ESE's works engine tuner

[2T Institute]

Andy rang me and asked about a few jetting changes, sounds to have worked OK.
He seems to like " hanging on for grim death " in a straight line, as he calls it, but now it wheelstands off every turn.
Fuck I wish I could ride it, maybe bolt me on the back one day, like they did with the BSL500, and did 280 clicks at Puke to see if my daks turned brown.
My face was white and my knuckles were blue, but the seat was still green, just.

Why not just bolt 4 roller blades on to the chair and tie a ski rope onto the grab rail? :eek: just make sure the rider doesn't put you into a whip though:lol:

[Bert]

Well I must say you got it right with the 400. Was at manfield yesterday and man that thing is cool. It was flying at the end of the day. Smelt good sounded amazing and went like a f*cken rocket all day. Lots of people wanting one at the end of the day. Me included. weapon. I might have some video but I think I forgot to turn on the sound. bugger.


Andy rang me and asked about a few jetting changes, sounds to have worked OK.
He seems to like " hanging on for grim death " in a straight line, as he calls it, but now it wheelstands off every turn.
Fuck I wish I could ride it, maybe bolt me on the back one day, like they did with the BSL500, and did 280 clicks at Puke to see if my daks turned brown.
My face was white and my knuckles were blue, but the seat was still green, just.

I take my hat off to you Sir Wobs. As rich said it looked & sounded f##ken amazing yesterday. When I saw the bricky he had the biggest grin (was excited as a 16 year old boy in a strip bar)...

[husaberg]

1995 nx4.........

[husaberg]

2003 NX4
I will follow up with a litle something else once i convince my camera to talk to my computer:msn-wink:

These are off Ebay .In pic three you can see the strp in the EX although not so clear because of carbon

[wobbly]

Yea well Lozza, why the fuck do you think im a wheelchair, doin exactly that shit is exactly why.
But yes it is cool when others appreciate the effort and sweat that went into the 400.
The Bricky paid good money - he has already had a heap of fun on it, what more could a guy ask for from a toy.
His wife says is the best thing that has happened to him , apart from the kids, and they are debating that now.

[husaberg]

Yea well Lozza, why the fuck do you think im a wheelchair, doin exactly that shit is exactly why.
But yes it is cool when others appreciate the effort and sweat that went into the 400.
The Bricky paid good money - he has already had a heap of fun on it, what more could a guy ask for from a toy.
His wife says is the best thing that has happened to him , apart from the kids, and they are debating that now.

Wob i was looking at one of Mikes video's and came across the NS400 with the CR125 top end was it finished looked kind of neat in the RGV frame.

http://www.youtube.com/watch?v=3oiMTcBLO7M


I always kind of thought the NS400 was a little underrated.

http://www.ns400r.de/pictures/engine.jpg
Shame they arn't Crankcase reed.
Photo of the cabbage tree in the House paddock.thought it might have blown down by now. Sorry its fuzzy taken from my cell.

[Forgi]

Hi Everyone!

I'm Balazs from Hungary. Dear Fritz, and Jan nice to see you both of you here as well!

Well, I have read the comments til this moment, but now I'd like to ask some questions.

I have been studying the work of the exhaust nozzle for a long time, so I'm very glad that Wobbly wrote about it in details.

Wobbly!

Is it possible that the cause of the '75% rule' is that after the opening of the exhaust port the positive preassure in the exhaust port/duct lasts until 55-60 degrees, and then the diffusor starts to work, so the suction will be determinative? This area of the exhaust port at 55-60 degrees is the same as the exhaust duct's area should be (cc 75%).

If the presumption is right the exhaust port's lower edge doesn't have to be at ATDC 180 degrees, it would be enough at 135-145 degrees. In this case the proportion of the effective exhaust port area and the exhaust duct area would be 1:1. Of course the shape of the port is not the same and there is some important factors as well, but in general the abovementioned are right, aren't they?

By the way what is your opinion, where the exhaust nozzle has to be, how far from the exhaust port? And what about the exhaust duct? It has to narrow gradually all along, or is it ok, if it is 1:1 and only on the last 10-20 mm narrow to 75%.

TeeZee!

Have you tested this nozzle? About a year ago I read that it was planed to make it, but I haven't seen dyno test about it.

[TZ350]

... the exhaust port's lower edge doesn't have to be at 180 degrees ATDC ...

Hi Balazs, I remember seeing a post some place where Jan talked about getting more power (reduced short circuiting) from razing the exhaust port floor. Your idea makes sence to me, hopefully Wobbly will be able to tell us more.


TeeZee!

Have you tested this nozzle? About a year ago I read that it was planed to make it, but I haven't seen dyno test about it.

No ... reliability issues have kept me busy, and now I am building a completely new lighter bike. I am planning two engine setups for it, one will be a water cooled 100 with CVT transmission and that will have an exhaust nozzle.

[wobbly]

The idea of reducing the duct volume was pushed along by Jan at Aprilia where they CNC cut the shape.
He lifted the floor, but more importantly the bottom corner radius was increased, this also reduced the volume, and helped reduce short circuiting from the A port.
With the cosine of the 25* down angle taken into consideration, I would guess the area at the port exit was quite small in the cylinder.
I have found that the 75% rule work OK, as does making the duct exit area the same as the main port area only ( often works out to be the same value ) but that the exit area must include
the 1/2 moon cutouts, or be very oval shaped, depending upon 3 port or T port.
I dont know how far you could take this idea, I did think of having a Honda type powervalve plate in the floor of the duct, that lifted up, to reduce the area
outside the port, and could be servo driven,along with - or independent, of the main valve.
Changing the volume affects the HelmHoltz frequency, as does changing the length, but what is the optimum - only testing different lengths, and adjusting the pipe accordingly
would find out.
As it stands, the nozzle being part of the flange is all we can do with an existing cylinder.
Welding up the last part of the duct works OK, but I always try and get as far up into the duct as I can to reduce the vertical height gradually, and widen it to get the Aux ducts to flow better.

The NS400 is hiding in a corner somewhere 1/2 finished, Jarred has financial issues that have taken a long time to resolve.

[2T Institute]

Yea well Lozza, why the fuck do you think im a wheelchair, doin exactly that shit is exactly why.
But yes it is cool when others appreciate the effort and sweat that went into the 400.
The Bricky paid good money - he has already had a heap of fun on it, what more could a guy ask for from a toy.
His wife says is the best thing that has happened to him , apart from the kids, and they are debating that now.

Bikes are never about being sensible :lol: Hey Wob something interesting I realised while watching a Aston Martin Mega factory doco on youtube, designers were talking about the "golden ratio' which has been used since they built the Parthenon. The ratio of 'anything' should be 1.612:1 just under 1/3 to 2/3rds, designers say everything conforming to that has natural beauty and looks 'right'. Your header to t/l , diffuser to t/l and what to do with the remainder seems to conform with that 'golden ratio'.


http://en.wikipedia.org/wiki/Golden_ratio

[dinamik2t]

Wob, the RSA duct exit must be 39.2mm in equiv. diameter, from Frits' aprilia 102 pipe schematic 278678

From another cad drawing posted in pit-lane by Francis Payart -which I cannot find by any means at the moment-damn research - the exit is ~33x46mm tallXwide, auxiliary ½ moons included.

I cannot find a way that will make the main+aux ports around 1600mm², in order to have a duct exit of ~75% of that. The total of the ex ports would have to be around 45mm of equiv. diameter! Seems huge:(

Actually, when modeling the older apc ports, it would seem it is more like 40.5 ports - 39.2 duct; or ~95%. That % would be even bigger for the bottom-risen/narrowed apf port.

Could it be that the nozzle effect is only duct-volume related and not duct-exit% related?
Or perhaps the auxiliary ½ moons are excluded from that area%.. -which you have confirmed in the past it's not the case, I think.


p.s. I don't mean to insult you Wob; you have my respect. I am just discussing my thoughts, eh.. :drinkup:

edit: Here it is.. Just had to go through fpayart posts et voilà: 278679

[wobbly]

The 75% number came about from doing alot of testing on flanges and duct shape for a customer building aftermarket RS125 cylinders.
The best beta cylinder ended up with an oval at 41 by 32mm.
It was about this time I started doing alot of sims using Neels code, and it struck me that so many engines went the best - on the screen and on the dyno with that 75% idea.
Then I later confirmed that an oval to round transition within the spigot worked the best.
I have not had a chance to try Jans idea of continuing the 1/2 moon cutouts down into the header, making that somewhat oval as well.
Maybe Frits could shed some light on the area at the flange testing done at Aprilia.
Yes of course you cannot separate out the duct volume from the area at the flange - the two go hand in hand, but which one is the chicken and which is the egg?? I do not know, nor care, at this stage.
All I do know is that dozens of customers and hundreds of others have used the 75% rule of thumb and it works every time - way better than the over 100% seen so often..
Some engines like more - some less, but there have been, and will be even less in the future, those who can get even close to the specific output of the earlyer model Aprilia and will need a detailed analysis of EXACTLY what is best
for any given engine.
Try this for another rule of thumb - I have found that most full noise RACE engines built with single exhaust ports, like the exit area at the flange ( and thus the header diameter ) at 90% of the EFFECTIVE port area.
Again, this seems to work every time ( TZ350 ) but some like even less if the port is VERY high, like big drag race Kawasaki tripples etc.

[husaberg]

http://sharkshifter.com/zc/index.php?main_page=index&cPath=185_186&sort=20a&page=3
above is a random link not the TZ one
:msn-wink:
depending on your set up you may need to remove an extra http://

this triple port seems to be a great idea mmmmmm.......I wonder if it will catch on..................Maybe next week.
<img src="http://img853.imageshack.us/img853/7363/89413056.jpg" width="509px"/><img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=251856&d=1322825780" width="326px"/>
<img src="http://i32.servimg.com/u/f32/14/82/67/76/dsc06510.jpg" width="260px"/><img src="http://fpe-racing.pagesperso-orange.fr/Moteurs_fichiers/Cyl%20FPE1.JPG" width="365px"/><img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=277704&d=1359624836" width="505px"/>


Wob, the RSA duct exit must be 39.2mm in equiv. diameter, from Frits' aprilia 102 pipe schematic 278678

From another cad drawing posted in pit-lane by Francis Payart -which I cannot find by any means at the moment-damn research - the exit is ~33x46mm tallXwide, auxiliary ½ moons included.

I cannot find a way that will make the main+aux ports around 1600mm², in order to have a duct exit of ~75% of that. The total of the ex ports would have to be around 45mm of equiv. diameter! Seems huge:(

Actually, when modeling the older apc ports, it would seem it is more like 40.5 ports - 39.2 duct; or ~95%. That % would be even bigger for the bottom-risen/narrowed apf port.

Could it be that the nozzle effect is only duct-volume related and not duct-exit% related?
Or perhaps the auxiliary ½ moons are excluded from that area%.. -which you have confirmed in the past it's not the case, I think.


p.s. I don't mean to insult you Wob; you have my respect. I am just discussing my thoughts, eh.. :drinkup:

edit: Here it is.. Just had to go through fpayart posts et voilà: 278679

I always had suspicions that one one looked at what i posted:lol:

[dinamik2t]

Husa, no need to have suspicions on being neglected!
It just happened to first see those pics in pit-lane, so automatically my memory was linked to that web-page, in which I knew I could narrow down the poster's id and find them easier.


Wob, thanks for the patience of re-explaining everything. After all, you are right about achieving aprilia's specific HP...
It would be interesting to hear more about the paradox, but if we don't it 'll be ok too.


By way, I believe that the chicken came from one egg (or the egg came from one chicken). Evolution:D.

[Frits Overmars]

The 75% number came about from doing alot of testing on flanges and duct shape for a customer building aftermarket RS125 cylinders....It was about this time I started doing alot of sims using Neels code, and it struck me that so many engines went the best - on the screen and on the dyno with that 75% idea.As an empirical rule Wobbly's 75% of the total exhaust port area works very well. But I prefer to base the port exit area calculation on the blowdown area, not on the total port area. The drawings shown above by Husaberg, give a good indication of the port exit area; below you will find the Aprilia's blowdown area (and the angle.areas for blowdown and scavenging).


you cannot separate the duct volume from the area at the flange - the two go hand in hand, but which one is the chicken and which is the egg?? I do not know, nor care, at this stage.I bet you do care, Wob :msn-wink:. I think the duct should just be able to handle the flow during the blowdown phase; any more cross section area in the duct only increases its volume which should be avoided.


Try this for another rule of thumb - I have found that most full noise RACE engines built with single exhaust ports, like the exit area at the flange ( and thus the header diameter ) at 90% of the EFFECTIVE port area. Again, this seems to work every time ( TZ350 ) but some like even less if the port is VERY high, like big drag race Kawasaki tripples etc.Wobbly hits on an important point here: the higher the exhaust timing, the smaller the header diameter should be for a given rpm range. It would take me too far to explain the fundamentals here, but you can find the relationship in my 'simple exhaust concept' below.

