is adding to the problem as well.
If a "cast in" cylinder liner ( like a your GP125 is) is better at displacing heat than a simple "pressed in liner", then the same logic applies in this situation.
I really believe, as has been stated much earlier on by a few people, finding an early "radial" head off the last of the air cooled motorcross bike (I.E, designed to cope with lower speeds, higher power), and adapting it too fit would be a wise move)
If it comes to it could make a big radial head from some large heat sinks I have.
We have made two versions of the copper head. Version one had a 1.5mm layer of copper plazma sprayed onto and into the combustion chamber of a modified GP125 head, which I would think would make a good thermal contact, and then teamed it up with a copper fin.
The thinking with this head was that the thick copper combustion chamber shell would be better at transmitting waste heat to the outside but the tarnishing of the copper became a problem, to be solved later.
The second one is basicaly an ordinary alloy head and like before its fitted with an oversized copper head gasket that extends into the combustion chamber to form the squish band and extends out the sides to form an extra cooling fin.
With the extra cooling the copper fin gives, the head runs at a measurably lower temperature. So I recon its a Keeper. The next part of the project is to reduce the heat uptake to the cooling system from the exhaust and add some air ducting.
This engine started with a 90 main jet and now runs a 112.5. Its funny, as we developed the engine we had to keep leaning the needle and richening the main jet.
F5 Dave suggested that because jetting up now, does not seem to richen it up, the needle could be controlling the fuel on full throttle and not the main jet.
We followed his suggestions, removed the main jet, ran the bike and it bogged from 1/2 throttle on, so this tells us that the needle and needle-jet combo are ok.
Looking at the piston wash pictures its clear like you say, the GP is running lean.
I have seen the sand blasted look of detonation before, mostly in other peoples TZ's. What looks like detonation in the picture is in fact the piston touching the squish band and polishing the combustion deposits on the edges of the piston. I ran my TZ this way and it worked OK, very well in fact, but I have to be mindfull that the MSV produced suits the GP.
From the piston wash pictures its clear that I could run the bike much, much richer and the wash pattern would tell me something about the transfer stream behaviour. Then following your sugestions and what I can find out from other sources make improvements.
.
xwhatsit
22nd March 2009, 22:08
Thinking of building a Dyno? Check out Geoff's homebrew dyno page:- http://geoffm.sitegoz.com/dyno/DIY_dyno.html
Just in case people don't know, that's the member geoffm from this site. He was having a dyno run the other weekend, bring some beer and have a go on the dyno... not many people turned up.
I think he's got it just south of Auckland.
Hit him up to have a go on it! I don't want to speak for others but he seemed rather keen to have people make use of it.
TZ350
22nd March 2009, 22:28
Just in case people don't know, that's the member geoffm from this site. He was having a dyno run the other weekend, bring some beer and have a go on the dyno... not many people turned up.
I think he's got it just south of Auckland.
Hit him up to have a go on it! I don't want to speak for others but he seemed rather keen to have people make use of it.
Yes I will. Getting access to a dyno has been a bit of an issue.
.
SS90
22nd March 2009, 22:33
If it comes to it could make a big radial head from some large heat sinks I have.
We have made two versions of the copper head. Version one had a 1.5mm layer of copper plazma sprayed onto and into the combustion chamber of a modified GP125 head and then teamed it up with a copper fin.
The thinking with this head was that the thick copper combustion chamber shell would be better at transmitting waste heat to the outside but the tarnishing of the copper has became a problem, to be solved later.
The second one is basicaly an ordinary alloy head with an oversized copper head gasket that extends into the combustion chamber to form the squish band and extends out the sides to form an extra cooling fin.
With the extra cooling the copper fin gives, the head runs at a measurably lower temperature. So I recon its a Keeper. The next part of the project is to reduce the heat uptake to the cooling system from the exhaust and add some air ducting.
This engine started with a 90 main jet and now runs a 112.5. F5 Dave suggested that because jetting up does not seem to richen it up the needle could be controlling the fuel on full throttle and not the main jet.
We followed his suggestions, removed the main jet, ran the bike and it bogged from 1/2 throttle on, so this tells us that the needle and needle-jet are ok.
Looking at the piston wash pictures its clear like you say, the GP is running lean.
I have seen the sand blasted look of detonation before, mostly in other peoples TZ's. What looks like detonation in the picture is in fact the piston touching the squish band and polishing the combustion deposits on the edges of the piston. I ran my TZ this way and it worked OK, very well in fact.
From the piston wash pictures its clear that I could run the bike much, much richer and the wash pattern would tell me something about the transfer stream behaviour. Then following your sugestions make improvements.
.
O.K, I fear some "Teacher" comments again...But.....
I think because of your transfer set up ("straight across the bore"), you cannot put to much stock in your (as you say) "piston wash"
If your piston is touching the combust chamber consistantly (as you say), then you are getting detonation.
When a piston touches the head (and it was in a somewhat cooler environment, that detonation is less likely to occur.....like a water liquid cooled engine), you don't get a rough surface, (like your picture), you get "shiny" "witness marks"
The surface on your piston crown is rough. That's detonation in my experience.
Detonation is not only caused by jetting, it's caused by primarily excessive heat in the combustion chamber. (which of course lean jetting will cause as well)
This can be for dozens of reasons (too much cylinder compression, too advanced ignition, too much dynamic retard, expansion chamber design, incorrect jetting), just to name a few....there are lots more!
With your copper head "combustion chamber insert", you are having problems.....the piston should NEVER touch the head, even more so in an air cooled engine. I know of examples of people running tiny squish clearances, and at the end of the race having small witness marks from the piston to head contact, but, they won the race. And these are water cooled engines.
That was the limit of the set up FOR THE ONE RACE
I forgot about your heatsink machined into a head idea, and I think it has merit!
Just to play devils advocate, I am no scientist, (and far from it), but does anyone know how good a heat sink is at expelling heat energy to the air? I am curious, as I appreciate they are good at drawing heat away from something, but what happens then?
But, the idea really has me interested. I would be VERY interested in the results.
TZ350
22nd March 2009, 22:55
If your piston is touching the combust chamber consistantly (as you say), then you are getting detonation.
Why. Whats the mechanisim?
The surface on your piston crown is rough. That's detonation in my experience.
Your looking at a picture, when the guy on the ground says the squish area is polished its probably smart to accept it.
I forgot about your heatsink machined into a head idea, and I think it has merit!
Just to play devils advocate, I am no scientist, (and far from it), but does anyone know how good a heat sink is at expelling heat energy to the air? I am curious, as I appreciate they are good at drawing heat away from something, but what happens then?
But, the idea really has me interested. I would be VERY interested in the results.
I think that a large volume of alluminum might not "draw" the heat away from the combustion chamber nearly as well as a small volume of alluminum with fins close to the combustion chamber shell. When you think about the relative thermal gradiants you will see what I mean and why a copper combustion chamber shell looked promising.
.
TZ350
22nd March 2009, 23:09
Detonation is not only caused by jetting, it's caused by primarily excessive heat in the combustion chamber. (which of course lean jetting will cause as well)
" (which of course lean jetting will cause as well)" not so! Leaning the jetting down allows the motor to make more of the power its capable of. The waste heat from this extra power overwhelms the cooling system. It’s the inability of the cooling system to keep up that leaves excessive heat in the combustion chamber causing detonation.
.
SS90
22nd March 2009, 23:16
Why. Whats the mechanisim?
Your looking at a picture, when the guy on the ground says the squish area is polished its probably smart to accept it.
.
Well, as you know, excessive heat in the combustion chamber is the primary cause of detonation. You have stated that the Piston is touching the head, now, applying just simple logic, now, as you have stated previously, there is "stretch" in the rod at high R.P.M (giving rise to the concept of "dynamic" cylinder compression ratio, now, I am putting forth the concept, that with the addition of this new "variable" of a Combustion chamber "liner" made of Copper (and copper expands quite dramatically with heat), your "dynamic cylinder compression ratio" is increasing with not only R.P.M, BUT ALSO TEMPERATURE!
Now, in the case of a water cooled performance two stroke, due to the fact that you have far more efficient cooling of the combustion chamber, if you run such a tight squish clearance (as you know, not to be confused with "cylinder to piston clearance"), say, maybe something like 0.6mm (just as a number), and you find at say 13,000 R.P.M, the piston just "kisses" the head, you may only find a small amount of detonation (or maybe none, due to the fact that the liquid cooling keeps temperatures low enough to surpress this), and, if perhaps you might finish the race, making power the whole time, and maybe, if you overrev it too much, the detonation may not be enough to stop your fun, it may well be the ring groove compresses from the impact and "jams" your ring.
Now, have the same scenario with an air cooled engine (and the increased combustion chamber temperature this brings with it), your outcome of this scenario looks a little more "Bleak"
Yea, I have to agree, I worded that incorrectly. sorry abouot that. Your "on the ground", I'm on the other side of the world. I'm not calling you a liar, but can you take a clear picture of the crown for me, I am really confident I can see detonation....Trust me, I have seen alot in my time! DOH!:rolleyes:
Yea, I just don't know about the effect of the heat sink on a consistent temperature situation. (like prolonged operation at full throttle) Like I say, I'm REALLY keen to see some data....you never know...might try one for a scooter engine I am building for a friend...using your data as a model aye!:headbang:
Try and get some heads (of different combustion volumes), as well as one of the heat sink concept, and do some "control situation" testing on a good dyno (and a good experienced operator), then I think you will have some very specific data that will help BIG TIME!
SS90
22nd March 2009, 23:26
I have talked earlier about the "shapes" used in the case transfer areas..... this is along the right direction.....I use slightly different ones..... these particular ones are nothing new, and have been around for a while...... but I assure you there are good reasons why they are this shape...... It's not "just for volume"
:chase:
SS90
22nd March 2009, 23:57
With-out giving away too much, check out the transfer angles on this "Metra-Kit" teenage racing series cylinder...it's not the best picture (and from the wrong angle), but it's a good start!
(It's not the shape of the front transfer port that I am talking about (it's that way to allow for the auxillery exhaust port), I'm suggesting the angle they "spray into the cylinder"....
Note, they sure as duck guts aren't "straight across the bore"
SS90
23rd March 2009, 03:49
" (which of course lean jetting will cause as well)" not so! Leaning the jetting down allows the motor to make more of the power its capable of. The waste heat from this extra power overwhelms the cooling system. It’s the inability of the cooling system to keep up that leaves excessive heat in the combustion chamber causing detonation.
.
That's what I said.... you just used more words to say the same thing!
I say lean jetting will cause the cylinder heat temperature to increase (and too lean even hotter)
You just elaborated as to why!
The result is the same.
:confused:
TZ350
23rd March 2009, 05:34
" (which of course lean jetting will cause as well)" not so! Leaning the jetting down allows the motor to make more of the power its capable of. The waste heat from this extra power overwhelms the cooling system. It’s the inability of the cooling system to keep up that leaves excessive heat in the combustion chamber causing detonation.
.
From SS90:- That's what I said.... you just used more words to say the same thing!
Maybe............
Its why I have been working on the cooling system.
Attention to efficiency not doubt helps but If you want more real power you have to have more cooling capability.
.
SS90
23rd March 2009, 06:56
From SS90:- That's what I said.... you just used more words to say the same thing!
Its why I have been working on the cooling system. Good replys thanks 90.
.
Anyway,
Look forward to seeing the dyno curves..... I guess the whole point of what I have been writing is that there plenty of aircooled engines making high horsepower, and not suffering such big heat related power losses.
The solutions (in my experience) seem to be found in what I have posted.
I really am interested in seeing what power you have, as well as what your curve looks like.
As a side note, while I appreciate the fact that the peak horsepower number will vary from Dyno to Dyno, and pay little attention to that, in almost 10 years of operating various Dyno's around the place, I have personally never seen more that 17 P.S and 14 N.M (at the rear wheel) on an air cooled disc valve two stroke, running a 24mm carb.
I have probably done over 200 runs on that type of set up. (on various engines)
Number are just numbers though!
Lookig forward to it Teezeetreefiddy!:2thumbsup
F5 Dave
23rd March 2009, 09:20
TZ what do you mean by "Straight across the bore?" Do you mean viewed from the top?, or as I read it; angle of entry is horizontal across piston top? In which case where does the gas stream end up? Suzuki seemed to continue with the single transfer concept on the GP as they had on T series 70s bikes (or is my memory failing me?) long after they abandoned it in even TS engines.
Fooman
23rd March 2009, 10:34
I am putting forth the concept, that with the addition of this new "variable" of a Combustion chamber "liner" made of Copper (and copper expands quite dramatically with heat), your "dynamic cylinder compression ratio" is increasing with not only R.P.M, BUT ALSO TEMPERATURE!
Why? Are you assuming that the copper insert expands into the combustion chamber? It won't. The insert is essentially a sheet with a hole in it. As the insert warms up, the hole becomes larger, unless it is sufficiently restrained by the shear force applied by the tension in the head bolts (in which case the insert will then have thermally induced stresses). Holes in things undergoing thermal expansion get bigger, not smaller.
There is a small mis-match in thermal expansion between aluminium-silicon casting alloys and copper alloys (copper doesn't expand as much, α = 21e-6 for Al-Si, 18e-6 for Cu), but the effect will be minor, especially given the mechanical restraint.
Cheers,
FM
TZ350
23rd March 2009, 16:17
TZ what do you mean by "Straight across the bore?" Do you mean viewed from the top?, or as I read it; angle of entry is horizontal across piston top? In which case where does the gas stream end up? Suzuki seemed to continue with the single transfer concept on the GP as they had on T series 70s bikes (or is my memory failing me?) long after they abandoned it in even TS engines.
I think SS90 has misunderstood me. The main transfers are vertically flat (or very shallow) but angle back towards the rear of the cylinder. There are secondary transfers that look like add-ons and a rear boost port. When I run water through them the flow towards the rear wall. Will draw pictures and make measurements later.
.
F5 Dave
23rd March 2009, 16:26
Thought that was the case.
ahh, so there are 2ndries? I thought I had seen a GP with only main transfers. (bear in mind this was weeell over 10 years ago since I eyeballed one)
Or do you mean add ons as if someone had done it after? Are other GPs like this?
TZ350
23rd March 2009, 16:32
Well, as you know, excessive heat in the combustion chamber is the primary cause of detonation. You have stated that the Piston is touching the head, now, applying just simple logic, now, as you have stated previously, there is "stretch" in the rod at high R.P.M (giving rise to the concept of "dynamic" cylinder compression ratio, now, I am putting forth the concept, that with the addition of this new "variable" of a Combustion chamber "liner" made of Copper (and copper expands quite dramatically with heat), your "dynamic cylinder compression ratio" is increasing with not only R.P.M, BUT ALSO TEMPERATURE!
There is no way the copper expands enough to affect the compresion ratio.
I used the term "Dynamic" in my earler calculations of compresion ratio to take account of the rod streach. Thats why the ratios given are labled "Dynamic.......at 10,000rpm".
Like you say, the rod streach and how it affects a staticly measured compresion ratio is something to bear in mind.
I figure on my engine the difference between the static and dynamic clearance volumes is about 1.25cc.
The dynamic stretch for my motor is about 0.5mm and I have got pretty good at shimming the barrel so the piston just kisses the head when I want it to. I would not normally do this as it puts the MSV out but I wanted to squeeze the compression a bit for the short track and the new head.
.
TZ350
23rd March 2009, 16:49
Thought that was the case.
ahh, so there are 2ndries? I thought I had seen a GP with only main transfers. (bear in mind this was weeell over 10 years ago since I eyeballed one)
Or do you mean add ons as if someone had done it after? Are other GPs like this?
No... done by the factory and I thought they were all like this. The barrel looks like it was originally meant to have the traditional 70's Suzuki two main transfers then the marketing people said Yamaha has four, so they add secondary’s fead from the main's, and ugly it is.
.
TZ350
23rd March 2009, 17:01
I forgot about your heatsink machined into a head idea, and I think it has merit!
Just to play devils advocate, I am no scientist, (and far from it), but does anyone know how good a heat sink is at expelling heat energy to the air? I am curious, as I appreciate they are good at drawing heat away from something, but what happens then?
But, the idea really has me interested. I would be VERY interested in the results.
Sadly the heat sink idea won't work, even a big block of aluminium would not work for my bike. You probably have already thought of the reason yourself. But I will draw a pic to explain why I don't think using a heat sink or a big block of aluminium is a flyer.
The sharp peak in the picture represents the fins, the sloping line "T" represents the thermal gradient, the bottom (X) axis is the distance from the fin to the combustion chamber and the (Y) axis "T" represents temperature.
The function of the heads cooling system is to cool the combustion chamber surface.
The roots of the fins on my GP125 head are very close, as close as you can get to the combustion chamber surface "C1 in the pic" and the heat-sink combustion chamber surface "C2 in the pic" is much further from its fins and so the thermal resistance is greater and the combustion chamber surface of the heat-sink will run much hotter and be less responsive to changes in the thermal load.
A good head has a very short thermal path to the cooling system. That’s one of the reasons water cooling works so well. Air cooled heads suffer from a space problem, in trying to get sufficient fins close to the combustion chamber shell.
This is one reasion why those aero engines had such thin fins, its to pack them in.
Copper with twice the thermal conductivity or half the thermal slope (less heat resistance), looks like it could remove heat from the combustion chamber surface much more efficiently (quickly) than aluminium. This should be good for an aircooled motor or even a water cooled one if you needed too.
My conclusion:- The longer and/or steeper the thermal path to the cooling system (fins or water) the higher the temperature, will be of the combustion chamber surface!
So big heat-sinks and big blocks of aluminium are non-starters which is a pity. The only way to improve the air-cooled head is to get more or better fins closer to the combustion chamber shell. Hence the oversized copper head gasket that is also a large fin.
Works a treat!
Now to reduce the heat uptake in the exhaust and then we can work on the scavenge patterns for more and better power.
.
saxet
23rd March 2009, 17:12
[QUOTE=F5 Dave;1994293]Thought that was the case.
ahh, so there are 2ndries? I thought I had seen a GP with only main transfers.
I've seen a few GP barrels of late and they are as TZ describes.
speedpro
23rd March 2009, 19:47
Both my MBs have the transfers closest to the exhaust port at a greater angle up the bore than the rear transfers which are themselves angled up. By contrast my earlier engines had the main transfers angled flat across the piston. I thought Wobbly had made a mistake when he wrote the numbers down so I checked.
Interesting little ramp on the base of the transfers in the picture from SS90.
Chambers
23rd March 2009, 20:55
Yea, I have to agree, I worded that incorrectly. sorry abouot that. Your "on the ground", I'm on the other side of the world. I'm not calling you a liar, but can you take a clear picture of the crown for me, I am really confident I can see detonation....Trust me, I have seen alot in my time! DOH!:rolleyes:
You can take a good picture but by the time Kiwi Biker compacts it to size it loses a lot of definition.
There is half a chance TZ is familiar with what end gas detonation in the squish zone looks like.
Its the reason they put those bronze inserts there. Although bronze is not a very good thermal conductor compaired to aluminum it is used for its wear resistant properties, and to repair existing detonation damage, as they don't get eroded like aluminum does.
Just ask TZ.
.
Chambers
23rd March 2009, 21:01
Both my MBs have the transfers closest to the exhaust port at a greater angle up the bore than the rear transfers which are themselves angled up. By contrast my earlier engines had the main transfers angled flat across the piston. I thought Wobbly had made a mistake when he wrote the numbers down so I checked.
Interesting little ramp on the base of the transfers in the picture from SS90.
The primaries steeper than the secondarys, I have never seen that before could you show us a sketch of them?
.
TZ350
23rd March 2009, 21:31
Sorry SS90, I kept calling them "Janti" but they are "Jante" patterns.
An Extended Jante Test Procedure for Two-Stroke Piston-Ported Engine Development
Document Number: 941679
Date Published: September 1994
Author(s):
Dennis W. Montville
Badih A. Jawad
Abstract:
Two-stroke engine development has been occurring for many years. One of the main criteria affecting two-stroke piston-ported engine performance is scavenging, which is the process of using the incoming fresh air charge to purge the cylinder of exhaust gases. Among the simplest test procedures employed to model scavenging air flow is the "Jante" test, developed by Alfred Jante. This test was developed primarily to develop port designs for engines operating at peak power and so gives results having limited use for engines operating over a wide range. By altering the operating procedure as discussed in this paper, the Jante test can be used to provide useful information about the engine's scavenging characteristics over a wider range of engine operation. This offers a powerful tool for determining a porting design's effect on scavenging, and therefore engine performance
SAE paper:- https://shop.sae.org/technical/papers/941679
If I ever get my scanner to work I will see if I can scan the relavent pages from Dr John Dixon's book "The High Performance Two-Stroke Engine".
.
TZ350
23rd March 2009, 21:43
You can take a good picture but by the time Kiwi Biker compacts it to size it loses a lot of definition.
There is half a chance TZ is familiar with what end gas detonation in the squish zone looks like.
Its the reason they put those bronze inserts there. Although bronze is not a very good thermal conductor compaired to aluminum it is used for its wear resistant properties, and to repair existing detonation damage, as they don't get eroded like aluminum does.
Just ask TZ.
.
As well as the usual culprits of heat, ignition, compression there is the problem of mismatched squish angles between head and piston leaving a small area of gas trapped at the outer edge that gets over squished then explodes. Common problem on early TZ's
Yep, everything from the wild gnawing of rats to a mild sand blast at the edges.
As well as the usual culprits of heat, ignition, compression there is the problem of mismatched squish angles between head and piston leaving a small area of gas trapped at the outer edge that gets over squished then explodes. Common problem on early TZ's.
I am mindfull of this traped gas problem when I run the piston real close to the head.
If you think your getting light detonation look for the tell tale black pepper spots on the plug insulator. Then if you lift the head there may be a light sand blasted look on the piston in the squish zone . Heavier detonation will show up on the plug insulator as spots of aluminum blasted of the piston crown.
Yep seen a bit of it, mostly on other peoples bikes mind. ;)
.
SS90
24th March 2009, 04:33
Sorry SS90, I kept calling them "Janti" but they are "Jante" patterns.
An Extended Jante Test Procedure for Two-Stroke Piston-Ported Engine Development
Document Number: 941679
Date Published: September 1994
Author(s):
Dennis W. Montville
Badih A. Jawad
Abstract:
Two-stroke engine development has been occurring for many years. One of the main criteria affecting two-stroke piston-ported engine performance is scavenging, which is the process of using the incoming fresh air charge to purge the cylinder of exhaust gases. Among the simplest test procedures employed to model scavenging air flow is the "Jante" test, developed by Alfred Jante. This test was developed primarily to develop port designs for engines operating at peak power and so gives results having limited use for engines operating over a wide range. By altering the operating procedure as discussed in this paper, the Jante test can be used to provide useful information about the engine's scavenging characteristics over a wider range of engine operation. This offers a powerful tool for determining a porting design's effect on scavenging, and therefore engine performance
SAE paper:- https://shop.sae.org/technical/papers/941679
If I ever get my scanner to work I will see if I can scan the relavent pages from Dr John Dixon's book "The High Performance Two-Stroke Engine".
.
That would be cool to read!
I am luck enough to have been able to do some design work with the rendering program "CATIA" (Certainly not on my own, with a suitably qualified operator) when I started looking into scavenge patterns, it really did open my eyes!
I had noticed that you had spelled it wrong, it made no difference, as it was clear to me what you where talking about!
SS90
24th March 2009, 04:50
So big heat-sinks and big blocks of aluminium are non-starters which is a pity. The only way to improve the air-cooled head is to get more or better fins closer to the combustion chamber shell. Hence the oversized copper head gasket that is also a large fin.
Works a treat!
.[/QUOTE]
Yea, I was doubting the idea of the heat-sink/big block of Aluminium concept a little, but the idea was really exciting to me.
I think your research has shown it is not really feasable. (Pity really)
Just looking at the differences in piston crown condition, (from an earlier post,which was regarding 4 point (piston /cylinder temp) related seizure marks), and comparing it to the last one you posted, I just see a totally different combustion chamber condition.
As you said, you have too much heat in your exhaust port area (I think, from the picture, as it's hard to tell (obviously), that this is evident by the colour of the crown on the exhaust side.
Now, obviously, due to the fact that you have such a large port time area, there is significant heat generated in this local area, but it is more pronounced on the second picture, and, the condition of the copper combustion chamber (to me) looks very "distressed"
Of course, having said that, I have never seen a copper combustion chamber insert of this type on any two stroke engine in my life, so how can I comment!:laugh:
I have read a post that Fooman has made, and while he states a good case that my theory of the copper expanding and reducing the clearance further is wrong, I remain strong in that idea!
SS90
24th March 2009, 05:13
Why? Are you assuming that the copper insert expands into the combustion chamber? It won't. The insert is essentially a sheet with a hole in it. As the insert warms up, the hole becomes larger, unless it is sufficiently restrained by the shear force applied by the tension in the head bolts (in which case the insert will then have thermally induced stresses). Holes in things undergoing thermal expansion get bigger, not smaller.
There is a small mis-match in thermal expansion between aluminium-silicon casting alloys and copper alloys (copper doesn't expand as much, α = 21e-6 for Al-Si, 18e-6 for Cu), but the effect will be minor, especially given the mechanical restraint.
Cheers,
FM
O.K, you make a valid point.
I am still strong in my opinion though.
Way back (my first post), I talked about the idea of "wasted studs", and the reason they where used (pretty much all high performance engines, 2 stroke or other wise), since the 80's
The reason was to stop "cylinder crush"
I later gave an example of the first "Denco" built air cooled V-twin, suffering this problem, and wasted studs remedied it.
Could it be said the the "unwasted studs provided too much "mechanical restraint" (for the situation).....?????
It's generally accepted that a hot running air cooled engine will expand (if allowed by the studs expanding to do so) up to .5 of a millimeter (from room temperature, to "full heat" (or say Normal operating temperature in a racing engine)
If the studs ARE able to expand, I surmise that the "dynamic compression ratio" is somewhat less than if the expansion of the studs was not permissible (when you consider the stretch of the rod at high R.P.M is the cause of this increase.
If the studs are very thick, and do not allow this expansion, then something must give..... the outcome is usually the cylinder "squashing".
(being "pulled down", and therefore "out of round" as well.)
Now, here we have an engine, making much more power (and temperature) than was ever designed by the boys at Suzuki.
I am pretty sure that the cylinder is getting "squashed" (from other pics I have seen, as well as plenty of experience with such problems.)
Teezee even states he has a temperature problem in the exhaust area.... I suspect more now than with the aluminium only head!
(I haven't only been tuning scooters...... there was a selection process I went through to get this job!.... Experience and qualifications where mandatory)
I respect the figures you posted, and that's cool, but I just feel from what I see (and have experienced) that the copper is causing problems......
Again, I am not the "man on the ground"
If Teezee has the spare time, perhaps we can get some detailed pics?
SS90
24th March 2009, 05:19
Both my MBs have the transfers closest to the exhaust port at a greater angle up the bore than the rear transfers which are themselves angled up.
I think you could be on to something there!
:niceone:
koba
24th March 2009, 07:36
I don't think the idea that the copper expanding and tightening up the squish clearance sounds right but...
We know the copper absorbs and transfers heat better so could it be gettting really hot on the inside and acting as a bit of a glowplug?:shit:
There is debate over whether it is detonating or not but is the idea worth considering?
SS90
24th March 2009, 08:06
I don't think the idea that the copper expanding and tightening up the squish clearance sounds right but...
We know the copper absorbs and transfers heat better so could it be gettting really hot on the inside and acting as a bit of a glowplug?:shit:
There is debate over whether it is detonating or not but is the idea worth considering?
Yea, I'm "big enough" to admit when I'm wrong, it's just when you look at the picture of the "copper insert head", after the last meeting...... it looks like detonation damage to me....
In the area if approx. 8 O'clock, and about 11 O'clock
I could be wrong on the expansion concept, happy to admit it if so..... IF it is detonation, it could also be because it is so soft, and as such less detonation resistance (as has been pointed out by others)
Note, sorry about the low res, I use mac, and can magnify in hi res, but if I save it, I can't upload it here, the site doesn't allow TIFF files!
I had to take a picture of my screen with my phone!
SS90
24th March 2009, 08:38
Again, my screen has higher res, but that's my reason I say I can see detonation.....
TZ350
24th March 2009, 08:48
Again, my screen has higher res, but that's my reason I say I can see detonation.....
Looking at your pictures I can see what you mean. I will take a closer look tonight.
Ok, Its still daylight, Ive put my glasses on and using a good torch I am looking at the piston and head. I have found the marks you can see in the photo's and they turn out to be small impact craters from debris squished between the head and piston. Looking closely I can see the crater and the raised up edges which are polished from contact with the head/piston. Not surprising really as the motor was running nil or very little clearance.