[cookie1965]

There's been discussion in this thread about home made dynos. I got some sound advice regarding the Heenan and Froude water brake I have which I chose to follow. So I continued my plans to build an inertia dyno and then stumbled onto this:

http://i48.photobucket.com/albums/f224/cookie1965/11407AE0-274E-40CB-B566-64771F792C88-2143-0000031CA7B58345_zps31f75aca.jpg

http://i48.photobucket.com/albums/f224/cookie1965/D8D43F9A-892E-4790-9167-8DE5F10C46BA-2143-0000031CA2B716FB_zpsbaf99308.jpg

Hoping to get it dug out of the blackberry bushes and to my house soon so I can start working on it! Haven't seen any progress pictures of anyone elses dyno projects, how are they coming along?

[Yow Ling]

Hi Cookie,
there are 3 new dynos around the place, heres mine
Mine and the GPR ones use Dynomite software and Im pretty happy with it
you could have that dyno going in about 1 hour

278736278737

[Bert]

Hi Cookie,
there are 3 new dynos around the place, heres mine
Mine and the GPR ones use Dynomite software and Im pretty happy with it
you could have that dyno going in about 1 hour


Following previous comments; we are really happy with the performance trends' Dynomite interface and software.

[wobbly]

As always I have to agree with Frits analysis - tying the duct geometry to the blowdown is way more accurate - as this number is crucial to achieving the
power an engine will make in reality.
The Ex effective area is pretty much irrelevant, so having an empirical duct number ,based on an irrelevant dimension seems pretty short sighted, even if it is based on long term observation.
But reality gets in the way of desire, and busyness precludes the time needed to try and construct a good approximation for a duct based on Blow STA.

Yes I do care about the duct/area relationship, but as 95% of the time working on engines involves the huge compromises needed when modifying an existing, flawed design,
I again cant afford the time needed to work thru it.

Clean sheet designing is a huge challenge, as EVERY aspect is your fault, or your success depending upon the result, at least with an adapted design there are usually several loop holes for escape.

[husaberg]

Clean sheet designing is a huge challenge, as EVERY aspect is your fault, or your success depending upon the result, at least with an adapted design there are usually several loop holes for escape.
Engineering is all about making the right compromises (stole this phrase and i like it)

Design is unfortunately always a compromise the hardest bit is quantifying how to avoid the worst. Starting with a clean sheet makes you appreciate just how much is involved and what seems like an obvious flaw and first glace is maybe not as it seems and the designer was forced into it by some other aspect.
The other thing is when faced by a blank slate it is so much work.
It is sometimes easier (for my small brain at least)to fit something in to the fixed parameters of an existing design.
Which of course is a huge compromise?


The cleverest design is often as an afterthought seems so incredibly simple and blindingly obvious and offers the least amount of compromises where it counts. I also believe most often form and function are totally interrelated.

I can think of an engine from someone that was supposed to be an ace Race engineer that was copied entirely of another but as an afterthought he placed upside-down to seemingly mimic another design. Plus make it look "trick"
He it looked like in his rush to finish the job and get paid forgot to make sure the one important design aspect was up the right way.
Frits and Wob will have a pic somewhere i guess.

[cookie1965]

Hi Cookie,
there are 3 new dynos around the place, heres mine
Mine and the GPR ones use Dynomite software and Im pretty happy with it
you could have that dyno going in about 1 hour

278736278737

I'm glad to hear that, since I bought my kit from Performance trends too. I'm sure I could get it going in no time, but I'm going to modify it some to make it trailerable and lower.

[Flettner]

Talk on oils earlier, I use Motul micro T, synthetic model engine oil. But I don't fully trust it so I blend 1/4 castor with it. 350 does 4.5 Km per liter of fuel, E90 and suspect some transfers out the exhaust. I'm not sure if it's the right thing to do but the engine has done nearly 50 hours on this piston and bore ( cast iron ), all seems in good order inside. Not tooo much carbon build up. Air cooled ( and fuel ).

[wobbly]

Yep, here is the Rumi "upside down " reed engine with dead straight inlet ie done right, unlike Mr Ws half arsed attempt.
Then there is the Rumi rear valve - not alot done wrong there, but I dont know the detail.

[RAW]

Yep, here is the Rumi "upside down " reed engine with dead straight inlet ie done right, unlike Mr Ws half arsed attempt.
Then there is the Rumi rear valve - not alot done wrong there, but I dont know the detail.

Who knows the RUMI details ?
Frits your turn

[wobbly]

Here is another shot I found on EMOT

[husaberg]

Yep, here is the Rumi "upside down " reed engine with dead straight inlet ie done right, unlike Mr Ws half arsed attempt.
Then there is the Rumi rear valve - not alot done wrong there, but I dont know the detail.

This was the engine i was meaning it seems by the simple expedient of turning an existing kart upside down a "new Engine" was thus created.
If you look at the oil Breather/Filler housing and surround on the Kart engine (right pics in compliation), and compare then it to the Maxtra Haojue engine Drain plug, you will see what i mean.:lol:

The Rumi engines have there own thread on pitlane.

[koba]

This was the engine i was meaning it seems by the simple expedient of turning an existing kart upside down a "new Engine" was thus created if you look at the oil filler casting on the Kart engine and compare it to the Maxtra Haojue engine you will see what i mean.:lol:

The Rumi engines have there own thread on pitlane.

I can't work that one out, the image induces vertigo!

[F5 Dave]

this topic has been on here before,but just to put my 2 cents in i run R30 in my air cooled vintage MX 125 bikes on Av and pump with 5% acetone,and it is fine,AV gas is the safe way to go.Dave i can sell you R30 for $66.00 for 3 bottles 1LT or $122.00 for a box of 6.

chris RMS engineering 09 817 9500
Yeah Thanks Chris, I'll see where this all goes.

Had a funny meet, spent a couple of practice sessions running in trying not to get into any races with people. Then first race fouled a plug when I lined up for the start. New plug, did a race & scared the 4 strokes pushing past & gapping them. That felt good. Another race, rechecked plug, well its pretty dark, I had gone a couple of mains up to be safe with 15:1 oil & unleaded, that's cool, just want to finish day.

Out for next race 2 laps in it conks out on full throttle. Plug wet as wet, but a new plug doesn't fix it. Oh well. Back home head off, wet with oil, bore looks ok, no spark. Time for T.

Tonight, hmm, getting spark. Head back on & use my new ring seal leak tester. Hmm, pressure drops to zero, doesn't seem to be working & says 80% leak but shows no pressure & can't hear any escape.

There I am having poured scorn on compression testers & I have to dig my old one out. 170psi, well it seems a little low, but well high enough to run & I don't trust them anyway.

Lots of bangs when push starting, but I've run out of plugs, time to buy some new, but I'm fingering the CDI or stator. Must be that Castor oil wrecks ignitions:rolleyes:.

[dinamik2t]

Here's some more photos of the Rumi GP

http://2stroker.createforumhosting.com/viewtopic.php?f=5&t=2652&start=0&&view=print

Here's a relevant quote too from Jan Thiel: (auto translation from Dutch)


Rumi The engine was not a success but there were still some nice things, and also
some big drawbacks. The gearbox was designed by an artist who also
has signed a number of F1 engines. This tank had no seeger rings and washers and you
could him after removal of the cover without tools apart. There were also 3
different primary ratios, you could cover the primary disassembly without the ignition
rotor disassembly. The crankcase halves and the lids were sealed with O-rings. The engine is the cylinder downwards designed for 2 reasons. Rumi wanted an engine that was different from all others (no good reason) I myself had to Garelli once did a test with a kilo of lead in the tip of the keel of the fairing. Gresini found that the motor thus better sent, so I thought the cylinder down like a good idea. The carburetor was thus rightly at the place where normally the radiator sits. I thought this to fix the radiator in a different place to put behind us, under the tank. Something like the British did. The frame was made ​​by Nico Bakker, with even a monoarm swingarm for more space for the exhaust. The frame is also made ​​but were not collected nor paid. Rumi had a frame in Italy, with the radiator in the traditional place. Thus came the carburetor between 2 radiator little to worry about as a result poor cooling, hot air inlet and no place for a good airbox. Also, it was very difficult to place the outlet to find the thick part came up right where the footrest Sat We solved through a hole in the frame to make the exhaust was then in an s-curve before the rear wheel backwards along with the muffler under the seat. This went well but was very difficult to make. On the test bench to ensure no power cost. There were also problems with the mechanical Niese water pump 3.5 HP cost. A elektriese pump made ​​the ignition after a while too little power and the engine was badly began to walk. Rumi began increasingly to technology to interfere where I think he totally did not know, was also the organization of the team unimaginably bad. then also pay my salary a growing backlog was I decided only to disband, after eighteen months work.

Last but not least, another set of photos through the Rumi pits:
http://www.2t-special.it/forum/viewtopic.php?f=11&t=3333&start=10

Finally, an upside down pavesi :P
http://www.motoripavesi.it/img/motore_moto_6_big.jpg



ps. I have mentioned it before, but it is possible to search any pic through google images. it usually leads to more relevant photos and info. :)

[Frits Overmars]

Who knows the RUMI details ? Frits your turnSure. Much has already been said in Jan's Google-translated story above. But I'm not sure I would have understood one word of that Googletalk if I hadn't been there myself at the time and could reconstruct ill-translated Dutch words and expressions.
But I've got a problem: I can neither see nor post PNG-pictures on Kiwibiker. I run Windows 7 with Internet Exporer 8. On a friend's computer with Windows 7 and Google Chrome I can at least see the PNGs. Suggestions anyone?

[dinamik2t]

There you go Frits!

http://www.winhelponline.com/articles/202/1/PNG-images-are-not-displayed-on-Web-sites-in-Internet-Explorer.html

Win Vista > same kernel as Win7, Vista~=7.
Why not also try the IE 9, which is a much better and faster browser than IE8?

[Frits Overmars]

There you go Frits!
http://www.winhelponline.com/articles/202/1/PNG-images-are-not-displayed-on-Web-sites-in-Internet-Explorer.html
Why not also try the IE 9, which is a much better and faster browser than IE8?Thanks dinamik, but I get this: "Cannot import C:\Users\FOS\Desktop\pngasso_vista.reg: Not all data was successfully written to the registry."
The problem with PNGs refusing to show only occurs when I'm visiting Kiwibiker; all other programs function OK.

Why not IE9? Because Microsoft won't let me install it, saying I should first substitute my beta-version of Windows7 with the final version.
You don't happen to know a way around that, do you?

[breezy]

Hi I am selling this for a freind who has moved to New Zealand,
This is a 1989 KR1 with a tuned KR1S engine with dyno sheet showing 61hp,
The frame has a professionally modified Honda RS subframe to suit the RS seat unit and fairing mount to fit the RS fairing,
A RGV swing arm has been fitted and modified to fit the KR1 dog bones,
With a 17" RGV rear wheel,
Pro light discs,
New race clip ons,
Rear sets,
EBC race shock, plus the STD one,
ZXR 400 USD forks with maxton mods, front wheel & mudguard,
New earls front brake lines,
Pair of Dunlop KR364's just scrubbed in,
Plus boxes of spares include
Another runner engine with RS pistons which is seized,
Two good cranks,
Gearboxes,
Clutches,
Electrical,
Wheel,
Brakes,
Spockets,
New twin cable twistgrip,
Speedo with less than 500 miles,
Loads more!
V5 present

my mate has just had this off ebay... not sure if the real selling reason is true, but if the fella looks in on this site i can say its going to good home

[dinamik2t]

:sherlock:
Sorry, Frits, I don't know what is going wrong... Perhaps if you try right-click > run as admin ?

...if you turn your pm's on for a little, I can provide you with an MSDN win7pro code.

[Frits Overmars]

if you turn your pm's on for a little, I can provide you with an MSDN win7pro code.It's on, just for you.

[G Jones]

Why not IE9? Because Microsoft won't let me install it, saying I should first substitute my beta-version of Windows7 with the final version.
You don't happen to know a way around that, do you?M/soft :eek: - almost as bad as Hon*a....:rolleyes::rolleyes: (Whose computer is it anyway ??? :rolleyes:)
No reason you shouldn't use something other than the Exploder browser (Firefox / Opera etc) - a lot of them you can run without installing - just download & run them where & when you want.
I've not used the MS broken browser since version 5 - probably about 10 years ago....far better software available these days...
The PNG issue could be the server having an htaccess file restriction in place - you'd need to have the admin of the server fix that - if you see PNGs everywhere else - that's looking quite likely ?

[TZ350]

Page 720 .....


Wobs comment on inlet tract length.


And Just for you TeeZee I waded back a hundred pages or so and collected up Wobs comments on setting up 2-Stroke carburation.

Have to visit Buckets post to see the links.


Suzuki GP125 and GP125U service manual... all 136 pages of it. It's a large file at 18.0 MB

Suzuki GP125 Service Manual (http://christophercain.cc/b/suzuki-gp125.pdf)


There are ways of finding interesting posts without having to flick through all the pages.