The piston top is rough as it is not machined at all, it is still in its as cast state. The edges are lighter as they have been just touching the head. They have a greasy feel to them from cooked residual oil. The centre of the piston is a grey/light brown and dusty, I can rub it of with my finger leaving a hard brown surface on the piston.
The black areas at the top of the combustion chamber picture are over the exhaust port and looked real bad. At first I thought the copper had overheated as this is what copper looks like when its annealed. But then I found I could wipe it of and it was burnt but not charred oil. The oil stain looked like the (small) stain you like to see on the underside of the piston crown. Different oils they all behave and stain differently, I favour Motel T800 myself but the Team have chosen to use Castrol and I am not that familiar with what it should look like.
It was not detonating but probably was close and certainly has got very hot like you describe. Hot over the exhaust from the short working stroke and therefor hotter exhaust gas and a mixture that could usefully be a little richer.
Close one I reckon. But copper saved the day :niceone: well maybe.................
.
TZ350
24th March 2009, 11:03
This is a good read:- http://www.2stroke-tuning.nl/media/pdfjes/porting.pdf
Its about Jante patterns and Port Shape. Can be down loaded and printed.
Here is a little bit of a gold mine:- http://www.2stroke-tuning.nl/media/
Port maps etc, some of its in German.
.
Buckets4Me
24th March 2009, 18:28
Looking at your pictures I can see what you mean. I will take a closer look tonight.
Ok, Its still daylight, Ive put my glasses on and using a good torch I am looking at the piston and head. I have found the marks you can see in the photo's and they turn out to be small impact craters from derbs squished between the head and piston. Not suprising realy as there the motor was running nill or very little clearance.
.
it's lucky that you run a good air filter then isn't it :whistle:
I found an answer to all your problems
first you hit it with a big hammer
if that dosent work hit it with a bigger hammer
if that dosent work it's got to be an electrical fault :argh:
any way back to it. Will ring John very soon
TZ350
24th March 2009, 18:55
it's lucky that you run a good air filter then isn't it :whistle:
Air filter, whats that ?????????
I found an answer to all your problems
first you hit it with a big hammer
if that dosent work hit it with a bigger hammer
if that dosent work it's got to be an electrical fault :argh:
Thats right! it works for me every time.
any way back to it. Will ring John very soon
That would be great, :soon: as, maybe the weekend? I will bring all the team bikes so we can compair.
.
SS90
24th March 2009, 20:01
Looking at your pictures I can see what you mean. I will take a closer look tonight.
Ok, Its still daylight, Ive put my glasses on and using a good torch I am looking at the piston and head. I have found the marks you can see in the photo's and they turn out to be small impact craters from debris squished between the head and piston. Looking closely I can see the crater and the raised up edges which are polished from contact with the head/piston. Not surprising really as the motor was running nil or very little clearance.
The piston top is rough as it is not machined at all, it is still in its as cast state. The edges are lighter as they have been just touching the head. They have a greasy feel to them from cooked residual oil. The centre of the piston is a grey/light brown and dusty, I can rub it of with my finger leaving a hard brown surface on the piston.
The black areas at the top of the combustion chamber picture are over the exhaust port and looked real bad. At first I thought the copper had overheated as this is what copper looks like when its annealed. But then I found I could wipe it of and it was burnt but not charred oil. The oil stain looked like the (small) stain you like to see on the underside of the piston crown. Different oils they all behave and stain differently, I favour Motel T800 myself but the Team have chosen to use Castrol and I am not that familiar with what it should look like.
It was not detonating but probably was close and certainly has got very hot like you describe. Hot over the exhaust from the short working stroke and therefor hotter exhaust gas and a mixture that could usefully be a little richer.
Close one I reckon. But copper saved the day :niceone: well maybe.................
.
O.K then,
Perhaps you need to look at hardening the copper (similar process to annealing)..... the Egyptians where hardening copper axes "back in the day" (not sure what their buckets where made of though) :laugh:
You can get a cylinder head temp sensor unit that goes under your plug (like the det counter ones), and my experience is that they work well, Kart shops normally sell them.
Would be useful in future dyno tests.
SS90
24th March 2009, 20:47
Also, you wrote (quote).... "It was not detonating but probably was close and certainly has got very hot like you describe. Hot over the exhaust from the short working stroke and therefor hotter exhaust gas and a mixture that could usefully be a little richer."
The exhaust port area of the crown certainly looks hotter than previous pictures (same working stroke, same exhaust, same exhaust port areas)... what do you attribute that to?
I don't think a little richer would solve this particular problem.(although, just looking at the colour it could use a slightly bigger main jet) along those liknes, I am of the opinion that reducing your "static retard" would assist dramatically.
That would help, but certainly not eliminate the problem. I believe that would also have a flow on effect of reducing overall combustion chamber temperature as well.
Certainly only one piece of the puzzle.
SS90
24th March 2009, 20:56
Are the "holes" in the head from debris ingression as well?
TZ350
24th March 2009, 21:40
Are the "holes" in the head from debris ingression as well?
I didn't actually hold the head over the piston and match the marks up but I expect that a mark on the piston would have a matching mark on the head.
Also the piston has a small dish in it and the squish band flat area is only 4mm wide. You can see the flat outer edge which is lighter in colour and the dish is a darker grey.
.
TZ350
24th March 2009, 22:17
Gordon Blair, "The Basic Design of Two Stroke Engines" 41MB PDF, it takes a while to load:-
http://sauvegarde.cerbernetic.com/Marc/Litterature/The_Basic_Design_of_Two_Stroke_Engines_1560910089. pdf
.
craisin
25th March 2009, 02:45
sounds like the piston crown and head are taking on heat thru irregularities on their surfaces.
And I am sure back there ^^^^^ somebody has mentioned that polishing these surfaces is a good move
SS90
25th March 2009, 02:58
I didn't actually hold the head over the piston and match the marks up but I expect that a mark on the piston would have a matching mark on the head.
Also the piston has a small dish in it and the squish band flat area is only 4mm wide. You can see the flat outer edge which is lighter in colour and the dish is a darker grey.
.
Sorry, didn't quite make my question clear!
What I meant to say, was there are TWO areas on the cylinder head with different looking conditions on them, and, best as I can see (and from what you write) there is only ONE area with Marks on the piston.
Where as, on the combustion chamber, there are TWO clear areas (It's logical to suggest that one is the exhaust port area!)
So, my experience would suggest IF this is the case, then while one area of damage can be attributed to "small hitch hikers",(the area with marks on the piston, and the head) then the area with only marks on the head (not corresponding with any marks on the piston), would indicated something quite different.
Especially considering the fact that copper has such low detonation induced damage resistance (somewhat lower than the hi-silicone piston)
Thanks to the Missus, I have learned how to convert the TIFF files to JPEG (just learning what everyone else knows there I guess:whistle:)
And I hope they are as clear when I post them.
Teezee, I may be seeming to come off as pedantic, but I have a personal and professional interest here!
I'm just questioning the concept so I can learn about it's suitabilty!
IF it is as I suspect (going only by photo's), than there is a good chance that the copper is too soft (and as such, the detonation resistance is too low) for the job.
I respectfully suggest that detonation on a copper surface would look different to detonation on an aluminium (piston/aluminium head) surface.
This idea gains a little weight (in my eyes) when you add into the equation that "the piston is touching the head".... perfect environment for detonation I would suggest!
The first picture some of the marks could be attributed to "particles" being crushed (normally, in my experience showing a uneven "star" type shape, (much like a sandfly on your visor)
Not all the damage has the same appearance though, as some are "almost perfect craters"
I have seen a situation where a piston was used that was too low in detonation resistance (quite the opposite of this engine, as I believe the insert is now the "weak link"), and the detonation showed itself as "tiny little (almost) perfect "craters".
Exactly like what I see in some parts of pic 1, and all of pic 2
I surmise this type of detonation is indicative of contrasting detonation resistant materials.
If the "copper lined" head is indeed causing the cylinder head temperature to decrease, perhaps you could just lower the compression ratio (and stop the piston touching the head....ahem...) and this would stop the detonation, and still have the effect of keeping the combustion chamber cooler (even more so with the lower compression)
I am starting to think that if it is set up correctly (find the right compression ratio that is suitable for the situation)
then there is a chance that there is a tangible benefit to this concept.
Either that, or find a way to make the copper more detonation resistant.
Starting to like the idea though.....
Oh yea, the reason I surmised the copper was expanding at taking up squish clearance was I think it is safe to assume that Teezee would not assemble an engine that would have the piston touching the head!
craisin
25th March 2009, 03:12
smooth surfaces = less cling-ons or hitch hikers.
TZ350
25th March 2009, 05:39
Back to the shed tonight with glasses, torch and magnifying glass. :blink:
Wenever will I get time to read: Gordon Blair,
"The Basic Design of Two Stroke Engines" 41MB PDF, it takes a while to load:-
http://sauvegarde.cerbernetic.com/Ma...1560910089.pdf
.
craisin
25th March 2009, 06:47
is the magnifying glass to find the glasses when you lose them.
:laugh: with me the $2 shop is just down the road.
and I find the old one after I bought some more
TZ350
25th March 2009, 06:49
Ok, Looked at the head again very carefully. Matched all marks up top to bottom, all mechanical damage, no signs of detonation.
SS90 if you want to explore the copper detonation thing further, make a copper fin of your own, it's easy enough. But don't forget to tell people you saw it here first!
Time for me to settle down with a good book:- Gordon Blairs
"The Basic Design of Two Stroke Engines" 41MB PDF, it takes a while to load:-
http://sauvegarde.cerbernetic.com/Ma...1560910089.pdf
.
TZ350
25th March 2009, 07:22
.
The Relationship Between Port Shape and Engine Performance for Two-Stroke Engines
Document Number: 1999-01-3333
Date Published: September 1999
Author(s):
Hisatoshi Kinoshita - Yamaha Motor Co., Ltd.
Yuh Motoyama - Yamaha Motor Co., Ltd.
Abstract: :eek: Measurement using a three-dimensional anemometric tester was made for the gas flow inside the cylinder of a two-stroke engine while the shape of the transfer port was modified. The relationship between port shape and engine performance was investigated for various factors that characterize the flow in cylinder. In this paper, we focused mainly on two engine running conditions: the maximum output at 11,750 rpm and the output at 10,000 rpm. As a result, we found that the maximum output is most related to the tangential inclination angles of the main transfer port and the inner vent radius of the main transfer duct.
This paper can be read/printed here:- http://www.2stroke-tuning.nl/media/pdfjes/porting.pdf
In case you missed it earlier. Here is a little bit of a gold mine:- http://www.2stroke-tuning.nl/media/
Port maps etc, some of its in German.
.
Yow Ling
25th March 2009, 11:08
.
In case you missed it earlier. Here is a little bit of a gold mine:- http://www.2stroke-tuning.nl/media/
Port maps etc, some of its in German.
.
The gold mine is great, good find
TZ350
25th March 2009, 19:02
.
Walter Kaaden on developing the racing MZ with which the Suzuki GP125 has many similarities.
“Kaaden says that to be fully effective the squish band on the cylinder head
should have no clearance. Otherwise it creates what he calls ‘dead space’.
But he found that "at high revs the dynamics of the piston pushes the crown
beyond the original limit. So you must have clearance.”
The rest can be read here:- http://www.mcinternet.dk/asp/debat/debat.asp?msgID=247634
Its what I have been able to do.
Set up the piston clearance so under dynamic conditions there is no "dead space", just like Walter Kaaden.
Tuners now know that some dynamic clearance is often necessary to get the correct MSV (Mean Squish Velocity), but it is optional just as having no "dead space" is optional.
Its all in how you choose your compromises on the day.
Does anyone know if Walter had a dyno? :scratch:
.
Buckets4Me
25th March 2009, 20:50
.
Does anyone know if Walter had a dyno? :scratch:
.
yes he did
it was sowen into the back of his pants :2thumbsup
SS90
26th March 2009, 03:54
.
Does anyone know if Walter had a dyno? :scratch:
.
:lol: Of course he did..... how else would they (MZ) been able to claim the rights to breaking the 100 H.P per liter title with a 13 H.P 125cc in 1954.....It wasn't using an "ass Dyno!"
TZ350
26th March 2009, 07:32
:lol: Of course he did..... how else would they (MZ) been able to claim the rights to breaking the 100 H.P per liter title with a 13 H.P 125cc in 1954.....It wasn't using an "ass Dyno!"
Wooops, :laugh: the Walter Kaaden artical intro is in Dutch the body is in English:-
http://www.mcinternet.dk/asp/debat/debat.asp?msgID=247634
Yes he must have tested it on a dyno later, but I think all his early work was done without one.
More from the Walter Kaaden artical:-
"Working out the exact details meant years of painstaking experiment for
Kaaden and his team. With only basic facilities and no additional funds,
every change had to be assessed on the track. Fixing exhaust pipes with
spring clips was originally an MZ idea, a quick way of replacing any number
of variations of exhaust system.
"Later we had an oscilloscope for measuring the pressure of the wave going
down the exhaust and back," recalls Kaaden. "Earlier it might take 50 or 60
attempts before we arrived at the right answer. Afterwards it was only
necessary to have four or five attempts."
:lol: Of course he did..... how else would they (MZ) been able to claim the rights to breaking the 100 H.P per liter title with a 13 H.P 125cc in 1954.....It wasn't using an "ass Dyno!"
known mass, acceleration and time over a measured distance. Anyone can do it, no optomistic dyno's involved.
.
F5 Dave
26th March 2009, 08:33
Here is a fairly recent picture of Kaaden. This morning she said Meow, mumbled something about thermodynamic systems & scarfed some biscuits before finding a sunny spot to nap.
SS90
26th March 2009, 08:53
known mass, acceleration and time over a measured distance. Anyone can do it, no optomistic dyno's involved.
.
Yes, I have to agree, some Dyno's really do show some optimistic results, and (to a certain extent, price is not always a guarantee of quality, and accuracy)
I have personally inadvertantly caused strange readings by having the data box too close to the RPM inductive pick up (causing the correction factor to defuault to 80 Deg dyno room temp), making the correction factor read strange. (see attached pic)
Correction factor 1.136, and ambient air temp 80 Deg...... I DON'T THINK SO! :no::no:
As always, it's important to have a good dyno operator (with good data to reference from.)