On most decade pages 100 110 120 130 Etc ..... there is a links or interesting post collection.

Page 500 has a bit of an index and links to how to get 28-30 hp from a 125.

And if you use thread tools you can trawl through all the thousands of pictures on the ESE thread which then lead to the relevant post.


268048

A handy little tool put together by Bucket for checking the BMEP of different Engines.

You change the values in the yellow squares and the answers appear in the green ones. Its a great tool for compairing different bikes and what development potential they may have left and who's telling porkies.



I am sure Frits said somewhere if the tract is smaller it can be longer I think?
And I am sure I didn't. Quite the opposite in fact: if the tract diameter has to be small for some reason (rules), you can diminish its negative effect by making it as short as possible. And because it's a lovely day, here is my solution of making it really short.

I slip a plate (P in the drawing) around the carb. The hole in this plate is about 2 mm larger than the carb's outer diameter. Then I slip a thick O-ring O around the carb. Then I slide this composition into a hole in the disk valve cover D and fasten it with two bolts B.
Plate P compresses O-ring O which centers the carb in the disk valve cover so there is no metallic contact anywhere. With this solution I manage to fit the carb at 2 millimeters from the disk valve. It works with reed valves too.

279267

You can play with the O-ring size and the rate of compression to vary the flexibility of the carb mounting. You can also fit a second, smaller O-ring at the bevelled end of the carb, next to the disk valve, to keep the carb from sagging when applying a light rate of compression on the large O-ring.
The ideal would be an O-ring with a sleeve. Maybe you can produce something like that with 'liquid rubber'.


279268
An article that I wrote for a German two-stroke forum. It's in German (they like that in Germany)...


268124


I'd like to tell you about the events in the engine. Without calculating (it already expects
enough), but with logic, in a way that it can understand a 12 year old. This is just in the area
my knowledge of German.
Look at the picture some HFD-1.
There you'll see a cylinder. Above the piston is a volume VZYL and therein a pressure prevails Pzyl.
Then comes an exhaust manifold. It contains a mass of gas. The moves are not enough.
After the elbow is the exhaust volume Vout and the pressure is there Paus.
Now we consider what happens when the engine is running in thousandths of seconds. But we have
not in a hurry, we take the time to step by step to follow closely and rethink.
Case 1: The piston has just released the exhaust port. The pressure in the cylinder Pzyl is higher than the pressure
Paus in the exhaust. This means that the gas mass in the left elbow is more crowded than the right.
The mass will be accelerated on the right night. It flows from the gas cylinder in the manifold and thereby
the cylinder pressure drops Pzyl.
At the same gas flows from the exhaust manifold in volume, thereby increasing the exhaust pressure Paus.
As long as the cylinder pressure of the exhaust pressure Pzyl Paus is the gas mass in the manifold
accelerated and the flow velocity on the increase.
This goes on until Pzyl Paus is the same. Then the gas mass reaches its maximum speed.
Because the flow from left to right, ie running from the cylinder to exhaust, remains in the cylinder always
less gas left, so the pressure drops Pzyl ever. And the exhaust is it just the other way.
There is always flowing into it more gas, so that the pressure continues to rise Paus. Paus is therefore higher than
Pzyl. The right of the elbow will be more crowded than on the left and the flow in the manifold is always
decelerated more, until it completely stops.
The crowd is right now much stronger than the left, so the currently stagnant gas mass in the
Now bend to the left accelerates back to the cylinder.
The acceleration remains active until Pzyl Paus again is the same. Then the mass of gas has reiterated its maximum
Speed ​​is reached, but this time left. After growing Pzyl beyond Paus and after the
left flowing gas mass decelerated again until it stops.
Now we are back at the starting point: the cylinder pressure Pzyl is high, the exhaust pressure is Paus
lower, and the mass of gas in the manifold is stationary. She has now performed a complete oscillation of
left to right and back.
Case 2: Imagine that the cylinder volume is now twice as big VZYL. The cylinder is so much
more gas as in Case 1 Now, if gas from the cylinder flows in the manifold, the cylinder pressure decreases Pzyl
much more slowly. So down it takes longer now to Pzyl up at the Pau-value.
It takes longer to stop the flow. And then when the flow goes to the left, back to the
Cylinder increases, Pzyl at much slower and takes longer to stop this reverse flow.
Everything just takes longer.
Case 3: Let us now before the exhaust volume Vout also made twice as large. If dan
Gas from the exhaust manifold flows in, the pressure Paus also much slower. It takes longer to
the flow is slowed down to the right and the return flow comes to the left in motion. And so on.
Case 4: Now we do the Krümmerdurchmesser much smaller, as in Figure HFD-4.
The piston is released to the exhaust port. The mass of gas in the manifold is on the pressure difference
Pzyl-Paus back to the right and accelerates the flow velocity increases again. But because
the small Krümmerdurchmessers comes despite the gas flow rate less mass per
Second from the cylinder to the exhaust. The cylinder entlehrt So slowly, the pressure drops Pzyl
slower, the pressure rises more slowly Paus, everything is slower.
Case 5: the elbow regains its original diameter, as shown in Fig HFD-1. But now
we make, such as image HFD-5 shows the manifold much shorter.
All other values ​​VZYL, Pzyl, Vout and Pau are the same as in Case 1
The pressure difference Pzyl-Paus of the acceleration provides the mass of gas, is again the same.
But the mass itself is now much smaller! Therefore, it is accelerated harder.
The flow rate increases faster, the cylinder pressure Pzyl decreases faster and the exhaust pressure
Paus is increasing rapidly. The flow velocity reaches its maximum value is more likely, rather slowed down,
rather, the direction changes from right to left, there is also decelerated more. In short, the
whole vibration plays in less time.
Leak
Now to another topic. I have stated several times: gas flows from the manifold in
Exhaust volume, thereby increasing the exhaust pressure Paus. But even in HFD-1 image you can see the hook:
the tailpipe! The exhaust has a leak. It comes in. Although gas, but also some same time escaped.
Therefore, the pressure Paus not nearly as fast as you expect without the tail pipe like it.
The pressure in the exhaust behaves as if the exhaust volume would be larger in reality. And
the larger the pipe diameter increases slower Paus Paus, and the lower is the peak-
be. The final hole acts like a shock absorber in the system.
Far left of the images are somewhat remarkable: the overflow. Once the piston
the scavenging port releases, has not only the exhaust volume, but also the cylinder volume a leak.
The cylinder pressure drops Pzyl though because gas flows away from the cylinder above the elbow, but as soon as
Pzyl comes under the irrigation pressure, fresh gas is refilled. Pzyl decreases less rapidly so as to
closed transfer ports.
Once through the opening of the overflow valve, the cylinder volume is brought into communication with the crankcase volume,
Thus it behaves as if it were greater in reality. The vibration in
this coupled volume and tube-dan system is running slower, and the system frequency drops.
Now you have something to ponder:
An increase in volume of the exhaust system reduces the frequency.
A reduction of Krümmerdurchmessers well.
A shortening of the manifold increases the frequency.
An enlargement of the Spülsteuerwinkels lowers the frequency.
An enlargement of the tail pipe diameter reduces the frequency and weakens the pressure fluctuations in the
Exhaust.


I discovered the 135mm inlet rule of thumb on a TM125 MX engine used for 125 class kart shifter racing . It had a VF2 with a late model RS125 rubber manifold along with Kehin SPJ solenoid carb.
The old Dynamation sim I was using said shorter was better.

I really wanted 50 Hp and found an old model RS125 intake rubber - 20mm shorter, fitted that in a back to back,Voila more power everywhere in the useable range.
Each test is 3 pulls averaged.

That length is for a reed - the RV needs to be alot shorter again.


Oh no ..... :facepalm: ... it was hard enough to get down to 130 and EngMod2T points to 85mm Now I will have to look at Fritz's Idea.


Made a small adapter plate tonight to fit the pumper carb hard up against the case, can't get any shorter than that.

279271279272


The tuned intake length testing I did with the reed engine was based on Dynamation sim results and as I have shown here before,involves combining the case pressure ratio dropping below atma,at the same time as the intake length resonates with a + ratio at the reeds. This opens them real quick,and fast,initiating intake flow early in the cycle.

Having around 135mm from bell to reed tips gives a good result centred around 12,000 rpm so works well on alot of 125s.
This tunes the intake to the 2rd harmonic from memory as it gives the best energy recovery over the widest range.
Using this approach on a 250 power unit gives really good gains ( making the length around 50% longer again ) and proves that the only reason the factories use 125 size carbs and manifolds on these MX bikes ,is simply that there is no room.

Another pointer is that for example on the old TZ250 piston port. If you are silly enough to remove the 20mm phenolic spacer fitted by the factory to "get some more top end ", all that happens is the the tuning range moves up past 12,000
and it is impossible to jet the thing at lower rpm. Same with the tossers selling shortened carbs for the TZ350, simply throwing away a bunch of free mid power with no addition of any top end at all - the factory chose the big/long body Mikuni for a reason..

The RV scenario probably is working on the short 3rd harmonic, with less energy recovery, but also the very short length is mechanically desirable and reduces the deleterious effect of the standing waves on the fuel delivery from the jets.


You can have an intake length that is too short in combination with intake diameter, intake timing, crankcase volume and desired rpm, in which case the engine will express its displeasure by blowing back some of the inhaled mixture. I prefer to shorten the intake length as much as possible and shorten the intake timing accordingly.

By varying intake length, intake timing or crankcase volume you can adapt the induction system to different rpms. I think the best way to adapt to low revs is to advance the intake closing; it will make for a docile engine with a clean, easy to set carburation.

Varying exhaust pipe length seems to be a far better way of increasing overrev than retarding the ignition or leaning out the mixture; it would be a waste not to utilize all inhaled oxygen. Varying the pipe length can also markedly lower the beginning of the power band.


http://en.wikipedia.org/wiki/Exhaust_pulse_pressure_charging

Exhaust pulse pressure charging (EPPC) is a system for supercharging two-stroke of the loop-scavenge type. The exhaust system is arranged in such a way that excess air/fuel charge follows the exhaust gases into the exhaust manifold. Some of this air/fuel is then forced back into the cylinder by a rise in pressure in the exhaust manifold.

279260

http://en.wikipedia.org/wiki/Pressure_wave_supercharger

A pressure wave supercharger The process is controlled by a cylindrical cell rotor whose speed is synchronised with the engine crankshaft speed via a belt or chain. Individual cells alternately open and close the exhaust gas and fresh air apertures, when the aperture on the exhaust gas side is reached pressurised exhaust gas flows into the cell and compresses the fresh air there.

As the cell rotor continues to rotate and reaches the aperture on the inlet side the compressed air flows to the engine. Before the exhaust gas can flow the aperture is closed again and the exhaust gas column is reflected before entering the engine. The exhaust gas exits at high speed sucking further intake air into the cell behind it repeating the process.

Energy exchange in the pressure-wave supercharger occurs at sound velocity, resulting in good response even at low engine speeds, a common downfall of turbocharged engines. It combines the advantages of mechanical and exhaust gas supercharging.

http://www.idsc.ethz.ch/Research_Guzzella/Automotive_Applications/Gasoline_Engines/Pressure_Wave_Systems

279259

A ton of information on wave rotors can be found here:- http://www.egr.msu.edu/mueller/projects_waverotor.htm

So if a 2-stroke is already supercharged by the exhaust system, then would it be ok to extend the inertial pressure wave process to the inlet side?

[TZ350]

278896

Setting up for the first ever run, first cut came out at 20hp and climbed to 22 with header length adjustments.

The night was spent finding the right header length to get the rpm peak in the right place, hopefully 24 after ignition and jetting adjustments.

[cotswold]

278896

Setting up for the first ever run, first cut came out at 20hp and climbed to 22 with header length adjustments.

The night was spent finding the right header length to get the rpm peak in the right place, hopefully 24 after ignition and jetting adjustments.

you have got to be happy with that

[chrisc]

Nice one Kel!

[kel]

you have got to be happy with that
no :weep:
But it is making 22hp at 8500rpm so 24hp at 10500 is certainly achievable, just need to sort the exhaust, carb, ignition ...

Big thanks to TZ for the dyno time and advice :niceone:

[koba]

no :weep:
But it is making 22hp at 8500rpm so 24hp at 10500 is certainly achievable, just need to sort the exhaust, carb, ignition ...

Big thanks to TZ for the dyno time and advice :niceone:

That's grunty!

What's the spread like so far?

[F5 Dave]

Good greif, those are low revs for that sort of power, I'm certainly feeling a bit shamed that it has taken me so long to get just to that level.


However I got some sparks from my bike (sort of came & went) but Sketchy lent me a whole set up. I then dug a bit pulling back wires on my Stator & found then had eaten their way into each other just shorting which explains the failure I hope.

[FastFred]

I earn my living from developing AIR COOLED, TWO STROKE 125 (AND 140) CC CYLINDERS..............

Man, you guys are way behind....

278904

I Know what I am talking about.....



... it is making 22hp at 8500rpm ...

Congrats Kel, sure SS90's was a few years ago but you equaled his best "Tuning Industry" efforts at that time on your first try and you don't even work in the Industry, shows what a bit of intelligent research on the net can achieve, good one :niceone:.

[cotswold]

I was trying to get to this weekends fun day in Auckland with my 1/2 finished GP but could not get it running right, I have put a video on youtube as the file is from an Ipad and I also cant make that work for this forum.

http://youtu.be/eaHpanau3Yw

It starts, idles and revs with the choke open, when the choke is off it backfires and dies, I am on 125 main and the needle on the top clip, I ran out of jets at 125 but am I right in thinking it's still too lean?

Kx100 ignition set by the suck it and see method


It was my CDI, Tee Zee lent me one of his old ones and it now sounds great.

[TZ350]

Ok, finally found the time to pop the head and barrel of after Taumarunui, piston ring is still free and there are no piston seizure marks, now that makes a change. The damage to the head was from a previous mis adventure.

I will put the thing back together and run it up on the dyno again, I am keen to find a way to stop it detonating in over rev. I would like to try a few ideas, like water injection and a dump valve on the chamber to bleed of pressure during over rev.

[twotempi]

I see that TZ350 doesn't use a fine wire plug.

There are theoretical advantages such as requiring less voltage to fire BUT are they the "magic bullet" or a "required plug for racing" as promoted by the plug manufacturers OR are the more common wide electrode quite satisfactory for our state of tune engines.

I have always used the fine wire type but .........................................

[TZ350]

I see that TZ350 doesn't use a fine wire plug.

I have always used the fine wire type but .........................................

I got heap of the ordinary 1/2" reach ones for a few bucks of Ebay. But plans are afoot for using good fine wire resistor plugs, but that type are mostly 3/4" reach so some head modification is required.

[TZ350]

The old BR10EGV isnt prone to ceramic cracking at all, and the 7376 at 4 times the price of those is virtually indestructible.

The brown bit on the insulators nose is the colour of the ash left by the plug keeping itself clean by burning off lubricating oil and impurites in the fuel.

278921

The yellow arrow points to the blackish fuel mixture ring and is where you need to look after a plug chop to check the size of the main jet.

And Wobs comments ....


Is this still running AvGas??
For Av its a bit rich, for Unleaded its a bit lean.
The plug heat range appears good, and the mixture is on the rich side of correct for Av.


Weld a threaded alloy bung onto the head ( you could even machine a couple of fins into it ) to enable use of 3/4 reach race plugs, and use the NGK 7376 I gave you. Much easier to read both ignition and fuel and is worth an easy Hp or two over shitter plugs.

[2T Institute]

Search is on for this obscure Marben 2C engine looks for all intents to be a 125cc version of the Rotax 256 inline. :lol:
Brought back to 100cc would be the ideal engine with 2 KTM 50 cylinders.

[Flettner]

Why muck around with some other obscure engine, just make a new one. It's not that hard to do. Just make patterns and cast, that way you get just what you want and cheap too. TZ 350 don't modify your old head, bondie it up ( the old one ) and copy cast it with all the extra length for threads etc.

This is a copy cast of the original then remachined, original had no squish and two side plugs. This is a better design!!

http://i1056.photobucket.com/albums/t380/uniflow/babe0419.jpg

[Flettner]

TZ 350, have you a dyno? Would it be able to run a 350 Kawasaki ?

[husaberg]

I guess you have seen this.
EGA 125

Built by Jan Eggens from Assen raced from 1980? to 1986
Best result = 12 place at the TT-Assen 1985.

<center><img src=" http://www.emot.nl/fotoalbum/albums/userpics/10002/ega.jpg" height="360px"/><img src=" http://farm2.static.flickr.com/1160/1391992241_c949ef8716.jpg" height="360px"/>


<img src=" http://farm3.staticflickr.com/2731/4279166388_6db31083bb_o.png" height="360px"/><img src=" http://forum.limburgracingteam.nl/uploads/monthly_01_2011/post-582-129527266568_thumb.jpg" height="360px"/>

<img src=" http://farm2.static.flickr.com/1282/1391992255_6fbe9ec875.jpg" height="360px"/>



TZ 350 don't modify your old head, bondie it up ( the old one ) and copy cast it with all the extra length for threads etc.

This is a copy cast of the original then remachined, original had no squish and two side plugs. This is a better design!!



And add a decent amount of radial fining.........
http://www.emot-oldparts.nl/webshop/images/uploads/Afbeelding_306.jpg

<center>



Then came the 1969 MZ 125 RE II (shown below). This bike features for the first time a tandem design, with two cylinders located in a front-to-back configuration. It was put into service in 1970 in the 125cc World Championship. Its greatest achievement was a third place at the Isle of Man TT, earned by factory rider Günter Bartusch. The following year, MZ withdrew from FIM World Championship 125cc class. The development cost of the highly specialized engines was too much for Walter Kaaden's budget to bear. He just could not get the funds he needed from the MZ board. The specifications are: two-cylinder two-stroke, 43mm x 43mm bore and stroke, 34 horsepower at 11,500 rpm, six-speed gearbox, and top speed of 128 mph.

<img src="http://i62.servimg.com/u/f62/15/92/36/87/img_4411.jpg" height="340px"/><img src="http://www.emot.nl/fotoalbum/albums/userpics/10002/DSCF3436.jpg" height="340px"/>

<img src="http://www.classic-motorrad.de/autoren/Quaas/mz-sinsheim-2/web/mz-sinsh-26.jpg" height="340px"/><img src="http://www.motohistory.net/images/1969MZ2resized.jpg" height="340px"/>

<img src="http://www.classic-motorrad.de/autoren/Quaas/mz-sinsheim-2/web/mz-sinsh-25.jpg" height="340px"/><img src="http://i62.servimg.com/u/f62/15/92/36/87/img_4410.jpg" height="340px"/>

<img src="http://i62.servimg.com/u/f62/15/92/36/87/img_6910.jpg" height="340px"/>

[Flettner]

Why are the cylinders offset like this? sideways.

Husaburg, have you got your stuff now? Can I see it?

[husaberg]

Why are the cylinders offset like this? sideways.

Husaburg, have you got your stuff now? Can I see it?


Yes stuff is sorted and yes of course, i will take some pics today. (the camera is all sorted too i think?)

here is a preview.
It also looks like the local floundowndry is also better equipped than i initially assumed as well :).

[cotswold]

It was my CDI, Tee Zee lent me one of his old ones and it now sounds great.

http://www.youtube.com/watch?v=PvAQAOSsLCc

[Frits Overmars]

Why are the cylinders offset like this? sideways.Because the disk valves are overlapping, as in most tandemtwins. In the 250 cc Rotax that gave unequal inlet lengths; in the 125 cc EGA these lengths were equal.

[Yow Ling]

Yes and yes of course, i will take some pics today. (the camera is all sorted i think)

here is a preview.
It also looks like the local foundowndry is also better equipped than i initially assumed as well :).

Looking pretty flash !

[Flettner]

http://i1056.photobucket.com/albums/t380/uniflow/DSCF4343_zps8817a558.jpg

My tandem rotary valves are offset only 2.5mm. There is a small slice of alloy that separates the two discs, they can't communicate. In this setup it was nessesary, one piston up one down but in a counter rotating unit it wouldn't matter if the valves communicated. So long as they don't touch.

[2T Institute]

Why muck around with some other obscure engine, just make a new one. It's not that hard to do. Just make patterns and cast

Just the "time poor" bit that cancels that out for me :(

[Flettner]

http://i1056.photobucket.com/albums/t380/uniflow/IMG_0840_zps1abd3238.jpg

Lozza, finally got time to finish the drum for the YZ 250 EFI project. Had the CNC shell the component to 2mm thick.

http://i1056.photobucket.com/albums/t380/uniflow/IMG_0841_zps6788cd75.jpg
http://i1056.photobucket.com/albums/t380/uniflow/IMG_0839_zps693d7aa0.jpg
http://i1056.photobucket.com/albums/t380/uniflow/IMG_0842_zpsc2f55a24.jpg

[teriks]

Looks like a sophisticated version of a small R/C engine carb, minus the terrible fuel metering. :niceone:

[TZ350]

Current Race Results Table in XLS format courtesy of Dave D

278979

and I have posted the results of the days racing in PDF format.

[2T Institute]

Bloody hell Neil that looks awesome. The shaft on either end looks to be interpolated out how were you holding it?

[jasonu]

Current Race Results Table in XLS format courtesy of Dave D

278979

and I have posted the results of the days racing in PDF format.

I see No Mates dnf'd AGAIN and after meeting him last Sunday I see where the nick name comes from. Good to put a couple of faces to names though. I made the comment to my wife that the average age of the riders at Mt Welli is a lot older than when I was involved. She pointed out that I fit in the very same age group...

[TZ350]

Good to put a couple of faces to names ...

It was great to meet up, after all this time talking on the net.

[TZ350]

I see No Mates dnf'd AGAIN ...

This time, haven taken the lead Nigal dnf'd by crashing out trying to lower his lap record of 29.436 (anti clockwise) that he set in race 1.

His bike sounded sweet all day but it wasn't as easy a win in race 1 or all that easy to take the lead in race 2 as I would have thought, Gavin and his FXR150 sure look hard to beat at Mt Wellington.

In the first pre lim race Nigal crashed trying to out ride Av, Nigal re mounted to finish and he won the second prelim, Av DNF'd the second with mechanical problems.

Av, having got a shocker of a start in race 2 because of a oiled plug (the engine started sucking gear box oil big time), when she got going Av turned in a faster lap than anyone else and cut through the traffic to finish 2nd close behind Gavin, maybe if there had been another lap or three she could have pulled it off.

From where I was sitting it looked like Av and Nigal became less about winning than competing with each other to see who could set the fastest lap time.

[F5 Dave]

Yeah I was just remembering Jase was supposed to be in NZ by now? Pity you couldn't have been down this way for the NI round 4 at Kaitoke.

[wobbly]

No Mates DNF'd again due to being No Mates,the engine ran fine with no issues, when he finally believed the gauge and went down 5 jet sizes.
Busting the lap record with no oil in the front forks, and fighting wheelspin around the sweeper every lap due to shit rear suspension, deserves maybe a little respect.
Not mindless shit slinging for the sake of it.

[kel]

Not mindless shit slinging for the sake of it.

Nigel certainly looked fast (and all over the place) He must be pleased to get through a weekend without a seizure :lol:

[Frits Overmars]

Busting the lap record with no oil in the front forks, and fighting wheelspin around the sweeper every lap due to shit rear suspension, deserves maybe a little respect.I would agree the engine deserves maybe a little respect. And maybe the rider could not afford a decent rear shock. But no oil in the front forks.....:facepalm:

[speedpro]

http://i1056.photobucket.com/albums/t380/uniflow/IMG_0840_zps1abd3238.jpg

Lozza, finally got time to finish the drum for the YZ 250 EFI project. Had the CNC shell the component to 2mm thick.

http://i1056.photobucket.com/albums/t380/uniflow/IMG_0841_zps6788cd75.jpg

A slightly different setup I liked the look of is to have the inner alloy part fixed with the port lined up with the outer and a thin steel sleeve that rotates between them with a matching port. Kept the throttle inertia down and made a 4 throttle body setup easier to make and lighter.

[F5 Dave]

Oh I think he's well capable of slinging the shit back, in fact he rang a couple of hours back, I said I'd pass on the link as by his own admission he was too useless to find it:lol:.

The question is; is he going to show up to the GP this year? He mumbled something about packing a lunch. If Tokaroa has an Early bird meal deal at the local Cobb we could be in trouble.

[speedpro]

No Mates DNF'd again due to being No Mates,the engine ran fine with no issues, when he finally believed the gauge and went down 5 jet sizes.
Busting the lap record with no oil in the front forks, and fighting wheelspin around the sweeper every lap due to shit rear suspension, deserves maybe a little respect.
Not mindless shit slinging for the sake of it.

His EGT was way down initially suggesting going gown a few jets. The forks were what got me. He screwed the dampers fully in and it only made a tiny difference, if any. Bouncing the front end bottomed the forks easily. No wonder the back was lifting off braking for the corner at the end of the straight, and the back wasn't much better. The guy Nigel referred to as "coach" seemed to have a pretty good handle on it.

[cotswold]

No Mates DNF'd again due to being No Mates,the engine ran fine with no issues, when he finally believed the gauge and went down 5 jet sizes.
Busting the lap record with no oil in the front forks, and fighting wheelspin around the sweeper every lap due to shit rear suspension, deserves maybe a little respect.
Not mindless shit slinging for the sake of it.

He was riding bloody well and for someone over 50 to put in laps like he did it should be an inspiration for us more mature riders.
Take note he is looking forward to the next GP :eek5:

[Forgi]

Hi Everybody!