I don't mind using Dos based dyno's with no Correction factors, the numbers are somewhat absrtact, but if it is well maintained, they seem to read consistently.... A few years ago I know that a dyno was tested (when it was built) using a particular bike, the bike wasn't used much, and 5 years later, when retested (unchanged) the curve was EXACTLY the same, right down to the H.P
Good for developing in my book!
That said, with technology now, and a clever programme writer (and experienced operator), all "bugs" seem to be a able to be over come.
SS90
26th March 2009, 09:05
known mass, acceleration and time over a measured distance. Anyone can do it,
.
Of course, that will only give you torque, but yes, it's the basics!
Buckets4Me
26th March 2009, 11:59
Of course, that will only give you torque, but yes, it's the basics!
so we know how to get torque (known mass, acceleration and time over a measured distance.)
now how do you get horse power (whats the maths)
in my maths book it had a horse lifting a weight. cant remember the figues involved thow ?
just whant to know the maths ???
is it something like Torque /mass over time or there about's ????
TZ350
26th March 2009, 12:42
.
Of course, that will only give you torque, but yes, it's the basics!
............1/4 mile standing start.
Calculate HP From ET and Weight
HP = (Weight / ((ET/5.825)^3))
Calculate HP From MPH and Weight
HP = (((MPH / 234)^3) * Weight)
.
TZ350
26th March 2009, 13:13
Calculating Horsepower from Quarter-Mile (or any other measured distance) Elapsed Time and Speed
You can also calculate your horsepower from quarter-mile passes (or any other measured distance).
There are about a zillion horsepower calculators online, and almost all of them are based on a simple formula.
It's as simple as elapsed time divided by 5.825.
That result is cubed (multiplied by itself 3 times) then the vehicle weight is divided by the result.
Just like Walter Kaaden, this is how Thomas has been developing the bikes.
.
bucketracer
26th March 2009, 19:22
:lol: Of course he did........It wasn't using an "ass Dyno!"
From TZ's post:- http://www.mcinternet.dk/asp/debat/debat.asp?msgID=247634
"Working out the exact details meant years of painstaking experiment for
Kaaden and his team. With only basic facilities and no additional funds,
every change had to be assessed on the track. "
Now we know Walter did not have a dyno, or not in the early years.
.
SS90
26th March 2009, 20:15
so we know how to get torque (known mass, acceleration and time over a measured distance.)
now how do you get horse power (whats the maths)
in my maths book it had a horse lifting a weight. cant remember the figues involved thow ?
just whant to know the maths ???
is it something like Torque /mass over time or there about's ????
From Wikipedia.:-
Only torque and speed can be measured; Power must be calculated from the torque and speed figures according to the formula:
Where K is determined by the units of measure used as can be seen below:
To calculate power in horsepower (hp) use:
where:
Torque is in pound-feet (lbf·ft)
Rotational speed is in revolutions per minute (rpm)
To calculate power in kilowatts use:
HP=TORQUE MULTIPLIED BY R.P.M DIVIDED BY 5252
where:
Torque is in newton-metres (N·m)
Rotational speed is in revolutions per minute (rpm)
(On graphs of torque vs. rpm the numerical values of torque and power are always equal when the rpm value is equal to the constant, K. The numerical values of horsepower and lbf·ft of torque are always equal at 5252 rpm because 5252 rpm in the numerator cancels out the constant, 5252, in the denominator leaving only the torque figure equal to the power figure.)
So, measure the Torque with an (inertia Dyno) then, to find out the horsepower, simply find a point on the graph Axis (Torque times R-P-M, and divide it by the constant 5252), do this for every point on the graph, and you have a horsepower curve, to go with your Torque curve.
Correction factors not withstanding.
SS90
26th March 2009, 20:24
.
............1/4 mile standing start.
Calculate HP From ET and Weight
HP = (Weight / ((ET/5.825)^3))
Calculate HP From MPH and Weight
HP = (((MPH / 234)^3) * Weight)
.
Erm, yes, I can also paint the walls in my house by putting a grenade in a bucket full of paint, and there will be paint on the walls.
But it's not very accurate.
What about the constant variable of the wind acting against the rider. Very important on a bike with a low BMEP (Like yours)
I'm afraid that none of these methods will give you any useable data when it comes to developing an engine.
You can't beat the readability of a dyno curve!
SS90
26th March 2009, 20:39
From TZ's post:-
Now we know Walter did not have a dyno, or not in the early years.
.
Yes, while not in the early years (it would seem), it would be very unrealistic to assume that someone like Kaadens, a big part of MZ's GP winning succes, did not use a dynometer. While Teezee's equations may well be correct (from a mathmatical perpesctive. Think of this.
Head wind, or tail wind. Or side wind, Or no wind.
Just getting a horsepower figure doesn't mean anything.
You have to graph it.
Dyno's are not a giant "fruit machine"
When you develop an engine, you look for the shape of a curve. You look for when you have maximum torque (what RPM), and how long you make the torque for. Same with peak power....how long are you making peak power for? You measure your exhaust gas temperature, and try to ascertain if you are going the right way with exhaust design. (some exhausts get hotter and hotter, and if you where in a 5 lap race it O.K, but after say 25 laps, you can overheat your engine, just from the wrong pipe design.)
gav
26th March 2009, 20:52
Just getting a horsepower figure doesn't mean anything.
You have to graph it.
Nah, you have to ride it mate! :scooter:
Buckets4Me
26th March 2009, 21:28
Horsepower is defined as work done over time. The exact definition of one horsepower is 33,000 lb.ft./minute. Put another way, if you were to lift 33,000 pounds one foot over a period of one minute, you would have been working at the rate of one horsepower. In this case, you'd have expended one horsepower-minute of energy.
http://www.web-cars.com/math/horsepower.html
Even more interesting is how the definition came to be. It was originated by James Watt, (1736-1819) the inventor of the steam engine and the man whose name has been immortalized by the definition of Watt as a unit of power. The next time you complain about the landlord using only 20 watt light bulbs in the hall, you are honoring the same man.
To help sell his steam engines, Watt needed a way of rating their capabilities. The engines were replacing horses, the usual source of industrial power of the day. The typical horse, attached to a mill that grinded corn or cut wood, walked a 24 foot diameter (about 75.4 feet circumference) circle. Watt calculated that the horse pulled with a force of 180 pounds, although how he came up with the figure is not known. Watt observed that a horse typically made 144 trips around the circle in an hour, or about 2.4 per minute. This meant that the horse traveled at a speed of 180.96 feet per minute. Watt rounded off the speed to 181 feet per minute and multiplied that by the 180 pounds of force the horse pulled (181 x 180) and came up with 32,580 ft.-lbs./minute. That was rounded off to 33,000 ft.-lbs./minute, the figure we use today.
Buckets4Me
26th March 2009, 21:32
Put into perspective, a healthy human can sustain about 0.1 horsepower.
Most observers familiar with horses and their capabilities estimate that
Watt was a bit optimistic; few horses could maintain that effort for long.
so I add about 0.1 hp to the bike (if I'm fit and well):niceone:
TZ350
26th March 2009, 21:43
.
Just shows you what Kaaden achieved with so little, you have to admire it.
I like SS90's idea for painting the room, a handgrenade in a bucket of paint, now thats a "Real Bloke's" way of doing it.
Bert Munro would have been impressed!
Lots of Bert Vido clips here:- http://video.google.com/videosearch?hl=en&q=Bert+Munro&um=1&ie=UTF-8&ei=lFDLSd71GoKOsQOL9dmgCg&sa=X&oi=video_result_group&resnum=4&ct=title#
.
saxet
26th March 2009, 22:56
:argh:
.
Bert Munro would have been impressed!
.
Bert Munroe..now there was a guy to admire. Sometimes as mad as a fruit bat but in a clever way!
SS90
26th March 2009, 23:05
[QUOTE=TZ350;1999917].
Just shows you what Kaaden achieved with so little, you have to admire it.
One thing in particular that Kaaden and MZ team are credited for is the "clip section" system of chamber sections.
I must say that was (is) a really good way of developing exhausts.
And, as you have pointed out, it would appear "born of necessity"
Brian d marge
27th March 2009, 02:51
Yes, I have to agree, some Dyno's really do show some optimistic results, and (to a certain extent, price is not always a guarantee of quality, and accuracy)
I have personally inadvertantly caused strange readings by having the data box too close to the RPM inductive pick up (causing the correction factor to defuault to 80 Deg dyno room temp), making the correction factor read strange. (see attached pic)
Correction factor 1.136, and ambient air temp 80 Deg...... I DON'T THINK SO! :no::no:
As always, it's important to have a good dyno operator (with good data to reference from.)
I don't mind using Dos based dyno's with no Correction factors, the numbers are somewhat absrtact, but if it is well maintained, they seem to read consistently.... A few years ago I know that a dyno was tested (when it was built) using a particular bike, the bike wasn't used much, and 5 years later, when retested (unchanged) the curve was EXACTLY the same, right down to the H.P
Good for developing in my book!
That said, with technology now, and a clever programme writer (and experienced operator), all "bugs" seem to be a able to be over come.
Me mate Dan ( Royal Enfield , no1 Ama plate ...bought a dyno ....lets just say it was a steep learning curve before he could use it as a development tool, as with a lot of engineering , the numbers ,..... well ..lies and damn statistics.....they are good for early development , cad , fea/cfd are a big help, reducing the time for development....but these at the end of the day are still educated guesses,,,,
On a fun note ...ipod/phone has a pocket dyno ..which uses ....gps ,,,,here are the results from the train from tokyo to fujimi ,,,,
max accel 0.18 g
max dist 284.91m
max velocity 83.09 kmph
0~100m = 18.63 sec
0~25kmph = 12.61 sec
0~50 kmph = 22.71 sec
max power needed weight ..... ( i tried to est ,,, 8 cars , 60 people per car ....around 55 000 kg .....i get 276 hp ..for the train .....assuming the units are imperial )
Still a bit of a giggle .....
Stephen
craisin
27th March 2009, 05:47
mmm ipod will go wwith your mac SS
Buckets4Me
27th March 2009, 05:51
seems to me that HP is the amount of work an bike can do
so you need to load the bike up with weights till it wont pull
them along any more and you have gone past the hp of the bike
you then need to remove the weights till the bike can just pull them
and it gives you an idear of the hp
you then mod the bike till it can pull more weight (means yyou have more
horse power) :apint:
SS90
27th March 2009, 06:30
:bash:
seems to me that HP is the amount of work an bike can do
so you need to load the bike up with weights till it wont pull
them along any more and you have gone past the hp of the bike
you then need to remove the weights till the bike can just pull them
and it gives you an idear of the hp
you then mod the bike till it can pull more weight (means yyou have more
horse power) :apint:
Well, a Lecturer taught me this.... If you see Torque as how hard a Boxer punches, think of Horsepower as how fast he hits..... Which was the opposite of how I just explained it to him... Made sense to me at the time..... wish he didn't hit me so damned hard though (I got it the first time.....):bash:
Remember though Buckets4me, it's not just a Horsepower figure that Teezee needs, he is looking for the Horsepower and torque curves.... they (the curves) are what best represents the BMEP of an engine.
It is possible to build an tune an engine that has high horsepower (GREAT!), but the power ends so abruptly ("PEAKY"), that it is hard to ride, and changing from one gear to another (say 3rd to 4th), means there is too bigger a jump in the gear ratios, and it "falls too far below the power", leaving a huge "flat spot".
This is why "close ratio" gearboxes exsist!
This is why you pay careful attention to the shape of the curve, and always try to have the Torque (and power) curves as long and flat as possible.
Many is the tuner who has found it benificial to drop a horse power or 2 in order to make changes that enable a flatter longer torque or horsepower curve.
Chambers
27th March 2009, 07:14
Erm, yes, I can also paint the walls in my house by putting a grenade in a bucket full of paint, and there will be paint on the walls.
But it's not very accurate.
Sorry it does not happen you don't watch Mythbusters
craisin
27th March 2009, 07:47
hey if a bike had 20 HP and you hooked up 20 horses to the back of the bike :stupid:even if the horse were dead you wont win
SS90
27th March 2009, 08:04
hey if a bike had 20 HP and you hooked up 20 horses to the back of the bike :stupid:even if the horse were dead you wont win
I think that' sthe funniest thing I have heard all year! Can I use that? It's great!
:laugh::laugh::killingme:killingme
Buckets4Me
27th March 2009, 11:59
hey if a bike had 20 HP and you hooked up 20 horses to the back of the bike :stupid:even if the horse were dead you wont win
if I was on poll I bet you would have a hard time getting past :jerry:
I'm calling the spca again :spanking:
cant have you teasing the dogs like that
dragging food around the place
TZ350
27th March 2009, 12:11
Just getting a horsepower figure doesn't mean anything.
"It Does" if your MZ has just broken the 100HP per Litre barrier then you can brag about it.
.
TZ350
27th March 2009, 14:28
Spectrum
The largest suppler of used motorcycles out of Japan.
100% Kiwi owned.
Check them out:- http://www.trade.co.jp/index.html
Get your next super Bucket FXR Aprilia TZR or whatever from here.
.
craisin
27th March 2009, 17:42
Sorry guys :whistle: Ive had a few discussions about horsepower in my life.
And that was invented some years ago to combat a guy who had a 350 hp chev and the only thing faster was his mouth.
I was only joking and didnt mean to target it at anybody.
Sure SS use it I regard you as a friend.
Buddha#81
27th March 2009, 20:07
Spectrum
The largest suppler of used motorcycles out of Japan.
100% Kiwi owned.
Check them out:- http://www.trade.co.jp/index.html
Get your next super Bucket FXR Aprilia TZR or whatever from here.
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Good site, but the only "bucket" eligble bike was a CBR150 for $4250.00 :eek5:
TZ350
27th March 2009, 20:30
Good site, but the only "bucket" eligble bike was a CBR150 for $4250.00 :eek5:
Whattttt the robbing basterds. :(
SS90
27th March 2009, 20:33
Sorry guys :whistle: Ive had a few discussions about horsepower in my life.
And that was invented some years ago to combat a guy who had a 350 hp chev and the only thing faster was his mouth.
I was only joking and didnt mean to target it at anybody.
Sure SS use it I regard you as a friend.
I mananged to get two Germans laughing at that one 5 minutes ago, translating from English to German, quite often the joke gets lost....this one worked!:lol:
After a bit, one guy asked me if racing a bucket was like "floging a dead horse"...... I think he took it too far!:girlfight:
craisin
27th March 2009, 22:51
sweet as SS ive been enjoying the tailend of summer riding on my big bad 50.
I get surprised how serious some big bike riders get as they race from redlight to redlight and i sail pass as they are still taking off :clap: I just think this bike is that slow the light will be green when i get there:clap:
craisin
27th March 2009, 22:57
sweet as SS ive been enjoying the tailend of summer riding on my big bad 50.
I get surprised how serious some big bike riders get as they race from redlight to redlight and i sail pass as they are still taking off :clap: I just think this bike is that slow the light will be green when i get there:clap:
bucketracer
28th March 2009, 19:55
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From:- http://www.smellofdeath.com/lloydy/piston_diag_guide.htm
Loydys Lambrettas Two Stroke Piston Diagnosis
PERFECT BROWN CROWN
The crown of this piston shows an ideal carbon pattern. The transfer ports of this two-stroke engine are flowing equally and the color of the carbon pattern is chocolate brown. That indicates that this engine's carb is jetted correctly.
FOUR-CORNER SEIZURE
This piston has vertical seizure marks at four equally spaced points around the circumference. A four-corner seizure is caused when the piston expands faster than the cylinder and the clearance between the piston and cylinder is reduced. Another common problem of this type is a single point seizure on the center of the exhaust side of the piston. However this occurs only on cylinders with bridged exhaust ports. The main causes for this problem are too quick warm-up, too lean carb jetting (main jet), or too hot of a spark plug range.
SHATTERED SKIRT
The skirts of this piston shattered because the piston to cylinder clearance was too great. When the piston is allowed to rattle in the cylinder bore, it develops stress cracks and eventually shatters.
SNAPPED ROD
The connecting rod of this engine snapped in half because the clearance between the rod and the thrust washers of the big end was too great. When the big end bearing wears out, the radial deflection of the rod becomes excessive and the rod suffers from torsion vibration. This leads to connecting rod breakage and catastrophic engine damage. The big end clearance should be checked every time you rebuild the top end. To check the side clearance of the connecting rod, insert a feeler gauge between the rod and a thrust washer. Check the maximum wear limits in your engine's factory service manual
Read the rest of it here:- http://www.smellofdeath.com/lloydy/piston_diag_guide.htm
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Chambers
28th March 2009, 20:05
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FOUR-CORNER SEIZURE
This piston has vertical seizure marks at four equally spaced points around the circumference. A four-corner seizure is caused when the piston expands faster than the cylinder and the clearance between the piston and cylinder is reduced. Another common problem of this type is a single point seizure on the center of the exhaust side of the piston. However this occurs only on cylinders with bridged exhaust ports. The main causes for this problem are too quick warm-up, too lean carb jetting (main jet), or too hot of a spark plug range.
Read the rest of it here:- http://www.smellofdeath.com/lloydy/piston_diag_guide.htm
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Didn't TZ have that problem at Taupo?
Interesting that 4 point seizure, and explination is from a Scooter shop too.
"The main causes for this problem are too quick warm-up, too lean carb jetting (main jet), or too hot of a spark plug range."
No mention of studs crushing the barrel.
TZ don't worry about those 8mm studs, just warm your bike up properly first before racing it! :msn-wink:
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bucketracer
28th March 2009, 21:25
Kreidler :- http://www.kreidler.nl fast air cooled 50cc 2-strokes.
Lots of interesting pictures of go fast Kreidler bits:- http://www.kreidler.nl/forum/viewtopic.php?t=23523
If you haven't got a PDF of Bells book by now your a lazy couch potatoe. :blink:
Another Graham Bell PDF:- http://www.kreidler.nl/artikelen/performance-tuning-graham-bell/performance-tuning-graham-bell.pdf
15Hp 50, check the graph http://www.kreidler.nl/forum/viewtopic.php?t=29410
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Skunk
28th March 2009, 21:44
Interesting that 4 point seizure, and explination is from a Scooter shop too.
"The main causes for this problem are too quick warm-up, too lean carb jetting (main jet), or too hot of a spark plug range."
No mention of studs crushing the barrel.
That's not their reason for 4 corner seizure, it's their reason for a SINGLE seizure point.
TZ350
28th March 2009, 22:03
From:- http://www.kartsport.org.nz/technical/engine_seizures.htm
Four corner seizure: Both sides of the piston will show heavy scoring and seizure marks on each side of the wrist pin hole. The pattern of these four seizure points often appears to be a perfect square, hence the slang term "four corner". The scoring takes place in this pattern because those areas of the piston casting are the thickest. When the piston is seriously overheated, the thick areas will expand and distort the most.
More piston death here:- http://www.kenoconnorracing.com/Piston%20Death.html
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SS90
29th March 2009, 00:20
From:- http://www.kartsport.org.nz/technical/engine_seizures.htm
Four corner seizure: Both sides of the piston will show heavy scoring and seizure marks on each side of the wrist pin hole. The pattern of these four seizure points often appears to be a perfect square, hence the slang term "four corner". The scoring takes place in this pattern because those areas of the piston casting are the thickest. When the piston is seriously overheated, the thick areas will expand and distort the most.
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And this is why pistons have "cam grind"..... "Modern" pistons (like the one Teezee uses) have a high silicone content (I think 8% from memory (as well as Nickel), and as such suffer much less from 4 point seizure problems than older pistons.
SS90
29th March 2009, 00:27
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From:- http://www.smellofdeath.com/lloydy/piston_diag_guide.htm
Loydys Lambrettas Two Stroke Piston Diagnosis
PERFECT BROWN CROWN
The crown of this piston shows an ideal carbon pattern. The transfer ports of this two-stroke engine are flowing equally and the color of the carbon pattern is chocolate brown. That indicates that this engine's carb is jetted correctly.
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Hahah, while I have to agree that the shape ("pattern") is quite good, I am unsure if the colour of the crown is "chocolate brown"....looks more like black (too rich) too me!..... :lol:
SS90
29th March 2009, 00:57
Didn't TZ have that problem at Taupo?
Interesting that 4 point seizure, and explination is from a Scooter shop too.
"The main causes for this problem are too quick warm-up, too lean carb jetting (main jet), or too hot of a spark plug range."
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Yes, not quite right there Chambers. As skunk pointed out, this article points out as to what happens.... (the piston expands too much) not as to what causes it.
The following paragraph starts........
"The main causes for this problem are too quick warm-up, too lean carb jetting (main jet), or too hot of a spark plug range."
This refers to the problem of a seizure mark on the piston opposite the exhaust bridge. (not 4 point seizure) In a water cooled bike, if you see this it is normally termed "cold seizure", and a result of not warming the engine up to Normal operating temp before thrashing it. But is also offers other reasons for the same problem. (wrong jetting, or too hot spark plug)
The last two reasons cause increased overall cylinder temperature, and as such increase the temperature of the exhaust port,(and exhaust port area of the piston crown) which is already a hot area (because of it's large port time area) due to the fact that with a bridge, you can safely exceed the 70% rule,as the bridge stops the ring protruding into the exhaust port at high R.P.M, a draw back of large exhaust port time areas is extreme localised heat around the piston crown on the exhaust side.
On a bridged exhaust, it the engine suffers heat related piston damage, it is normally on the exhaust side of the crown.
On a non bridged cylinder, heat related piston damaged normally shows it'self as a "holed" piston..... As because the exhaust port is much narrower (70% of the bore area or less) and simply not as hot as the wider bridged version. And as such, the centre of the piston seems to be the hottest point on these engines.
Personally, I have seen all these 3 things cause the same fault (in air cooled and water cooled engines)
Basically, the bridge is subject to great heat, and expands faster than the rest of the cylinder.
One way of combating this is to drill 2 small holes in the piston in line with the bridge, allowing a small amount of oil and fuel to lubricate the bridge.
Works quite well actually.
I recently saw a company in england who are trialling a new (well, not really new idea, but an application of the exhaust bridge hole concept) idea to combat the problem of 4 point seizure on their Lambretta Nicasil tuning cylinder.
Using the same concept, they have drilled 4 holes in the piston in line with the studs, again, the idea is, like the exhaust bridge, fuel an oil mixture cools those areas.
While I like the concept, even the guy who is testing it is not overly optimistic on it's success..... I am waiting to hear back from them after they have tested it.
Another note on the wasted stud.
When was the last time you saw a high performance water cooled 2 stroke cylinder with through studs?
Granted, having a cylinder that is retained to the cases via base plate allows for more room for exhaust size, (no studs in the way) (among other things), another advantage is that the cylinder is not "clamped" down, it is free too expand "vertically" as much as it wants, unhindered by stud expansion (or rather "lack of" stud expansion)....... Don't forget, the masters of air cooled performance (VW/Porsche) reduced the thickness of their studs as the engines where developed for more power.... I assure you the reason was not cost cutting!
I even know of some one who adapted a base plate system to his cylinder (at great expense) to solve this very problem... worked perfectly.......
TZ350
29th March 2009, 06:54
Another note on the wasted stud.
When was the last time you saw a high performance water cooled 2 stroke cylinder with through studs?
Good point that. Becouse the cylinder studs on a GP125 protrude above the barrel they make it hard to get the head of.
I am planning on fitting shorter studs and using the long aluminium head bolt/nuts from the early TZ's.
The benifits are:- the ends of the studs would not get in the way and the aluminium TZ bolt/nuts would act as locating dowels between the head and barrel and possibly their heat expansion will reduce the crush effect that SS90 talks about.
The good thing about using "o" rings as head gaskets is that you dont have to tighten the head nuts up much as you don't need a lot of clamping force to retain the head gasket, as the "o" ring is retained by its grove. You only need enough clamping force to stop the head rattling around and lifting of the barrel on the power stroke.
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SS90
29th March 2009, 09:36
G
The benifits are:- the ends of the studs would not get in the way and the aluminium TZ bolt/nuts would act as locating dowels between the head and barrel and possibly their heat expansion will reduce the crush effect that SS90 talks about.
The good thing about using "o" rings as head gaskets is that you dont have to tighten the head nuts up much as you don't need a lot of clamping force to retain the head gasket, as the "o" ring is retained by its grove. You only need enough clamping force to stop the head rattling around and lifting of the barrel on the power stroke.
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That's a really good idea..... I hadn't thought of that! :2thumbsup Do you think that Yamaha had that system for expansion, or for ease of access..... Maybe both?
TZ350
29th March 2009, 10:18
That's a really good idea..... I hadn't thought of that! :2thumbsup Do you think that Yamaha had that system for expansion, or for ease of access..... Maybe both?
Hard to say, the TZ is based on the RD road bike. The road bike cylinder head bolt/nuts were made of steel and clamped a copper head gasket and it is pretty easy to get the RD head out without studs sticking up like they do on the GP.
I guess whoever at Yamaha designed the race bits used "o" ring head gaskets and just copied the head bolt/nuts in aluminum.
Which could have been lucky.
When you think about it. The early air cooled Suzuki RM125's were base mount with no through studs and so are the TF100/125's that were/are popular bucket engines.
Picture of a aluminum TZ head bolt/nut.
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TZ350
29th March 2009, 11:04
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The Relationship Between Port Shape and Engine Performance for Two-Stroke Engines
Document Number: 1999-01-3333
Date Published: September 1999
Author(s):
Hisatoshi Kinoshita - Yamaha Motor Co., Ltd.
Yuh Motoyama - Yamaha Motor Co., Ltd.
Abstract: :eek: Measurement using a three-dimensional anemometric tester was made for the gas flow inside the cylinder of a two-stroke engine while the shape of the transfer port was modified. The relationship between port shape and engine performance was investigated for various factors that characterize the flow in cylinder. In this paper, we focused mainly on two engine running conditions: the maximum output at 11,750 rpm and the output at 10,000 rpm. As a result, we found that the maximum output is most related to the tangential inclination angles of the main transfer port and the inner vent radius of the main transfer duct.
This paper can be read/printed here:- http://www.2stroke-tuning.nl/media/pdfjes/porting.pdf
In case you missed it earlier. Here is a little bit of a gold mine:- http://www.2stroke-tuning.nl/media/
Port maps etc, some of its in German.
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I am not sure that this is everything SS90 has been talking about but it is good information.
I had to draw pictures and high light stuff to get my head around this.
Pic 1. As more power is developed, a hole/dip (Point B) appears in the the power curve just before max output (Point A).
The drivability of the bike is affected by this dip just before max power.
There is a trade off between power and drivability. (as we all know)
The main things that make more power, are, and in order of priority (1) the primary transfer tangental angle, (2) the inner transfer port radius, (3) the main transfer port axial inclination, (4) and main transfer port open size and shape. All high lighted in pic 2.
Pic 3 data from tests that show the trade off between power and drivability for the different variables.
Pic 4 configuration of the better test cylinders.
Get a copy of the paper from here:- http://www.2stroke-tuning.nl/media/pdfjes/porting.pdf
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TZ350
29th March 2009, 11:25
I will measure the port layout on my GP and a RM to see how they compair.
As SS90 says, now's the time to get a Dyno curve of my existing setup and then I can start development.
There is gold to be had in the transfer port shape and flow patterns. Not that I didn't already know that, just didnt know how to go about it and wisely left it alone but now I can see some direction to work towards.
When I get the motor apart I will look at unmasking the transfer ports in the way F5 suggests.
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SS90
29th March 2009, 12:34
I will measure the port layout on my GP and a RM to see how they compair.
As SS90 says, now's the time to get a Dyno curve of my existing setup and then I can start development.
There is gold to be had in the transfer port shape and flow patterns. Not that I didn't already know that, just didnt know how to go about it and wisely left it alone but now I can see some direction to work towards.
When I get the motor apart I will look at unmasking the transfer ports in the way F5 suggests.
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Yea, I am really keen too see what your power and torque curves look like.... I would expect that it would not look too dissimilar to the 1st graph you posted above...by that I mean, quite a "peaky curve". This is O.K, and if I am right, it will be a result the scavenge pattern, exhaust design and masked transfers.
If this is the case, and Teezee changes these points (O.K, granted, a new chamber might not be happening soon, but I believe that will be the nest thing.
If the transfers are masked, and the scavenge pattern is given the "new gereration" treatment.... even with the "old school chamber", I would expect not so much a massive peak horsepower gain, but I certainly would expect to see more torque (across the whole range), and a MUCH flatter, longer, power curve. My experience tells me that the latter is a result of unmasked transfers.
A good method is to put the piston in the cylinder, with the piston at what is effectively B.D.C...... so the transfers are completely uncovered (open), then, look at the "cutaway" in the skirt of the piston, in relation to the "cutaway" in the cylinder liner. As you have used a different piston, there is a good chance that the piston "cutaway" is higher than the liner. Just matching the piston to the liner "cutaway" would yield substantial gains in the characteristics of the power delivery.