Thanks TeeZee, I can't wait for the results! :-)

Thanks Wobbly for the detailed explanation! I have been trying to find the 'truth' for a long time, but now I have had a chance to do some dyno tests on the exhaust nozzle, and it works! I haven't got results for simple exhaust port, but I plan to do some tests, although you say that it won't work, I'd like to see it for myself.

From now I really don't care the causes, cos it works, and that's all! Of course I have two possible explanations, but I think it's pointless to explain.

Otherwise have you tested an area smaller than 75%?

By the way what is your opinion? The blowdown could be too huge, or we have to try to make it the biggest possible anyway and anyhow?

And one last question to Wobbly: what is your opinion about the transfer theory? (the direction of the scavenging, vertical, horizontal angles etc.) Frist has already wrote a great article about it.

[TZ350]

Av, having got a shocker of a start in race 2 because of a oiled plug (the engine started sucking gear box oil big time), when she got going Av turned in a faster lap than anyone else and cut through the traffic to finish 2nd close behind Gavin, maybe if there had been another lap or three she could have pulled it off.

279052

Av nearly couldn't get it away and was a 1/2 lap down but she got going and managed to finish in second place.


From where I was sitting it looked like Av and Nigal became less about winning than competing with each other to see who could set the fastest lap time.

279051 Av 21 279050 Nigal

Because of the difficulty starting, winning wasn't possible so the rivalry between Nigal and Av became all about best lap times.

Photos from http://www.kiwibiker.co.nz/forums/showthread.php/153656-Chris-Bucket-photo-thread-Bandwidth-warning?p=1130506334#post1130506334

[wobbly]

Now we have the tools to accurately predict the correct blowdown needed for a desired power output, then of course we get people wanting to go "to big " , as always, more must be better.
When the blowdown is too big for the engines tune, then all that happens is the mid power drops dramatically.
Best example is the RZ350/Banshee big bore kit sold on Ebay for bugger all by Athena.
This is in effect an RZ350 copy , with no powervalve, and extra eye ports added.
It has NO midrange at all, compared to a stock Banshee, and although the added blowdown may help the bigger displacement, the other ports are stock, so it is useless.

Re the 75% nozzle "rule ".
This works in most cases very well, but of course it is based as I said before on the effective total Exhaust area.
Basing the nozzle on the Ex ,that is in effect irrelevant, is dumb - but is all we have at this time.
If the Ex area is large, then 75% of large is too big.
If the Ex area is small - compared to the strict calculated numbers for STA, then the 75% may in fact be too small.
This hasnt happened to me yet, as most people havnt started to fill in the bottom corner radi, or raise the port floor, to reduce the duct volume and or reduce short circuiting, thus making a very small port.
But the few engines that I have done - like Rossi 125 hydro outboards, work very well with a small port, HUGE aux , and 75% nozzle.

[no mates]

I would agree the engine deserves maybe a little respect. And maybe the rider could not afford a decent rear shock. But no oil in the front forks.....:facepalm:

there was some oil in there, just not enough

[F5 Dave]

ahh, its only there to stop the squeaking;)

[speedpro]

Should probably put some oil in Rob's gearbox then going by the noises it was making when Av came into the pits.

[F5 Dave]

Bit of that going around, my 50s clutch bearing was looking pretty dry, sadly I'd drained the oil into a large sump container so not sure how much came out (it was pouring out then I walked away). Time for crank seal leak test.

[jasonu]

Yeah I was just remembering Jase was supposed to be in NZ by now? Pity you couldn't have been down this way for the NI round 4 at Kaitoke.

I was planning on going to the Manfield back track but it was cancelled. Not enough hours in a month to see and do everything.

[jasonu]

Take note he is looking forward to the next GP :eek5:

Probably because it isn't on a big track...

[no mates]

Probably because it isn't on a big track...

I will take any size track now fellas, problem identified and solved
no mates

[husaberg]

sorry i couldn't resist:lol:

Welcome aboard Nigel tell us about the bike, RG125 sleeved to 100?

[Yow Ling]

My brain is not big enough for this, but there are people here who have brain mass to spare

Borrowed from another place in the ether
"I found some very excellent software at Autodesk. It is a beta test of Computational Fluid Dynamics (CFD) software. It is a wind tunnel simulation. This is a stand alone program so you don't need anything else. Very unfortunately the beta test runs out on March 15 next month. Fortunately there are still almost three weeks to play with it. This is very easy to use software with no math required at all. You may insert models in 2D as simple JPEG or PNG shapes or as full 3D models from just about any software. I use Sketchup and export the 3D model as an STL file. There is a free plugin for that. It works perfectly.

The program is Falcon and is available here: http://labs.autodesk.com/utilities/falcon"

Here is a link to the source http://bbs.homeshopmachinist.net/threads/58151-The-Tailgate-question-revisited-An-investigation-using-CFD

Should be good for keeping you up at night

[no mates]

sorry i couldn't resist:lol:

Welcome aboard Nigel tell us about the bike, RG125 sleeved to 100?

RG150 with a RG250 barrel to get it down to 56mm then a steel sleeve to get down to 50mm
currently 98cc
motor is six years old now
numbers by Wob ( port timing, head shape, pipe dimensions)
assembly by me (when its broken, or Wob when its taking lap records apparently)
have had i bit of bother with nippin up on tracks where you spend a long time wide open, But I (if it fails, or Wob if it doesent) reckon its cured now
been on dynos anywhere between 23 and 28.3 hp, power from 8500 to 1200, nice flat easy to use neddies.
mid eighties RS125 chassis with standard rear end and undermaintained front end

Nomates

[koba]

I will take any size track now fellas, problem identified and solved
no mates

Haha, nice.

I have identified my problem, time to try and solve it. Perhaps I should start by smacking myself in the head... :facepalm:

[crazy man]

Haha, nice.

I have identified my problem, time to try and solve it. Perhaps I should start by smacking myself in the head... :facepalm:we have all done this . to far advance or lean

[koba]

we have all done this . to far advance or lean

The headsmack come from me knowing this BEFORE I WENT OUT!
I had checked the plug, looked a bit hot, asked Dave for his experienced opinion and he said go richer.
I knew it, I dismissed it thinking; ahhh it's not that far off and BOOM!


I've always bee conservative in jetting and timing but was starting to push things further as I thought I was too prudish.

Lesson learned!

[Neal]

@ Koba - what plug were you using ?

[Forgi]

Now we have the tools to accurately predict the correct blowdown needed for a desired power output, then of course we get people wanting to go "to big " , as always, more must be better.
When the blowdown is too big for the engines tune, then all that happens is the mid power drops dramatically.

Re the 75% nozzle "rule ".
This works in most cases very well, but of course it is based as I said before on the effective total Exhaust area.
Basing the nozzle on the Ex ,that is in effect irrelevant, is dumb - but is all we have at this time.
If the Ex area is large, then 75% of large is too big.
If the Ex area is small - compared to the strict calculated numbers for STA, then the 75% may in fact be too small.
This hasnt happened to me yet, as most people havnt started to fill in the bottom corner radi, or raise the port floor, to reduce the duct volume and or reduce short circuiting, thus making a very small port.
But the few engines that I have done - like Rossi 125 hydro outboards, work very well with a small port, HUGE aux , and 75% nozzle.

Thanks for your detailed explanation!

Well of course the '75% rule' depends on the shape of the exhaust port...it is obvious, it could be too much or too little but I think that the ideal size could be determined only by testing.

As I didn't have my own observations I have shaped the blowdown according to Blair's recommendation. It seems that it works, but I haven't tested it yet. If you have any experience or result please let me know, I'd be grateful!

[koba]

@ Koba - what plug were you using ?

B10ES

I wad a 9 before that, the only change I had made was going to a Ten.
It was a hot day and I started shifting erlier before one high speed corner and pulling through under more load, at lower revs, than I had been before.

[speedpro]

Koba's piston brings back memories. Many suzuki TS and Honda MB pistons of mine have ended up looking like that.

[wobbly]

Neels code, EngMod 2T will predict exactly what size nozzle is best, you simply keep making it smaller, and when no more power appears on the screen
you can be sure it will work in reality.
That code uses a version of Blairs numbers for correct STA I believe.

[crazy man]

The headsmack come from me knowing this BEFORE I WENT OUT!
I had checked the plug, looked a bit hot, asked Dave for his experienced opinion and he said go richer.
I knew it, I dismissed it thinking; ahhh it's not that far off and BOOM!


I've always bee conservative in jetting and timing but was starting to push things further as I thought I was too prudish.

Lesson learned!you do that when you want to go faster . l have done it at least 5 times looking at old pistons l have piss me off. young and stilly at the time and prombly go back there if l went 2 stroke again like l have one. 4 strokes you seem to get away with murder but still seen it happen there

[TZ350]

279234

I have been busy working on my new lighter bike.

279235

To use the light weight all alloy triple clamp I need to fit a bigger top bearing. The new top bearing is the same size as the original bottom one and I had thought of building up the bearing area by welding all around the top then boring it out.

But TwoTempi took a look and suggested a better and neater way would be to mill the top portion away and weld in a pre machined sleeve. Might even be able to alter the stearing head angle that way too.

[Ocean1]

weld in a pre machined sleeve.

I've seen a lot of welding done on alloy bike frames, as far as I'm aware none of it's been subsequently heat treated. Anyone know for sure what the alloy is and how much of a problem the weld heat completely annealing it is?

[husaberg]

I've seen a lot of welding done on alloy bike frames, as far as I'm aware none of it's been subsequently heat treated. Anyone know for sure what the alloy is and how much of a problem the weld heat completely annealing it is?

Up to about 1998 on the Hondas it seems ok. the later ones not so much.
This holds true for the CR250's anyway in my experience.

[chrisc]

Sigh. I can't sleep.

Here you go guys, a Suzuki GP125 and GP125U service manual... all 136 pages of it. Thanks to Rob for the manual and may it serve to help many in their journey towards 2 stroke euphoria :drinkup:

Be patient, it's a large file (for those who still use windows 98) at 18.0 MB

Suzuki GP125 Service Manual (http://christophercain.cc/b/suzuki-gp125.pdf)

I posted this a while back but a flood of activity swamped the page just after I posted it. I just wanted to make sure everyone that may be able to get some use from it saw it was there.

There's the link for you Rob and sweet work on the NSR frame, it's going to be such an improvement over the FZR setup!

[husaberg]

279234

I have been busy working on my new lighter bike.


To use the light weight all alloy triple clamp I need to fit a bigger top bearing. The new top bearing is the same size as the original bottom one and I had thought of building up the bearing area by welding all around the top then boring it out.

But TwoTempi took a look and suggested a better and neater way would be to mill the top portion away and weld in a pre machined sleeve. Might even be able to alter the stearing head angle that way too.

Rob while you are playing with the steering head. consider placing shims so you can alter the effective height of the steering had and therefor angle cog and weight distribution without playing with the forks.
I would suggest splitting the shims say 25mm each between the top and the bottom for a start with a longer steering head stem so you can have a greater amount of adjustability in the future.

The RC45 had this feature (not a great example i guess):nya:
I hope you can make sense of what i are meaning.
This can still be combined with the eccentric cups.

PS not sure why you had to change the steering head? wouldn't altering the stem be a little easier?

Also lastly remember if you are altering the stem if pressing in a new one you can add more rake by not having the stem add 90 degrees to the yoke.

[Forgi]

Hi Everyone!

Is there anybody who has got experience how much extra power makes a rotary disc valve or reedvalve compared with the capacity of a piston port inlet, if every other conditions are 'constant'? Is there anyone who did such a transformation and did some dyno tests?

In case of a piston port, if the port timing is reasonable the STA couldn't be more than 0,0130-0,0150. Concerning the other two cases above, in general the STA is between 0,0200-250. In theory all of this should mean a huge difference, but in practice we don't get what we expect.

[husaberg]

Hi Everyone!

Is there anybody who has got experience how much extra power makes a rotary disc valve or reedvalve compared with the capacity of a piston port inlet, if every other conditions are 'constant'? Is there anyone who did such a transformation and did some dyno tests?

In case of a piston port, if the port timing is reasonable the STA couldn't be more than 0,0130-0,0150. Concerning the other two cases above, in general the STA is between 0,0200-250. In theory all of this should mean a huge difference, but in practice we don't get what we expect.

Frits posted this a while back about 10% food for thought.( i am sure mr Frits mentioned Jan got the Derbi Reed to about 49 hp later) the Derbi i think owed a lot to the Honda RS125 is that right Frits?
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=261462&d=1333621581

by piston port i assume you really meant reed. ANd crankcae reed at least if not well pure piston port finished about the TZ350 era.... so no idea.

[TZ350]

Rob while you are playing with the steering head. consider placing shims so you can alter the effective height of the steering and therefor angle cog and weight distribution without playing with the forks. I would suggest splitting the shims say 25mm each between the top and the bottom for a start with a longer steering head stem so you can have a greater amount of adjustability in the future. This can still be combined with the eccentric cups.