I have seen 10% gains in horsepower AND Torque in more than one engine.
But yes, one step at a time, first a "benchmark" to base results on!
TZ350
29th March 2009, 13:46
If the transfers are masked, and the scavenge pattern is given the "new gereration" treatment.... even with the "old school chamber", I would expect not so much a massive peak horsepower gain, but I certainly would expect to see more torque (across the whole range), and a MUCH flatter, longer, power curve. My experience tells me that the latter is a result of unmasked transfers.
But yes, one step at a time, first a "benchmark" to base results on!
I can allready see a big difference between the GP's main transfer port axial (upwards) angle of 10 degrees and the new generation angles of 23-29 degrees. Speedpro recently made a new chamber and cylinder with the more upswept main transfers and he reports that it works well for him, flater longer and powerfull.
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Chambers
29th March 2009, 20:24
Check this baby out. The sales blurb says 100cc 30Hp 18,000rpm.
Whatever but you can bet its a hot little number and more than 20hp. 200Hp/Litre.
Look at that finning and how short the exhaust tract is.
Isn’t TZ banging on about shortening his GP's exhaust tract to reduce heat uptake into the cooling system and how it's important to have the roots of the fins as close to the combustion chamber as possible.
Might be onto something there.
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SS90
29th March 2009, 23:31
I can allready see a big difference between the GP's main transfer port axial (upwards) angle of 10 degrees and the new generation angles of 23-29 degrees. Speedpro recently made a new chamber and cylinder with the more upswept main transfers and he reports that it works well for him, flater longer and powerfull.
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Yes, I have to agree, those angles are pretty much where you would need to end up. A few years ago, while I was aware of concept, I didn't fully appreciate the gains that you would make with such slight changes.
One thing that you cylinder doesn't have, is "dividers" running up the centre of the transfer ports..... This (the divider) also forms part of the scavenge pattern system on more modern cylinders.
However, if you can somehow "rerofit" some sort of divider (even if it is only at the bridge of the transfers into the port, there will be gains there as well.
This enables a "curtain" effect from one stream to the other.
I am unsure if "Devcon" would be suitable for the environment, and obviously removing the liner, and either welding a divider into the aluminium skin, or welding a divider to the liner, then pressing it back in would be better.
However, as it is a "cast in" liner, that's not an option.
But I feel that some "thinking outside the box" would really help here!
SS90
30th March 2009, 00:00
Check this baby out. The sales blurb says 100cc 30Hp 18,000rpm.
Whatever but you can bet its a hot little number and more than 20hp. 200Hp/Litre.
Look at that finning and how short the exhaust tract is.
Isn’t TZ banging on about shortening his GP's exhaust tract to reduce heat uptake into the cooling system and how it's important to have the roots of the fins as close to the combustion chamber as possible.
Might be onto something there.
.
Here we touch on an interesting part of two stroke development!
To me, while I am unsure of the Manufacturer, it looks like a "fixed gear" Kart sport engine.
There are some anomolies with "fixed gear" Kart engines, and sadly, not all the tuning techniques that Kart sport use, are applicable to "geared" two stroke engines.
However, one comparison is "scooterMatic" (Twist and go).
As we are all aware, with an air cooled engine, you can't really SAFELY go lower that 1mm "squish", before you have problems with the piston touching the head.
However, because "fixed gear" Kart sport engines, and "scootermatics" do not have the demands placed on the power train that a geared engine does.
By that, I mean Kart sport engines and scootermatics are subject to "maximum R.P.M through most all of their operation.....where as a geared engine, the R.P.M goes from maximum, and then, when you change gear, it drops, say 4000 R.P.M, then when the gear is engaged, it goes back up again to maximum......there is alot of mechanical stress on the power train.
Like Teezee pointed out, there is up to .5mm stretch in the rod (he refers to "dynamic compression ratios"
On Kart sport and scootermatic engines, there is less mechanical stress on these parts (rod etc), therefore less stretch, and as such, the clearance is LESS variable.
As such, you can run "squish clearances" MUCH MUCH tighter than a Geared engine (0.5mm for example)
This, as we all know gives us the potential for more power.
While it is feasable to believe 100cc two stroke 30 P.S (I would like too see a curve or 2), if you attempted to put that power plant through a conventional gearbox, (also, let's not forget the amount of power that a gearbox "consumes"...... 30 Horsepower through no gearbox, but with a gearbox, I would say approx. 27 Horsepower would be realsistic) I surmise you would have a 25 gear close ratio "yo-yo"
Or, a scootermatic "constantly variable transmission"
As your "power band" on this engine would be the width of a mouses pubic hair!
The radial head is, in my opinion the best solution to displacing some heat, and it has been mentioned before (with reference to the last of the air cooled motocross bikes)
I think when Teezee talks of exhaust length, he refers to the distance from the cylinder liner, to the beginning of the the header, rather than having a header like the one in the picture........ Great for R.P.M, and stuff all else!
Becasuse, again, you CANNOT simply copy a Kart sport or scootermatic design concept (exhaust, scavenge pattern,compression,cylinder head design, EVEN PRIMARY COMPRESSION.... on Kart sport fixed gear engines, this is often higher than 1.5:1, as the engine is only operated at top R.P.M, and runs much higher compressions, so the "pumping losses" are reduced.)
The requirements of an engine (operating speeds,purpose, AND available gear ratios) are a big limiting factor in your set up (and therefore maximum power achieved)
That is why so many scootermatic (and Kart sport) tuners are able to get such high power results.
A point of interest, while the Kart sport and scootermatic boys get more power for the same engine capacity as motorcycle tuners (by default quite often), they always have very low torque results.... due to the fact that they run such big port time areas... the biggest "Thief" of torque (particularly in the lower R.P.M)
In my opinion, Kart sport and scootermatic tuners (not all, but most) base their concepts on "There is no substitute for R.P.M", and while this is clearly true, you can only get maximum benifit with this concept alone if you are not hindered by your available gear ratios, and carb size.... (like a 5 speed GP125 engine, with a 24mm carb!):laugh:
F5 Dave
30th March 2009, 16:45
Here you go TZ I was at the TeManawa show & came across this fine eastern block blaster with an oversized head & thought of you (aww) sadly my camera had got knocked onto a weird setting so excuse quality of pic.
While we are at it (bit of a sidetrack interlude) at it there was this piece of rolling history in somewhat of a sad state of repair but would still be pretty competitive today in 50 class & is current NZ 50cc record land speed holder (complete with bucket of parts, oh hilarious). . . .+ some other knock up, a replica of course, but 'the' replica.
speedpro
30th March 2009, 20:30
I am unsure if "Devcon" would be suitable for the environment,
Devcon seems to be made for this sort of effort. It does only last for about 1 dyno run in the exhaust port though. Been there etc etc . . . .
speedpro
30th March 2009, 20:38
While we are at it (bit of a sidetrack interlude) at it there was this piece of rolling history in somewhat of a sad state of repair but would still be pretty competitive today in 50 class & is current NZ 50cc record land speed holder (complete with bucket of parts, oh hilarious)
I've spent quite a bit of time chasing that #67 round various bucket tracks on my AC50. Me and Pete had many a good race, then same again when we both got F4s.
diesel pig
30th March 2009, 20:53
While we are at it (bit of a sidetrack interlude) at it there was this piece of rolling history in somewhat of a sad state of repair but would still be pretty competitive today in 50 class & is current NZ 50cc record land speed holder (complete with bucket of parts, oh hilarious)
So what exactly is this 80.21mph record holding machine?
speedpro
30th March 2009, 21:41
It started life as a Suzuki GT50 then Pete Sales bought it.
SS90
31st March 2009, 01:35
Hey Teezee,
While the subject of Expansion chambers can drive many people batty, I recall that you based your design on an Old 1970's RM125 design from Gordon Jennings..... And you used a header from (I think) a RG250?
Do you by chance have either a detailed series of pictures, or perhaps a diagram of your design that you can post?
fi5hy
31st March 2009, 07:25
Devcon .
If any one needs some I sell the Devcon titanium filler for $20 + gst
F5 Dave
31st March 2009, 08:34
Yeah GT50 water cooled with washing machine parts if I remember correctly. Just before he sold it it got some further work & got faster again then the next Pete bought it & we had some good races, then Regan bought it & he pedaled it ok too. . . . But there it has stayed along with the RD50 Pete built later for Tim & several other iconic bikes like Ziffle's Pepsi TF & Wheels hub centre front end Kawi & the GT125 with 2 MB50 top ends watercooled.:crybaby:
TZ350
31st March 2009, 16:27
Thomas recommends these books on Two Stroke Tuning.
(Some of these are PDF's that can be down loaded, read them then get yourself a copy of the book)
Graham Bell
http://www.kreidler.nl/artikelen/performance-tuning-graham-bell/performance-tuning-graham-bell.pdf
Gordon Jennings
http://www.vintagesleds.com/library/manuals/misc/Two-stroke%20Tuner's%20Handbook.pdf
http://toostroke.blogspot.com/2007/12/two-stroke-tuners-handbook.html
Engine Formulas
http://members.bellatlantic.net/~vze2p5sj/modelengines/engine1.htm
Reading Plugs.
http://www.dragstuff.com/techarticles/reading-spark-plugs.html
Rate of fuel burn and how it affects power output
http://www.factorypro.com/tech_tuning_procedures/tuning_fuel_octane_vs_power.html
Hey Teezee,
While the subject of Expansion chambers can drive many people batty, I recall that you based your design on an Old 1970's RM125 design from Gordon Jennings..... And you used a header from (I think) a RG250?
Do you by chance have either a detailed series of pictures, or perhaps a diagram of your design that you can post?
Thomas used the MOTA computer program to model and develop the Suzuki GP125
Using MOTA he settled on port timings of:-
Ex opens 86 ATDC, Trans opens 115 ATDC and inlet opens 145 BTDC / closes 55 ATDC for short tracks.
Ex opens 83 or 81 ATDC, Trans open 114 ATDC and inlet opens 145 BTDC / closes 85 ATDC for long tracks.
This was achieved by turning 1.75 and 1.5mm from the top of the barrels and lifting them up with spacers. The 1.75 long track barrel also had its port raised and widened to 70% of the bore.
Later when we were able to measure a RM125 we found Thomases work was very similar and was close to Bells specs for a RM125. We say we use Bells specs as an easy way to describe our port and pipe work..
For the RM125 pipe specs we used, see Fig 4.7 PDF Page 76, or Page 82 in the book..........
PDF of Graham Bell's Book. http://www.kreidler.nl/artikelen/performance-tuning-graham-bell/performance-tuning-graham-bell.pdf
RM125B General Hot-Up PDF Page 186-188, or Page 193-195 in the book..........
RM125C General Hot-Up PDF Page 200-202, or Page 208-210 in the book..........
RM125C Dyno test results PDF Page 171-172, or Page 178-179 in the book..........
PDF of Graham Bell's Book. http://www.kreidler.nl/artikelen/performance-tuning-graham-bell/performance-tuning-graham-bell.pdf
First pic is of the RG250 pipe, second pic is the cut-out front section we found we could use as it was very close to the RM specs.
Third pic is the RG/RM spec pipe, fourth pic shows where we cut the flange end off and turned it down in the lathe to fit the GP cylinder. Cutting it here made it easy to re-align the pipe to fit onto the GP.
Last pics are a comparison between the original RG pipe and the RM spec one. Thomas made the RM spec one in the original heavy gauge metal to better withstand the argy bargy of Bucket racing at Mt Wellington.
.
koba
31st March 2009, 19:45
Last pics are a comparison between the original RG pipe and the RM spec one. Thomas made the RM spec one in the original heavy gauge metal to better withstand the argy bargy of Bucket racing at Mt Wellington.
Hmm, not strictly on-topic but I notice the leathers in the background.
If those are the ones you were wearing at taupo I did notice you on the track.
I was on a 150 and noted your bike in my brain as VERY rapid in a straight line.
I think in staight line grunt it was probably in the top 3, the fastest didn't last long either.
This is all totally subjective and not really relevant but don't think all your efforts so far aren't working because it was punting along ok :niceone:
I can't remember if this was early (cooler motor) or not but It probably was either very early or very late in the races or warmup laps.
TZ350
31st March 2009, 20:33
Thanks Koba for noticing one of us, the bike and rider you saw was "Chambers" another rider in the ESE team with a bike built to the same specs.
.
SS90
1st April 2009, 06:09
Thomas used the MOTA computer program to model and develop the Suzuki GP125
Using MOTA he settled on port timings of:-
Ex opens 86 ATDC, Trans opens 115 ATDC and inlet opens 145 BTDC / closes 55 ATDC for short tracks.
Ex opens 83 or 81 ATDC, Trans open 114 ATDC and inlet opens 145 BTDC / closes 85 ATDC for long tracks.
This was achieved by turning 1.75 and 1.5mm from the top of the barrels and lifting them up with spacers. The 1.75 long track barrel also had its port raised and widened to 70% of the bore.
Later when we were able to measure a RM125 we found Thomases work was very similar and was close to Bells specs for a RM125. We say we use Bells specs as an easy way to describe our port and pipe work..
For the RM125 pipe specs we used, see Fig 4.7 PDF Page 76, or Page 82 in the book..........
PDF of Graham Bell's Book. http://www.kreidler.nl/artikelen/performance-tuning-graham-bell/performance-tuning-graham-bell.pdf
RM125B General Hot-Up PDF Page 186-188, or Page 193-195 in the book..........
RM125C General Hot-Up PDF Page 200-202, or Page 208-210 in the book..........
RM125C Dyno test results PDF Page 171-172, or Page 178-179 in the book..........
PDF of Graham Bell's Book. http://www.kreidler.nl/artikelen/performance-tuning-graham-bell/performance-tuning-graham-bell.pdf
First pic is of the RG250 pipe, second pic is the cut-out front section we found we could use as it was very close to the RM specs.
Third pic is the RG/RM spec pipe, fourth pic shows where we cut the flange end off and turned it down in the lathe to fit the GP cylinder. Cutting it here made it easy to re-align the pipe to fit onto the GP.
Last pics are a comparison between the original RG pipe and the RM spec one. Thomas made the RM spec one in the original heavy gauge metal to better withstand the argy bargy of Bucket racing at Mt Wellington.
.
Cool pipe!,
In all honesty, while it is quite dated in the design, it's not too bad... bit of "old, and "new" (of course it's hard to tell exactly from here, but comparing it to the RG pipe is a good reference!)
Just as a matter of curiousity..... if you get the opportunity (wife having a Tupperware evening and you banished to the shed, or something like that), could you measure the "tuned length".... Although it's fair to assume you have already done that though....
I would use the specs from the A G Bell book to get the length, but obviously you have made a few changes to that design!;)
I have been playing with a theoretical pipe design for your engine at work today, and would just like to compare it to what you have... I think it would be very interesting!
TZ350
1st April 2009, 07:11
I would use the specs from the A G Bell book to get the length, but obviously you have made a few changes to that design!;)
I have been playing with a theoretical pipe design for your engine at work today, and would just like to compare it to what you have... I think it would be very interesting!
Allthough Thomas used the RG front pipe, to get a good shape in the header section we followed the specs from Bells book carefully and all length measurements start from the piston and diameters are internal diameters. It should be close to Bells specs for a RM, close as we can get anyway.
.
SHELRACING
1st April 2009, 12:23
Hey TZ, just wondering. As you know I am experimenting. Chambers aside how much influence does the Tailpipe (muffler) have. Do different tailpipes affect the end results, in what way ?
Buckets4Me
1st April 2009, 18:39
Hey TZ, just wondering. As you know I am experimenting. Chambers aside how much influence does the Tailpipe (muffler) have. Do different tailpipes affect the end results, in what way ?
The last section of the expansion chamber, called the 'stinger', is in reality a bleed
pipe. Its function is to restrict gas flow out of the exhaust and create back pressure by
slowly bleeding off exhaust gas. This serves to assist the positive pulse wave in pushing
any spilled fuel/air charge back into the motor.
the stinger dimensions which I have found to be most
successful. You may find that a minor reduction in pipe diameter will raise the power
output, but do be careful. A stinger pipe smaller in diameter or longer than specified
could easily result in engine overheating and seizure. Therefore, I would suggest you
make only small changes and then thoroughly test the pipe before going any smaller.
Engine overheating, in its early stages, is indicated by the presence of oil burnt dark
brown under the piston crown. On the next stage the burnt oil turns black, until finally
'death ash' appears. After this, the piston can be holed at any time.
thank you Graham Bell
Skunk
1st April 2009, 20:30
Hey TZ, just wondering. As you know I am experimenting. Chambers aside how much influence does the Tailpipe (muffler) have. Do different tailpipes affect the end results, in what way ?
I do the stinger to the calculated dimensions and add the muffler on to the end of the stinger using an ID somewhat larger than the OD of the stinger.
TZ350
1st April 2009, 21:28
Now we realy truly know! The last word on ceramic coatings for the combustion chamber.
Abstract from:- http://www.sae.org/technical/papers/941911
The combustion chamber surface was coated with a 0.5-mm thickness of ceramic. Test results indicate that the thin ceramic-coated combustion chamber improves the part load to medium load operation considerably.
The performance of a conventional, carbureted, two-stroke spark-ignition (SI) engine can be improved by providing moderate thermal insulation in the combustion chamber. This will help to improve the vaporization characteristics in particular at part load and medium loads.
But it affects the performance at higher speeds and at higher loads to the extent of knock and loss of brake power by about 18%.
So now we know for sure, ceramic coating does not work for high performance 2-stroke race engines running on petrol.
.
SS90
2nd April 2009, 04:34
The last section of the expansion chamber, called the 'stinger', is in reality a bleed
pipe. Its function is to restrict gas flow out of the exhaust and create back pressure by
slowly bleeding off exhaust gas. This serves to assist the positive pulse wave in pushing
any spilled fuel/air charge back into the motor.
the stinger dimensions which I have found to be most
successful. You may find that a minor reduction in pipe diameter will raise the power
output, but do be careful. A stinger pipe smaller in diameter or longer than specified
could easily result in engine overheating and seizure. Therefore, I would suggest you
make only small changes and then thoroughly test the pipe before going any smaller.
Engine overheating, in its early stages, is indicated by the presence of oil burnt dark
brown under the piston crown. On the next stage the burnt oil turns black, until finally
'death ash' appears. After this, the piston can be holed at any time.
thank you Graham Bell
I think that Shellracing was questioning the Muffler system, and it's effect on power, opposed to the "stinger" section of the chamber...while the two are related, Have you found anything in Bells book on Mufflers, and their effect on power?;)
Buckets4Me
2nd April 2009, 06:00
I think that Shellracing was questioning the Muffler system, and it's effect on power, opposed to the "stinger" section of the chamber...while the two are related, Have you found anything in Bells book on Mufflers, and their effect on power?;)
did Bell have a problem with noise ?????
or buraRats and neibours ?????
:scooter: them where the days Ay Tz no 98db limit for the TZ350 back then
Pudding
2nd April 2009, 10:52
Abstract from:- http://www.sae.org/technical/papers/941911
"The combustion chamber surface was coated with a 0.5-mm thickness of ceramic. Test results show it affects the performance at higher speeds and at higher loads to the extent of knock and loss of brake power by about 18%. "
So now we know for sure, ceramic coating does not work for high performance 2-stroke race engines.
.
You guys are pretty smart, figuring out ceramic won't work and then later finding an SAE paper that proves you were right. Good on you :2thumbsup clever bastards, tell Thomas I think he is good looking . :love: I just love brains.
F5 Dave
2nd April 2009, 11:05
Well he did say 'tailpipe (muffler)' so was combining the issue.
You can use the muffler as the stinger is space is restricted, but important to repack muffler, which should do regularly anyway as will create turbulence.
Often neglected is the baffle section if very steep will increase piston temp as well.
As always the interrelationship is a compromise & nothing should considered in isolation.
SHELRACING
2nd April 2009, 12:34
Thanks SS90 / F5. I was referring to the Muffler rather than the stinger but all information is usefull, will repack my muffler anyway.
Another question then (probably obvious to some). What's the difference between 2 stroke and 4 stroke packing, as you may have guessed I have four stroke packing that worked well on a Pit bike type muffler, can I use it on the 2 stroke ??
Cheers Steve
Hey Sorry I may have dragged you a bit off topic TZ
TZ350
2nd April 2009, 18:40
Hey Sorry I may have dragged you a bit off topic TZ
Its all good. Its interesting what others are working on, we all learn from it, and the suggestions others make. :niceone:
.
craisin
2nd April 2009, 19:50
Thanks SS90 / F5. I was referring to the Muffler rather than the stinger but all information is usefull, will repack my muffler anyway.
Another question then (probably obvious to some). What's the difference between 2 stroke and 4 stroke packing, as you may have guessed I have four stroke packing that worked well on a Pit bike type muffler, can I use it on the 2 stroke ??
Cheers Steve
Hey Sorry I may have dragged you a bit off topic TZ
hey Ive still got the muffler that was on the RM when I first got it Steve it came off that chamber that had been altered at the front to suit the TS250 motor that was on it when I was given it.
I was going to put it on the four stroke.
you can have it if you want
craisin
3rd April 2009, 03:13
sorry a mate came round i will PM you say hello to nana for me
bucketracer
3rd April 2009, 21:49
Inspired by TZ350 I have been looking over SAE papers,
...............and Whats This!!!!
"The drop in delivery ratio caused by increasing the crankcase volume can be fairly well compensated for by tuning the exhaust and inlet systems. "
from SAE Paper:- http://www.sae.org/technical/papers/670030
didn't Speedpro say this earlier? :blink:
.
SS90
4th April 2009, 05:43
No, I did, in one of my first posts.:whistle:
I also went on to explain that there was advantages in having a ratio of 1.5:1, but no real gains over that.
It all goes back to the days when, due to production costs, (and piddly little cranks) most machines where about 1.3:1, and increasing that brought gains...... it seems the concept just got stuck in peoples minds, and they always took that approach.
That's when Teezee measured his, and found it was something like 1.33:1
So it looks like he could get some tangeable gains with increasing to something closer to 1.5:1, but of course,he (and most people are now aware) that it's not just a matter of "increasing and decreasing", you have to know what you have, and, what you should end up with.
Think of this....Lower/raise your primary compression...SURE! to what value?
We always measure our cylinder compression (don't we?), no-one in their right mind would alter cylinder compression with-out measuring 1) what they have now, and 2) working out what they want it to be!
The same is true of primary compression.
Although, mistakes with crankcase volumes are far less catastrophic than cylinder compression ratios!
I think it was the Yamaha race engineer Fujio Nagaio that did all the work for us in regards to maximum values.
He probably wrote the paper you read....the quote you used are his exact words!
It's not just a matter of "lowering (or raising) the primary compression" if you want to make a fast two stroke, you have to apply values to each modification you make. Remember that the power stroke on a two stroke engine as bloody feeble (at best), and the difference between a fast two stroke and a slow two stroke is the STRENGTH of it's power stroke. (this is why two stroke engines make such big gains with cylinder compression) In my opinion, Tuning a two stroke well is when you pay attention to this concept.
Don't forget that, because of the limitations placed on 2 stroke 125cc bikes in Bucket racing, Teezee will never have "a properly tuned intake"...... the carb is too small, and as such, his engine will see quite big gains from getting the primary compression ratio to as close to 1.5:1 as possable!
I can't help but think that we are all waiting for Teezee's first dyno runs on the current set up, then compared to his planned mods he posted a week back.... I know I am!
TZ350
4th April 2009, 06:52
.
Increasing the primary compression ratio to 1.5:1 or as close as, along with improvements to the transfer window (improvement hopefully) is very near the top of my to do list.
Picture-1 is what the piston looks like in the transfer window at BDC. Picture-2 is the underside of the piston. Picture-3 is the topside of the piston. Not very coloured on the underside, and I wonder if I can lean it out a bit more? but it sure looks like its hot on top, I don't understand it? maybe the oil?.
Hopefully get the bike onto a dyno tomorow. Its a home made one and used by a lot of Bucketers. The Guy who runs it sure knows what he is up to but I understand printing graphs is an issue and I will have to take a photo of the computer screen. heres hoping I can get a base line graph to start work from.
.
TZ350
4th April 2009, 20:42
Abstract:from http://www.sae.org/technical/papers/690136
"In order to increase the air charge of crankcase-scavenged 2-stroke-cycle engines, the relations between delivery ratio and engine speed were investigated on a rotary disc-valve inlet port engine and on a conventional piston-valve inlet port engine by varying through wide limits the angle area and timing of the inlet port.
For the inlet port configuration tested on the first engine, it was found that there was an optimum cut angle of the rotary disc valve, which produced a certain angle area. To improve the delivery ratio characteristics at a given speed, it was not necessary to change this angle area; it was effective to change only the timing of the inlet port by shifting the disc valve around the crankshaft.
For the piston-valve inlet port engine, the results showed that a wide, low port, which was also found to have a higher flow coefficient, produced a higher delivery ratio over the entire engine speed range than a narrow, high port. For the configuration tested (with no inlet or exhaust pipes), the maximum delivery ratio of the wide, low port was nearly in proportion to the effective crankcase stroke"...................................
(1) Interesting, that there was an optimum cut angle of the rotary disc valve, which produced a certain angle area. To improve the delivery ratio characteristics at a given speed, it was not necessary to change this angle area; it was effective to change only the timing of the inlet port by shifting the disc valve around the crankshaft.
(2) And for piston valve inlets, that a wide, low port, which was also found to have a higher flow coefficient, produced a higher delivery ratio over the entire engine speed range than a narrow, high port.
.
speedpro
4th April 2009, 21:30
(2) And for piston valve inlets, that a wide, low port, which was also found to have a higher flow coefficient, produced a higher delivery ratio over the entire engine speed range than a narrow, high port.
.
The only trouble with achieving this is that on the motors we use such as TS100/125ERs for instance, if we move the port floor so that we get the timing we need then we get to a narrow part of the barrel which limits how wide the port can be made. In fact the lower part of the port has to be narrowed so you end up with a "T" shaped inlet port with a bridge down the middle. Because it's narrow at the bottom by necessity you need to keep a bit of height to get the area. I see why it would work though - you end up with the port timing required for good resonance and a reasonable port cross-section for velocity. Having said that you can with a bit of careful work end up with a pretty good piston port on a TS100 motor.
SS90
4th April 2009, 23:10
.
Increasing the primary compression ratio to 1.5:1 or as close as, along with improvements to the transfer window (improvement hopefully) is very near the top of my to do list.
Picture-1 is what the piston looks like in the transfer window at BDC. Picture-2 is the underside of the piston. Picture-3 is the topside of the piston. Not very coloured on the underside, and I wonder if I can lean it out a bit more? but it sure looks like its hot on top, I don't understand it? maybe the oil?.
Hopefully get the bike onto a dyno tomorow. Its a home made one and used by a lot of Bucketers. The Guy who runs it sure knows what he is up to but I understand printing graphs is an issue and I will have to take a photo of the computer screen. heres hoping I can get a base line graph to start work from.
.
Hmmm,
Damn! I see the problem with the piston "shouding" the available transfer area, and I suspected as much, it's something I had to deal with before.
Somewhere at work I have a piston that I modified (with success) for just such a problem, I'll go there after lunch and see if I can find it.
It is (of course) dangerous to modify this part of the piston too much, as it weakens the skirt area, but obviously a little helps alot!
I know a few aftermarket manufacturers who make special pistons for just such an occasion, with webs cast inside the skirt to strengthen it. I'll have a look for those too.
TZ350
5th April 2009, 00:13
Thanks...Any ideas and pictures on unmasking the transfers would be helpfull.
I have run into problems before by cutting the skirt to unmask the transfer.
The problem with the GP is that its transfers are arranged on an angle, unlike most bikes that have the transfer windows square across the motor. Which means that pistons from other motors have to have their transfer windows cut back a long way.
On the pistons I have cutting the skirt, cuts away some bracing cast into the piston and the pistons are prone to cracking.
Wiesco pistons have a thicker forged skirt that might be more usefull and I am trying to get one the right size, 56mm with 16mm pin (1988-1990 KX125).
.
SS90
5th April 2009, 03:52
O.k
I can't find the piston I am looking for, and will have to wait for the boy to come on Monday.
Yea, I know, my fault, but it's nice to have a scapegoat when you can't find things!:shifty:
However, I "feel your pain" in regards to cracked pistons when you relieve that area, I wrecked a few in my time for that very reason!:doh:
I have attached a picture of a polini 133cc piston, as an example of what "appears" to be the maximum you can safely go on a piston before it gets dangerous.
Looking at other manufacturers, no-one I have seen has exceeded that shape, and with my experience (and yours), that seems as it is for good reason!