Thats a very good idea, thanks.

279254

The replacement rear shock that I am going to fit has a ride height adjuster so I expect to be able to use that for stearing head adjustment by jacking the back up.


PS not sure why you had to change the steering head? wouldn't altering the stem be a little easier?

279253

I have this lovely light triple clamp with an alloy stem that goes with some nice forks that I want to use. The stem is a little shorter than the original heavy one, and the new stem is a larger diameter at the top so some modification is required. The ESE workshop is more about fabrication than precision engineering so cut and weld is a more practical option.

[twotempi]

Be afraid, very afraid. TZ 350 and his new bike is going to get very much quicker

TZ350 has been to Jenny Craig and is losing weight very fast.

In fact if we graph it he will have a weight of 0.00 kg and completely :rolleyes::rolleyes: disappear about Easter next year !!

[Buckets4Me]

Be afraid, very afraid. TZ 350 and his new bike is going to get very much quicker

TZ350 has been to Jenny Craig and is losing weight very fast.

In fact if we graph it he will have a weight of 0.00 kg and completely :rolleyes::rolleyes: disappear about Easter next year !!


problem is with his riding ability slipping and age getting the better of him will he still be able to get on the faster lighter bike ? (love you Dad)

who is going to ride the new lighter faster BEAST ?

[TZ350]

who is going to ride the new lighter faster BEAST ?

Who indeed ..... :D

[TZ350]

279300279301

No, not going over to the Scooter side, just picked this up off Trademe for its engine and CVT parts. It has done stuff all K's so must have been a demonstrator before being cannibalised for parts. Bucketracer has relisted all the bodywork, forks and wheels on Trademe.

Now I have the shafts, reduction box and other parts that I have been looking for, for my CVT project. I plan on making a special 30+ rwhp water cooled 100cc rotary valve engine to go with the CVT unit.

And I hear Gigglebutton is making real progress on a very light and very special darkside project.

[cotswold]

Who indeed ..... :D

Someone not born in the 60's would be an excellent starting point. :whistle:

[TZ350]

Someone not born in the 60's would be an excellent starting point. :whistle:

Does that mean born in the 50's would be OK .... :laugh:

[cotswold]

Does that mean born in the 50's would be OK .... :laugh:

Kenneth Leroy Roberts born December 31, 1951, he might go ok?

[koba]

What is Wayne Gardner doing these days?
He was born in the '50's too...

[Yow Ling]

Give Garry McCoy a run, he's a young dude !


http://www.youtube.com/watch?v=7arxrEPoBVI

[chrisc]

http://4.bp.blogspot.com/-XSsSBp9Iitg/USyJTagogYI/AAAAAAAAFQI/JSuGb2osiIY/s1600/tumblr_mgqt34FYdM1r0ve58o1_500.jpg

[TZ350]

279355279354

A bit of wisdom from Stan Stephens.

[F5 Dave]

http://4.bp.blogspot.com/-XSsSBp9Iitg/USyJTagogYI/AAAAAAAAFQI/JSuGb2osiIY/s1600/tumblr_mgqt34FYdM1r0ve58o1_500.jpg

I was just thinking I needed a new backdrop on my desktop - thanks. Slightly higher res would have been nice.

[kel]

Darkside project

279362

:sick::sick::sick:

[2T Institute]

279355279354

A bit of wisdom from Stan Stephens.

8HP from "flowing" (grrr I hate that term:mad:) alone ?

[chrisc]

I was just thinking I needed a new backdrop on my desktop - thanks. Slightly higher res would have been nice.
This is as big as it gets I'm sorry:

960x789 pixels (http://24.media.tumblr.com/f52bd3cb34c990adbc2f6881a04db9b8/tumblr_mgqt34FYdM1r0ve58o1_1280.jpg)

[F5 Dave]

That's good enough to be used, thanks again.

[TZ350]

279376

With a bit of cut and shut and general lowering this could be a dark-side, chair.

[TZ350]

Chambers is looking to use a pumper carb on the 50 he is prepairing for NedKelly. Plenty of clearance all round and a direct shot into the crank case.

[koba]

Chambers is looking to use a pumper carb on the 50 he is prepairing for NedKelly. Plenty of clearance all round and a direct shot into the crank case.

Just a thought, maybe a nicer radius on the outside of the Bell-mouth in those pics?

Maybe a pumper will help with my RS fitment woes...

[TZ350]

Just a thought, maybe a nicer radius on the outside of the Bell-mouth in those pics?...

Thats a standard gocart bellmouth and is shaped like that to go with a regulation cart airbox, I am not sure what Chambers is going to do but he has been talking about making an airbox to suit the RS frame.


Maybe a pumper will help with my RS fitment woes...

The Tillitson HL360A is 24mm (0.945") and is sure easy to fit into tight spaces. No rubber mount is required, you can bolt them hard up against the case, although a heat insulating manifold block could be helpful.

I am a bit of a fan of these carbs, I got mine from here:- http://www.out2win.com/catalog/tillotson.html

279385

I ran the pumper like this, without any bellmouth and made 28+ hp

279384

It ran very well at the Taupo GP on the old track but I took it off when I started to knock on the door of 31+hp as the carb seemed unable to flow enough fuel. I have since obtained a bigger diaphragm needle jet and parts to make it into a double pumper, so look forward to trying it again.

[Flettner]

Don't piss around, EFI it.

[timg]

Darkside project

279362

:sick::sick::sick:
That'll never work. Can't be done. Sacrilege. I'll find it a good home :drool:

[husaberg]

http://4.bp.blogspot.com/-XSsSBp9Iitg/USyJTagogYI/AAAAAAAAFQI/JSuGb2osiIY/s1600/tumblr_mgqt34FYdM1r0ve58o1_500.jpg
beautiful

Darkside project

279362

:sick::sick::sick:

An abomination a crime against nature...................:weep:

[richban]

An abomination a crime against nature...................:weep:

He he thats funny. Looks like another 4 stroke weapon in the making.

[speedpro]

Two people at least have surprised me going over to the dark side. I'm waiting for Rich to build a fast 2 stroke. I'm envisaging a 125cc watercooled engine.

[speedpro]

This is another example of exhaust pipe art. Jim Steadman's 750/3 that he built, bottom pipe. It does a reasonably tight loop straight out of the port before snaking aft. Pipe built by Nomates.

[wobbly]

I did the design of Jimmys pipes and yes NoMates built the top two - nice job as well.
The bottom pipe was in no way art - it was nowhere near the correct dimensions when blown and NoMates and I want no association at all with its deluded, unnamed constructor.

[F5 Dave]

Wish I'd taken some pics of Nigels V4 500 pipes, they were nice. Actually the whole bike was a cool project.

[mbsteven]

Here is a set of Ti pipes I built for my V4 500
http://i675.photobucket.com/albums/vv114/yzr500steve/DSC02406sm_zps5f393268.jpg

[Gigglebutton]

He he thats funny. Looks like another 4 stroke weapon in the making.

Weighed it on Saturday. 70kg 60% front 40% rear. :yes:

Motor is only 21hp on the ESE dyno. Plans are a foot for a short stroked fuel injected FXR engine

[F5 Dave]

Nice work. ~89TZ frame with latter SW? Tasty.

[crazy man]

Here is a set of Ti pipes I built for my V4 500
http://i675.photobucket.com/albums/vv114/yzr500steve/DSC02406sm_zps5f393268.jpgnice job . wish l bought a rz500 motor years ago . just to lazy to pick it up

[speedpro]

I did the design of Jimmys pipes and yes NoMates built the top two - nice job as well.
The bottom pipe was in no way art - it was nowhere near the correct dimensions when blown and NoMates and I want no association at all with its deluded, unnamed constructor.

Hell, I always thought Nige built it after the whinging he did about building Jim's pipes. The top pipes didn't seem to justify all the complaining.

[jasonu]

Weighed it on Saturday. 70kg 60% front 40% rear. :yes:


If you are refering to the pic Kel posted of the NX4 frame with the FXR motor I call BULLSHIT!!!

[husaberg]

Wish I'd taken some pics of Nigels V4 500 pipes, they were nice. Actually the whole bike was a cool project.

this was way back

http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=251591&d=1322369484

Bill built a V4 - 500 that used YZ125 parts, with a pressed and welded frame.
It wasnt very clever, and he didnt like it when I said to him in the tent at Manfield that the guy who made the pipes should be shot.
I was with Mike Sinclair, Mike Webb and the other Mike the suspension guy from here in Tauranga.
They all told Bill to start again, and eventually he did.
When Loren and I turned up to start the project, he wanted us to finish the prototype, but as I pointed out there was no place to put the water pump,so that sealed its fate - bin it.

Another laugh I had was over Briggsy designing and building all the pipes, more rubbish.
I was so busy trying to get the engine rework done - I taught him what to do, and gave him the laser'd pattern designs and he welded and hammered some of the final few sets up, including some Ti ones.
Made some real nice ones too.
Jason Monopoly worked for John B, then came to us at BSL for 6 months.
He did all the glass styling/design work, and off that Roly made some stunning bodywork that worked well in the wind tunnel testing we did at AK Uni.
But alot was changed when Mike Sinclair mused about sidewind effects at 300Km/H

Nigels bike we worked on and off for about 10 years,going in fits when he had some money.
It was a pretty thing, as you can see from the pipes,but Nige finally gave up on trying to finish it - its gone to Rodent in Queenstown


Yeah it was. Frame supposedly an RGV500 copy, I was very impressed at its handmade appearance. RG500 converted to V configuration, RGB dry clutch, wanky gearbox, reputably ex works bit suspension etc etc. He offered it to me about 3-4 years back when he realised he would never have time to finish it, & I was tempted. But had to be realistic, it needed some serious skills to finish things like inlet manifolds machined for V config, there was just too much to do custom made. So instead I opted for something simple like a CPI barreled RZ in a hybrid frame.:facepalm: Hey I rode it today.

[crazy man]

If you are refering to the pic Kel posted of the NX4 frame with the FXR motor I call BULLSHIT!!!fxr motors are cow shit not bull lol

[Gigglebutton]

If you are refering to the pic Kel posted of the NX4 frame with the FXR motor I call BULLSHIT!!!

No bull. Just checked it with the scales again. 30kg rear 40kg front.

[cotswold]

No bull. Just checked it with the scales again. 30kg rear 40kg front.

What does the heavy bit in the middle weigh ??? :lol::lol::lol:

[Buckets4Me]

What does the heavy bit in the middle weigh ??? :lol::lol::lol:
more than the tank of gass and seat that still has to be put on it :rolleyes:

[cotswold]

more than the tank of gass and seat that still has to be put on it :rolleyes:

Still very impressive.

[richban]

What does the heavy bit in the middle weigh ??? :lol::lol::lol:

25-28kg. Depending on what's inside or not inside. If you can get it to 85 finished that will be good.

[Neal]

this was way back

http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=251591&d=1322369484

Where can I read the story about this bike ?

Thanks

[speedpro]

Originally it was a square 4 motor but Nige made new top cases to fit the cylinders on in a V formation. He also made the frame himself, as I understand. He also had some rather nicer carbs for it than those pictured. As has been said though there was a lot left to do and the sad thing is it probably never will be finished and run.

There's a V6 750 being worked on, sort of, as well. The crankcase patterns are pretty well done but work has stalled due to other commitments. I understand Nigel has been approached about making the pipes but he's having his nails done that weekend, or something.

[husaberg]

Where can I read the story about this bike ?

Thanks


Yeah it was. Frame supposedly an RGV500 copy, I was very impressed at its handmade appearance. RG500 converted to V configuration, RGB dry clutch, wanky gearbox, reputably ex works bit suspension etc etc. He offered it to me about 3-4 years back when he realised he would never have time to finish it, & I was tempted. But had to be realistic, it needed some serious skills to finish things like inlet manifolds machined for V config, there was just too much to do custom made. So instead I opted for something simple like a CPI barreled RZ in a hybrid frame.:facepalm: Hey I rode it today.

click on the arrow for the post preceding and after the ones i have added or ask no mates.


I will take any size track now fellas, problem identified and solved
no mates

re the story of the bike?

[jasonu]

No bull. Just checked it with the scales again. 30kg rear 40kg front.
Plus the atleast 10kg of stuff/fluids you still need to add. Looks good though. I was hopeing to be the first to do a 4 stroke NX4 bike.


25-28kg. Depending on what's inside or not inside. If you can get it to 85 finished that will be good.
That is about what I think the finished weight will be.
If our (latest) project actually happens (see Chris Pickett) we are hopeing for around 78kg as the CBR motor is a few kgs lighter than the FXR.

[kel]

If our (latest) project actually happens (see Chris Pickett) we are hopeing for around 78kg as the CBR motor is a few kgs lighter than the FXR.

And it will be top heavy just like that dark side project I posted. Was amazing how unbalanced it felt compared with the light weight two stroke RS parked next to it (oh yeah that was mine wasn't it, guess I might be slightly biased :lol:), time will tell I guess.

[TZ350]

Tided up my desk today and found the full set of results for the 2011 F4 GP when it was run recently on the old Taupo track.

[crazy man]

just out of intrest
fxr150 40 kg rear and 42 front . engine oil but no fuel279454and the aprila 550 (-; weght so far is 34 kgs rear 36 front .. motor is the same weght as a fxr 150 he he279455guessing when the aprila is finshed it should be hopfully no more that 2kgs heaver than the fxr

[wobbly]

Trumpet blowing time - get the jetting on the money, ie 1232 /1236 degrees F and another RZ400 F3 whizzes around Taupo for 4 - 30 minute sessions.
Wheelspinning off turn one, then running wide on turn 2 even shortshifting as the front is now in the air.
Happy customer, happy builder.
No the plating isnt shit, no, forged pistons dont sieze for no reason and yes I can tune my way out of a brown paper bag.
Issue now is the 160 rear Pirrelli is shreaded, needs more tyre and better than a poxy 4.5" Aprilia alloy road rim.
Bring on the BST carbons and a 180 rear.

[F5 Dave]

And a thin chain, further offset to just miss:sweatdrop? Well my 250 chassis build struggled with the 150 tyre, one assumes the April has more room.

Sounds like good problems to have,

[TZ350]

Good One Wob ..... :niceone:

[diesel pig]

I have been using the 36mm keihin with TPS and the wobbly powerjet mod with some success over the last six months on my 100cc bucket. Now the bucket is starting to go well I am going to start working again on a larger capacity Two Stroke project and since I am going to use a igntec on it I would like a 38mm or 39mm keihin with TPS and a solenoid powerjet to go with it. So before I go looking on e-bay is there a particular dirt bike that has a carb like that?

[husaberg]

I have been using the 36mm keihin with TPS and the wobbly powerjet mod with some success over the last six months on my 100cc bucket. Now the bucket is starting to go well I am going to start working again on a larger capacity Two Stroke project and since I am going to use a igntec on it I would like a 38mm or 39mm keihin with TPS and a solenoid powerjet to go with it. So before I go looking on e-bay is there a particular dirt bike that has a carb like that?

97-98 Honda cr250 has a tps PJ carb. from memory the Kawa KX250 (Added later from 99 actually)
yams and ktm from around the same era has the flatslide tps PJ but why so big?

For best results do a picture search or have a look at the Parts Fiche.
From memory later hondas went to Mikuni TMX with no pj and later Kawas ditched the Powerjet.

I think the Kawa carb (99-2000ish )and some of the KTM were shorties. (as you have noticed the 36mm is rather smaller than most others i guess)
But won't the KX125 36 bore to 38 anyway?

Maybe what you may want is the late Honda RS125 Carb Wob will ad what its called i can't remember had an S though?

After a bit of Net research it seems (if you can trust the net) that the KTM may be able to stand a higher level of down draft std and has a different bowl pick up but unconfirmed only

[dinamik2t]

YZ250 's -past '99- are Keihin PWK 38 with TPS/PJ. Also RM250's, but I don't know which years.
The same carb is also on KX125 I think. -edit: on 98~00 models, in 36mm diameter
All are short PWM bodies, some with Shindengen solenoids, others with Keihin solenoids. Some PJs have a cutout at the end of the tube, some have a hole at the rear, near the end of the tube.

The PJs can be removed, as Wob said in the past, with a 3 or 4 mm drill, pushing from the side towards the bore. It's just press fit.
Even if you damage the brass tube you can cut and insert a new one. If I remember correctly, the tube has an OD of 3mm and and ID of 1.8mm.

[RMS eng]

Plus the atleast 10kg of stuff/fluids you still need to add. Looks good though. I was hopeing to be the first to do a 4 stroke NX4 bike.


That is about what I think the finished weight will be.
If our (latest) project actually happens (see Chris Pickett) we are hopeing for around 78kg as the CBR motor is a few kgs lighter than the FXR.

CBR150 motor in the NX4 frame will take a bit of work to keep it under 80KG ,but i think we can get it done with alot of light parts,but if you can get a FXR150 motor in a NX4 frame down to 70 KG,that is well done,but that means if i put my RG50 motor in the NX4 RS125 frame to get some track time and try to beat Dave T ,it would be around 56KG.RG 50 14KG FXR150 28KG =14kg ,70 -14=56 kg

[quallman1234]

Darkside project

279362

:sick::sick::sick:

Its pretty funny, how obvious where these frames came from... With the painted wheels etc
Cool project.

[F5 Dave]

CBR150 motor in the NX4 frame will take a bit of work to keep it under 80KG ,but i think we can get it done with alot of light parts,but if you can get a FXR150 motor in a NX4 frame down to 70 KG,that is well done,but that means if i put my RG50 motor in the NX4 RS125 frame to get some track time and try to beat Dave T ,it would be around 56KG.RG 50 14KG FXR150 28KG =14kg ,70 -14=56 kg
My 50 actuallly got slightly heavier when I put it in the RS (was 59.5 in the RG50 or what was left of it).

All a bit spoiled as I'm almost 80kg now. I could get back to 75 if I avoided the beer wine & weekend pies, but feck it.:oi-grr:

[TZ350]

Model aero engine carburetor, about 9mm bore.

279495279496

I have been having trouble with detonation in over rev and I hope to cure it by bleeding some of the pipe pressure off when the engine is running in the detonation zone.

Sometimes stingers/mufflers have been attached here at the fattest point on the pipe because the pressure wave is at its lowest amplitude and quietest so I guess I can bleed pressure of from here without upsetting things and being to noisy.

Might get a chance to try it out in a day or two.

[wobbly]

I simply dont get it TZee.
A million 2 strokes have run at seriously high Hp levels without silly bleed systems needed to stop deto at high rpm.
The basics are combustion control and ignition advance.
With a properly designed toroid, or bathtub chamber, then deto is kept in control as good as it can be.
If that dosnt have the desired effect then pulling out advance is the next step - with the aside of needing at the minimum a 10.5 plug due to the high inherent temps being used, at 30 Hp levels.
But again, pull out advance and the EGT will rise, thus needing richer jets to keep the temps in the ball park.
This all assumes you have the correct com for the fuel quality - just another variable.
Get it all right and the effects are synergistic, lots of HP,get one wrong and it will all turn to sheeeite.
Helpful eh.

[TZ350]

We did ignition timing, air correction and main jet size to death on the dyno and at Taumaranui without success.


2 strokes have run at seriously high Hp levels without silly bleed systems needed to stop deto at high rpm.

279498

Frits proposed this bleed system, thought I should at least give something like it a try.......

Its not something I dreampt up without thinking about it, and this is what influenced my thinking.


Kel sent me this ......

jan thiel on part throttle deto

"I am 100% convinced our engine could have run for 6 hours at max power without seizing.
The problems arise when you close the throttle, or run part throttle!
The piston is mainly cooled by the transfer flow.
And at part throttle there is less transfer flow, causing detonation (auto ignition)
The entering fresh charge is ignited by the remaining, hot, burned gases!
You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? I did not find a solution before I retired.
And nobody else was really interested.
At 100% throttle the engine was undestructible!
By making the transfer ports as wide as possible we had very good piston cooling."

No answer here but at least we are not alone with engines that fail on part throttle

I scraped the full coversation below from here:- http://www.pit-lane.biz/t3173p60-gp1...vermars-part-2

Brian Callahan
Jan or others, how did you control the tuned pipe wall temperature (or EGT directly?) when testing on dyno? This seemed the most difficult thing to mimic when testing either the GP engines at QUB or my R/C boat engines, in the lab. The inertial dyno or computer controlled brake seem to work best because we can match the test engine's acceleration with reality. On steady-state testing, EGT would simply climb 500, 600, 700, 750 °C until way past reality and the piston would seize.

Frits Overmars
This has always been one of Jan's greatest handicaps. He has asked for an inertial test bench over and over, but Aprilias race director Witteveen, or The Great Leader as we call him, never deemed it necessary....

Jan Thiel
When EGT goes up and up there should be some serious problem with the engine.
We never had pistons seize during our steady state tests.
Working on the dyno continuously 5 days a week!
I am 100% convinced our engine could have run for 6 hours at max power without seizing.
The problems arise when you close the throttle, or run part throttle!
The piston is mainly cooled by the transfer flow.
And at part throttle there is less transfer flow, causing detonation (auto ignition)
The entering fresh charge is ignited by the remaining, hot, burned gases!
You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? I did not find a solution before I retired.
And nobody else was really interested.
At 100% throttle the engine was undestructible!
By making the transfer ports as wide as possible we had very good piston cooling.

As Frits has written, I would have liked to have also a dynamic testing possibility, with a flywheel.
In my opinion you should simulate a straight, starting at around 10.000 rpm, and shift through the gears
until you reach top speed. And with the airbox as used on the bike, with a ventilator that simulates the raising
air speed as it would be on track! Maybe it is interesting to know that without a ventilator the engine gave
less power with the airbox fitted.

I was told that such a testing system was too expensive.
And unnecessary as we won anyway!

I can also see a disadvantage of 'dynamic' testing.
Because the duration of the test is so short you can get away with very extreme (too extreme?) settings,
without damage.

GrahamB
Remember that retarding the ignition is used at high rpm to increase exhaust temps and effectively shorten the pipe. So it's likely to increase the heating of the front edge of the piston...

Haufen
Yes I know, but part load egt is usually lower than full load egt. And I think most of us would prefer higher part load egt over part load detonation. Of course, how far one could go and how far one would need to go would have to be tested, and how much would be needed would depend on the engine.

Mic
How about much larger travel on the exhaust power valve.
With a shorter exhaust port duration power is lower. And this is already controlled with the stepmotor over the ECU.

Jan Thiel
This causes detonation (auto ignition)
The problem is that the burned gases do not exit the cilinder!
Retarding ignition also does not make sense.
As you have an AUTO-inition problem!
So the engine does not 'listen' to its ECU anymore!
What you would need is the same fresh gas flow, but with less HP!
Not easy to achieve!
A variable tailpipe might help.

Jan Thiel
Haufen, We also had such a test bench at Aprlia.
The prototype of this test bench was developed by Apicom in collaboration wit Aprilia.
So we had it first, and now anyone can buy it.
It was helpful but not what I wanted.
A so-called step test.
And without the airbox!

Frits Overmars
Like Jan wrote, a shorter exhaust duration will worsen the detonation. What happens is this:
During normal operation, the blowdown time.area of the exhaust ports is sufficient to drop the cylinder pressure below the crankcase pressure before the transfer ports open, even at high rpm.
At part-throttle that cylinder pressure will drop to the same level, but now the crankcase pressure is much lower and exhaust gases will enter the transfer ducts, contaminating and heating the fresh mixture even before it enters the cylinder.
A theoretical solution would be a power valve that enlarges the normal exhaust timing instead of lowering it. But that is impractical as it would ruin the shape of the exhaust duct and it would cause cooling problems in the cylinder's exhaust area.
A variable tailpipe area, like Jan says, can be a more practical approach. I designed a simple solution, shown in the drawing below, but then two-stroke development at Aprilia was terminated because of Dorna's ban on two-strokes

Howard Gifford
Another way to lower HP without sacrificing piston cooling would be to richen the mixture when you want to lower the power. With a signal to a fuel enrichening solenoid you could achieve a power range. It would then be instantaneous and programmable. Not enviornmentally friendly but would work for racing. The mixture ratio difference from high power to low power would need to be just rich enough before a misfire and just lean enough for sustained high power.

The variable tailpipe idea will work but I suspect the pipe temperature would drop off and it would take several seconds to regain full power. But then again rich mixture may have the same problem.
Two strokes are like redheads. Hard to figure out and very temperamental. But when they are happy they are a lot of fun!
HG

Jan Thiel a écrit:
The entering fresh charge is ignited by the remaining, hot, burned gases!
You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? I did not find a solution before I retired.
And nobody else was really interested.

Institute of TwoStrokes
On aftermarket ignitions I use there is a mode I can switch on where a number of indivdual sparks are cut, depending on throttle position. It is now only configured for cutting 1 in every 3 sparks on over run(tps <10% with high rpm). Would that sort of system solve the part throttle detonation? If the number of sparks cut could be varied along with TPS for this to begin and end? If it would be helpful I'm certain the manufacturer would only need a software change to do this.

Jan Thiel
I certainly thought about cutting sparks.
But remember: the problem was AUTO-ignition!

GrahamB a écrit:
Remember that retarding the ignition is used at high rpm to increase exhaust temps and effectively shorten the pipe. So it's likely to increase the heating of the front edge of the piston...

Jan Thiel
Indeed, retarding too much caused detonation!