But I had a thought today, when thinking of the problem.
I have to cut an intake window into the skirt of my pistons, which weakens the skirt in that area (of course), but if I don't modify the piston in any other way, all is well.... But..... if I cut the transfer cutaway in the piston further up, (to unshroud the transfers, which is a problem when I use a spacer under the cylinder when I "stroke" the engines... (I don't need a spacer unless I do, so it is unshrouded nicely otherwise)) it would always crack between the intake window and the higher transfer cutaway (if I increased the transfer cutaway in the piston too much that is),
I suspect in a similar way to yours.......
What do you think to the idea of instead of taking lots of material out from the piston to unshroud the transfer (which you know you cannot do), just drill a series of small "bleed" holes in the skirt in the area you want to remove.... (or perhaps 2 larger ones)? Which would not compromise the integrity of the skirt as much as simply removing material!
The holes, can simply "bleed" fuel air mixture into the cylinder transfers at B.D.C (a little bit like the Mallossi system, which it'self is a copy of an old Royal Enfield design from the 1920's) but instead of above the gudgeon pin, it only "bleeds" below the pin, (which is otherwise unused)..... and of course you don't need to put holes on the cylinder to facilitate this, as you have a spacer, there is an increase in transfer port area, equal to the height of the spacer....
I am unsure how much effect just drilling the holes will have, (compared to the power gains (particularly Torque) you would make by completely removing the "offending" piston skirt area), but, from personal experience, unshrouding this area just a small amount brings huge gains.
I am sure you agree, currently you are essentially trying to "post an elephant through a mailbox" when you compare the available area (cylinder liner cutaway), to the piston transfer cutaway.....
Anyway, simply removing the piston skirt in this area just causes failures anyway!
While holes in the skirt don't completely remove the problem, even a 30% gain in transfer area yields surprisingly high results....
Personally, I have never seen this done (the hole concept in this area), so it is only theory, but Science does back this theory...... so I feel it has merit!
The Polini pictures I have attached are commonly "spaced up" 5mm under the cylinder when tuning, and you only have to increase the "transfer cutaway" a small amount when doing so, as the manufacturers have thought of this when designing the piston...... I have never personally seen a failure on these pistons... they are however very heavily engineered in the thickness of the skirt walls....
The 4th picture is of a modified 136cc Mallossi cylinder (I can't find a picture with the piston in, sorry, but I assure you that the piston cutaway is matched perfectly to the cylinder at B.D.C) it has the C.V.F system, as you can see by the "extra transfer ports"
It has the "reed valve piston window induction" conversion fitted, and I used an aftermarket stronger piston.....
You will notice that the transfer area has been "relieved", and it is NOT SYMMETRICAL... this is because when I relieve the piston cutaway, I leave more material on the intake window side....as this is a weak point on all "piston window induction" cylinders..... However, this is an old engine I did years ago, and I have since changed my cut out design on the Mallossi conversions I do, and can now fully "open" the cylinder transfer cutaways (on the piston as well)
This particular engine was 17 P.S (with a 28mm carb).....to get over 20 P.S...... these cylinders start to look "a little different" (to say the least!)
The last picture is of an original Malossi 136cc cylinder.... you can see how much material you have to remove... even with the C.V.F system.... gains are still made in this area!
Of course, on my aluminium cyliders, it all looks different again.........:msn-wink:
If you don't feel that the "bleed hole" concept is benificial......you could always grind a series of "boost ports" into the cylinder wall (fed via small holes in the piston skirt, just below the ring groove, just as Aeromachi did in the late 70's)..... If done correctly, this will certainly scavenge the area under the piston much more.......I have done this a few times myself (on older styled engines), and the gains have been fantastic.... I am doing one this week at work, and if you like I could post a few pictures as the process pans out...
Remember the piston you are using has such small cutaways, because it is designed to be used in a cylinder that has boost ports, negating the need for large transfer cutaways in the piston, as the boost ports utilise that Fuel/air mixture!
TZ350
5th April 2009, 08:21
I am doing one this week at work, and if you like I could post a few pictures as the process pans out...
Remember the piston you are using has such small cutaways, because it is designed to be used in a cylinder that has boost ports, negating the need for large transfer cutaways in the piston, as the boost ports utilise that Fuel/air mixture!
Thanks for the info I will look at it carefully. I would be pleased to see the progress. I had allways wondered about the small cutouts and not thought about the re-direction to the boost ports.
I am off to the dyno this morning, hopefully get some useable data. I have several bikes to test, all setup slightly differently with respect to port timing and chambers.
.
Buckets4Me
5th April 2009, 18:02
:bleh::niceone::msn-wink::clap::first:
:Pokey::drool:
TZ350
5th April 2009, 19:17
While we are still on pistons. I photographed these ones at Johns shed.
1st pic is of a Honda RS125 piston showing a polished area around the squish band. 2nd pic is the RS piston at the BDC pisition in a RM Barrel. 4th pic is why you don't use a different brand of oil in your RS just because its cheaper, sold by a friend, sponsored by your local dealer, Etc., Etc., stick with what is known to work.
.
Buckets4Me
5th April 2009, 19:29
While we are still on pistons. I photographed these ones at Johns shed.
.
what where you doing at Johns one wonders :whistle:
TZ350
5th April 2009, 19:43
what where you doing at Johns one wonders :whistle:
Ok. I was at Johns to dyno the bikes and yours turned out to be the best!!!! OK. :angry2: and mine was the worst. :crybaby:
All four bikes were run up and it turned out that the more Hotted-Up they were the worse they performed. :pinch:
The best one (yours) is running a RG250 pipe and has 1.75mm turned from the top of the barrel and "o" ringed, with no other mods. Real simple and ran the best on the initial tests, it also confirmed what we have seen on the track.
As the testing went on there were a few more surprises. I need to draw some graphs from the data, then I can post a report. Speedpro turned up, :Oops: so now I can't gloss the results. :eek5:
John and Carl working the dyno, Bikes:- Buckets4me's RS/GP125, Chambers GP125, Nedkellys RS/GP125 and TZ350's No 14.
Many thanks to John for his time and help.
.
TZ350
5th April 2009, 20:38
What do you think to the idea of instead of taking lots of material out from the piston to unshroud the transfer (which you know you cannot do), just drill a series of small "bleed" holes in the skirt in the area you want to remove.... (or perhaps 2 larger ones)? Which would not compromise the integrity of the skirt as much as simply removing material! The holes, can simply "bleed" fuel air mixture into the cylinder transfers at B.D.C
I am unsure how much effect just drilling the holes will have, (compared to the power gains (particularly Torque) you would make by completely removing the "offending" piston skirt area), but, from personal experience, unshrouding this area just a small amount brings huge gains.
I am sure you agree, currently you are essentially trying to "post an elephant through a mailbox" when you compare the available area (cylinder liner cutaway), to the piston transfer cutaway.....
While holes in the skirt don't completely remove the problem, even a 30% gain in transfer area yields surprisingly high results....
Trying to "post an elephant through a mailbox" I like that. Yes I think this is a very worthwhile area to seriously look at. Thanks for your help.
I saw on the dyno today after we got the bike dialed in, the graphed results of my old school porting compaired to the new generation approch and can see why you know its the way we should go.
Both graphs peaked about 19.5 Rw-Hp but the other bike with the new generation ports had a much longer flater higher torque curve.
.
SS90
5th April 2009, 23:12
I saw on the dyno today after we got the bike dialed in, the graphed results of my old school porting compaired to the new generation approch and can see why you know its the way we should go.
Both graphs peaked about 19.5 Rw-Hp but the other bike with the new generation ports had a much longer flater higher torque curve.
.
Yea, I thought that would be the case..... While, of course the HP results should always be considered a little abstract, I can assure you that as long as the conditions are the same the next time you do some runs, (after mods) the results will be comparable.....home made dyno's get a bad reputations (un deserved actually), as the only real difference between inertia dyno's is the software used for corrrection factors.... most home made dyno's don't even use correction factors for each run, so if it (the dyno) is at roughly the same atmospheric pressure, and altitude, the results are always reliable)
Well, as far as consistency goes anyway!
It regards to the boost port concept, I have included an attachment from an old piston port cylinder (Vespa big frame) from the early 60's.
I simply ground 2 "channels" into the back wall of the cylinder, with the top of the channels about 1mm higher than the transfers. I didn't take a photo of the piston on this job (I don't know why I didn't !, but I am doing another one this week, so photograph that one).
Just below the ring groove I drill two 6mm holes (that line up with the cylinder grooves), and at B.D.C, the piston crown uncovers the top edge of the grooves and fuel from under the piston feeds through the 2 holes, up the grooves, and into the combustion chamber.....
A set of "low tech" boost ports!
This system works very well on the older style engines,That, because of design faults had badly shrouded transfers anyway, but I modify the transfers HEAVILY, (extra spiggot windows (in the liner and piston) and get gains there, but with the "boost port" system, these gains are increased somewhat more.
Of course, this "system" is fed via fuel from under the piston ("scavenged"), where as most modern boost port systems feed straight from either the crankcase, or in the case of a reed valve, straight from the inlet manifold into the combustion chamber, or, sometimes from the reed block straight into the transfer ports, as well as the combustion chamber, and the fuel under the piston is not so important, as it is well compensated for by the inlet manifold fed boost ports......
F5 Dave
6th April 2009, 12:13
Having just reacquainted myself with a GP cylinder; the Briggs & Stratton type transfer port (as you say low tech boostport is a simple groove) is actually already std in the back of the barrel. I've never seen this in a Jap engine before. It would be interesting to find out the development process the GP went through to be so different to it's their designs.
TZ350
6th April 2009, 18:56
TZ's Dyno Report. Rear wheel HP curve charted against road speed (Kmh), very handy for setting up the gearing.
Before we ran the bike up, John told me that most bikes that have been tuned on the track are usualy over advanced and over rich.
We warmed the bike up and it sounded sharp and loud, but the exhaust fumes were something else, they were eye watering.
The bike sounded sharp and I had high hopes. The good 4-strokes at Mt Wellington are pushing 18-20 RW-HP.
Run 1 returned 15.8hp at 78Kmh, curve-1. Well :( not a happy camper.
Over the next few runs the ignition was retarded a bit at a time untill we ran out of adjustment. The ignition was retarded from 20 degrees BTDC to about 15 and with each step the power went up, the eyewatering fumes went away and the sharp exhaust note softened and became mellow.
Then we started leaning the main jet out, going from 117.5 to 105 a step at a time. With each change the power improved. Even changing the needle clip one notch showed up on the dyno. We stoped when adjustments started making little difference.
The last run curve-2 returned 19.5 RW-HP peaking at 84Kmh. Just right for Mt Wellington. The runs were done in batches of five, John pointed out that the bike went better as it got hot and interpreted this to mean that the tuned length of the pipe was a little to longe for the state of tune of the exhaust port. That is probably right as the RM125 spec pipe was originaly intended for an exhaust opening 86 degrees ATDC and we were running an exhaust which was opening at 81 degrees ATDC.
Typical temperatures taken during a hard run were. Head-57, Barrel-98, Header-250, Pipe Midsection-170 degrees C.
The last thing John showed me was my last 19.5 RW-HP run compared to engines that have had the modern porting treatment, curves-3 and 4. The features are my old school graph was very good in an old school way and initialy had better torque curve but the modern porting gave no more Hp and it had an initial a steeper start but a much longer power band. The modern curve looks very much like the curves in the SAE paper posted earlier.
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SS90
6th April 2009, 19:25
Curve #2 looks the best to me....... big long power curve, and obviously the torque curve would be longer than all the others as well.....
Cool!
SS90
6th April 2009, 19:27
Having just reacquainted myself with a GP cylinder; the Briggs & Stratton type transfer port (as you say low tech boostport is a simple groove) is actually already std in the back of the barrel. I've never seen this in a Jap engine before. It would be interesting to find out the development process the GP went through to be so different to it's their designs.
It was Aeromachi that pioneered that design, and yea, it seems to work.... I am quite surprised that the GP has it, like you, I have never seen a Jamanese engine with one.....and looking back at a early picture of Teezee's piston, there could be a gain in drilling a hole higher up the piston (above the existing one)
Actually, no, I looked again, and the hole is high enough...... the only gains you would make would be in the angle that the boost port enters the cylinder.......55 Deg (maybe) would be an angle to consider.......
Now that you are making almost 5 PS more...... I can't help but wonder what you will gain with the changes you have outlined previously.....
Experience tells me that you are unlikely to make more peak power, but rather with the things we have talked about you will increase "the width of your power band" quite dramatically, as well as increasing the low RPM torque......
I keep thinking back to the idea of holes in the skirt to increase the relief area now.......
TZ350
6th April 2009, 19:41
Barrel Pic's.
Pic's 3 & 4 show an early 70's TM barrel with the traditional "Two" transfers.
Pic's 1 & 2 show a brand new late 70's GP125 barrel with rear gully port and two secondry ports.
The GP's secondrys look like after thoughts when you look at the ugly way they have been siamesed into the main transfer port ducts, pic-2.
I was thinking of opening these up and adding dividers between the mains and secondrys.
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TZ350
6th April 2009, 20:04
Now that you are making almost 5 PS more...... I can't help but wonder what you will gain with the changes you have outlined previously.....
Experience tells me that you are unlikely to make more peak power, but rather with the things we have talked about you will increase "the width of your power band" quite dramatically, as well as increasing the low RPM torque......
I keep thinking back to the idea of holes in the skirt to increase the relief area now.......
Yes 5 PS for just retarding the ignition and leaning it out a bit.
Like you I don't expect any/much more Hp but I am excited by the possibilitys of a wider power band. Thanks for your help with this.
I am going to have to formulate an action plan. One of the problems I have is working out how to get a main port that is angled up at 10 degrees to 25-30 degrees. I can't just file away at the port, it still has to retain its timing.
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SS90
6th April 2009, 20:07
Hoho!
O.K, I see what you mean..... I believe that because of the "crowded" design, you must be careful that the streams don't "short circuit". That said, changing the angles of the secondaries will be of HUGE gain on this design.
Personally, I would treat the secondary transfers ports like boost ports (as far as their angles are concerned., particularly in relation to the angle they point to the combustion chamber... and have them enter at quite a high angle into the cylinder.... possibly the same angle as the rear boost port (which I would possibly raise to 55 deg...). have them work in symmetry......
Not 100% sure on the angles, some experimenting is needed.
The whole design really is a compromise though..... I am confident there is real gains scavenging what is left under the piston, especially from what I see of the port set up......
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