Institute of TwoStrokes a écrit:
Jan Thiel a écrit: The entering fresh charge is ignited by the remaining, hot, burned gases! You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.
This still is an unresolved problem! I was thinking about a way to reduce engine power without closing the throttle. But how can you do this? On aftermarket ignitions I use there is a mode I can switch on where a number of individual sparks are cut, depending on throttle position. Would that sort of system solve the part throttle detonation?

Frits Overmars
As Jan pointed out, once you have auto-ignition, the engine does not listen to its ECU any more. So you would have to start skipping sparks well before the onset of detonation.
In a foul-stroke your proposed system does work, but a two-stroke would react far from linear. For example, if you skip 1 in 4 sparks, you will loose much more than 25% of engine power because that one missing spark will cause the gasdynamics processes to collapse. The main problem would be to realise a smooth transition from intermittent to full ignition.


Jan Thiel a écrit:
Retarding ignition also does not make sense.
As you have an AUTO-inition problem!
So the engine does not 'listen' to its ECU anymore!
What you would need is the same fresh gas flow, but with less HP!
Not easy to achieve!
A variable tailpipe might help.

Haufen
I think I expressed myself unclearly. What I meant was the following:
Imagine your engine with the throttle opened just above the auto-ignition range. Then you have sufficient transfer flow, but too much power. To lower the power, now retard the ignition. Then you still have sufficient transfer flow, but with less power.

I think Honda used auto-ignition to their advantage on two-strokes. As far as I remember they did it with a (very) variable exhaust power valve.

Frits Overmars a écrit:

Mic a écrit:
How about much larger travel on the exhaust power valve. With a shorter exhaust port duration power is lower. And this is already controlled with the stepmotor over the ECU.

Frits Overmars a écrit:
Like Jan wrote, a shorter exhaust duration will worsen the detonation. What happens is this:
During normal operation, the blowdown time.area of the exhaust ports is sufficient to drop the cylinder pressure below the crankcase pressure before the transfer ports open, even at high rpm.
At part-throttle that cylinder pressure will drop to the same level, but now the crankcase pressure is much lower and exhaust gases will enter the transfer ducts, contaminating and heating the fresh mixture even before it enters the cylinder.
A theoretical solution would be a power valve that enlarges the normal exhaust timing instead of lowering it. But that is impractical as it would ruin the shape of the exhaust duct and it would cause cooling problems in the cylinder's exhaust area.
A variable tailpipe area, like Jan says, can be a more practical approach. I designed a simple solution, shown in the drawing below.

269228

Haufen
I think I have not gotten behind the variable tailpipe idea, yet. What would you like to vary with it and to achieve which effects? At little throttle openings the pressure inside the exhaust pipe is already very close to atmospheric pressure (if not even) on most engines. And if you had say 100mbar inside the pipe at the critical throttle opening, then the engine might have had more power with a bigger tailpipe.

269228

Frits Overmars
'Opening' the end of the reflector will cause a substantial weakening of the reflected pulse and thus less charging of the cylinder. Izze simple, no?

Haufen a écrit:
Variable transfer timing would be nice also, if feasible.

Frits Overmars
That would be my ideal. Lowering all the transfer roofs would shorten the transfer timing and lengthen the blowdown timing, so the cylinder pressure would drop further before the transfers would open. It would cure the hig revs/low power-detonation and it would improve the power band because a too early-returning exhaust pulse would have less opportunity to push the fresh cylinder contents back into the crankcase.
A controllable transfer height would even make a throttle valve unnecessary.
There's only the little problem of how to build it...

Jan Thiel
Haufen, Auto-ignition usually occurs between 10 to 40% throttle at high revs.
In fast, non full throttle corners.

Retarding the ignition was tried to diminish power.
This makes the exhaust very hot.
Then, when you need full power, it is not there because the exhaust temperatures are wrong.
This takes a little time, when the engine is back to full power you are already at the end of the straight!
The same goes for water injection in the exhaust.
It was tried by Rotax about 25 years ago.
There was a LOT more power at low revs, so the rider had to take it easy when opening the throttle.
But the engine revved a little bit less, because the exhaust temperature did not recover at high revs.
And lap times became actually slower.
After a day of testing the system was switched off.
Lap times immediately improved!

A very important thing when accelerating is the power you have after changing gear.
Spark interruption may be not so good for this!
As I did not have the dyno I wanted this gearchange effect could not be tried on the dyno, very regrettably!
Retarding the ignition and weakening the mixture by powerjet can also have a negative effect on this.
The exhaust temperature should be 'Right' for the No. of revs after you change gear.
If the temperature is too high there will be less power!
So it is REALLY complicated!

[Neal]

It would be interesting if you pinpoint the cause of the detonation and it points to part throttle at high revs . When i raced small bikes on kart tracks the style was either full throttle to your brake marker , shut off , change gears , lean for the corner and bang on the throttle again . No 1/4 - 1/2 throttle anywhere on the track . The corners are so quick that if you blink you are exiting the corner already .
Kinda like riding a skateboard in the bath .

I am sure you will find the cause of the det , rather sooner than later !

[kel]

It would be interesting if you pinpoint the cause of the detonation and it points to part throttle at high revs . When i raced small bikes on kart tracks the style was either full throttle to your brake marker , shut off , change gears , lean for the corner and bang on the throttle again . No 1/4 - 1/2 throttle anywhere on the track . The corners are so quick that if you blink you are exiting the corner already .
Kinda like riding a skateboard in the bath .

I am sure you will find the cause of the det , rather sooner than later !

We have found the cause of detonation and its part throttle at high revs! The pistons destroyed from me holding the throttle part open more than proved this (yes we had tried jetting, timing, and everything in between)
If you ride from full throttle to no throttle and nothing in between then you're simply not going as fast as you could/should be.

[bucketracer]

Its not that clear from what TeeZee posted, but this is a rpm related deto problem that happens at full throttle and well past peak power, ie well into the over rev zone where the power is dropping off. From memory, when he shuts the throttle its worse briefly until the rev's drop, maybe as little as 500 - 750 rpm. It happens on the dyno and at the track, bigger jets and fiddling with the TPS 3D ignition map did not cure it.

[Frits Overmars]

Its not that clear from what TeeZee posted, but this is a rpm related deto problem that happens at full throttle and well past peak power, ie well into the over rev zone where the power is dropping off. From memory, when he shuts the throttle its worse briefly until the rev's drop, maybe as little as 500 - 750 rpm. It happens on the dyno and at the track, bigger jets and fiddling with the TPS 3D ignition map did not cure it.Makes sense to me. 'past peak power, well into the over rev zone' it's not only the power that is dropping off; so is the blowdown time.area. That may result in a cylinder pressure above the scavenging pressure when the transfers open.
Nice affirmative detail: 'when he shuts the throttle its worse briefly until the revs drop'. That makes sense too: closing the throttle will lower the scavenging pressure, aggravating the problem of spent gases entering the transfer ducts, polluting and heating the fresh charge.
A simple cure might be to radius the timing edges of the auxiliary exhaust ports.

[TZ350]

I think we have the concept of the TPS and 3D ignition map nailed.

This over rev deto thing is another problem. Next time on the dyno I will try to get a video of the det sensor lights and dyno screen together so we can clearly see whats going on and if lowering the pipes internal pressure at high rpm helps.

Thanks Frits and Wob for your help, you have given me a bunch of ideas to work on.

[Haufen]

Did you make sure it's really detonating? Maybe something else on the frame is causing the deto sensor to ring the alarm. As far as I understand it, that deto problem you are describing was there from the beginning when you first installed the deto gauge. Are there any other signs of detonation? On an aircooled engine you might be able to hear the detonation, too. Does it occur when the deto sensor is monted in a different place, too? Does it stop flashing the lights immediately when you hit the kill switch on the dyno?

I was once dealing with something similar, sounded just like an engine screaming for help. After a long search, I found out that something else made that sound which sounded exactly the same, and occured in the corresponding speed and load range, too.

[Frits Overmars]

...This over rev deto thing is another problem. Next time on the dyno I will try to...see whats going on and if lowering the pipes internal pressure at high rpm helps.
Thanks Frits and Wob for your help, you have given me a bunch of ideas to work on.My pleasure, Teezee. Note: the initial blowdown flow is sonic; lowering the pipe pressure will not have any influence on the flow during this phase.
What helps is more blowdown angle.area (wider and/or higher exhaust ports) and improving the flow coefficient by radiusing the upper port edges.

[wobbly]

I wasnt making any inference that you or Frits were silly with that remark, its just that I am sure there will be a solution to the overev deto issue
without adding complexity that no one else has deemed as necessary.
Maybe when into the overev with a high Hp air cooled , the ignition retard that was needed initially to heat the pipe up, isnt needed, and in fact is over heating the plug of gas
in the header, that gets stuffed into the cylinder.
This overheated plug of gas then appears as deto in the squish later in the cycle.
I know from my dyno work that flat lining the timing after power peak prevents the egt from keeping on rising with rpm, past peak power.
In your case try reversing the curve, with a rising timing curve past peak power,of say 3*to 5* between peak power and peak rpm.
This will cool the gas temp in the header, and just maybe kill the deto issue.

[Frits Overmars]

Wobbly has a point here. limiting the ignition retard yields cooler exhaust gas which may even result in your whole engine running cooler.
And in case you fear a loss of overrev, consider lowering the compression ratio. Helps against deto too...
(and in case you fear a loss of power, you could be pleasantly surprised)

[TZ350]

Did you make sure it's really detonating? Maybe something else on the frame is causing the deto sensor to ring the alarm.

Very possible, and is one of the things I am looking for.

[TZ350]

I know from my dyno work that flat lining the timing after power peak prevents the egt from keeping on rising with rpm, past peak power.

In your case try reversing the curve, with a rising timing curve past peak power,of say 3*to 5* between peak power and peak rpm.
This will cool the gas temp in the header, and just maybe kill the deto issue.

I will try that, thanks.


What helps is more blowdown angle.area (wider and/or higher ports) and improving the flow coefficient by radiusing the upper port edges.

I will look at the radius next.

[2T Institute]

If you ride from full throttle to no throttle and nothing in between then you're simply not going as fast as you could/should be.

A fellow who I'll call a 'multiple 125cc GP winner' told me that is exactly how you have to ride a 125, off and 100%.

Adding some advance after peak would limit rpm a bit to.

[F5 Dave]

Not wanting to be a wanka (but it comes naturally so there you go), a kart track & a full size track do require some different techniques.

Being a fellow I'll call a multiple 50ccGP winner (because this is the internet I'll omit that I mean just nationally;)) I still find on some kart tracks there are occasions that I am not full throttle on a tiddler.

Being realistic either way most of us are nowhere near world level so don't ride like that - so its a mute point.

[teriks]

Wobbly has a point here. limiting the ignition retard yields cooler exhaust gas which may even result in your whole engine running cooler.
And in case you fear a loss of overrev, consider lowering the compression ratio. Helps against deto too...
(and in case you fear a loss of power, you could be pleasantly surprised)
One can get one of those pleasant surprises from running ridiculously low compression in the MB40 too.
Now that's a completely different beast with compression influencing ignition timing, but anyway.

[Buckets4Me]

A fellow who I'll call a 'multiple 125cc GP winner' told me that is exactly how you have to ride a 125, off and 100%.



so compairing a rs125 at pukekohe to a bucket at MtWellington is probably much like compairing a gsxr100 superbike to an rs125 at Pukekohe. And I know you dont ride them full throttle all the time. You would be highsiding the bike EVERY corner on the exit if you did that, or you would be waiting so long after the exit to get full power on that you may as well push the bike.

cracking the power on to hard or early on the exit of the corners will throw you off just ask Nigel about that.

[TZ350]

279495

I have been having trouble with detonation in over rev and I hope to cure it by bleeding some of the pipe pressure off when the engine is running in the detonation zone.


A million 2 strokes have run at seriously high Hp levels without bleed systems needed to stop deto at high rpm.

I confused the pipes internal working pressure as set by the stinger/nozzle with the return pressure wave that Frits talkes about.



Jan Thiel
The problem is that the burned gases do not exit the cylinder!
A variable tailpipe might help.

Frits Overmars
A variable tailpipe area, like Jan says, can be a more practical approach. I designed a simple solution, shown in the drawing below.

269228

'Opening' the end of the reflector will cause a substantial weakening of the reflected pulse and thus less charging of the cylinder.


So my pipe bleed idea may not reduce over rev deto, but now that I have it I will still give it a try and see what happens.



Howard Gifford
Another way to lower HP without sacrificing piston cooling would be to richen the mixture when you want to lower the power. With a signal to a fuel enriching solenoid you could achieve a power range. It would then be instantaneous and programmable.


Fuel enriching sounds like an idea to try too.

[Flettner]

With EFI you can " artificially " enrich the mixture where ever you like! Why not try an EFI system?
I finally have all the parts here to put together a YZ250 with Link (Atom) EFI ( transfer port injection ). Apart from the disadvantage of cost and weight there are a lot of advantages to be had with engine control.

[bucketracer]

Well I have to admit the motors output is everything I hoped for, and in all honesty what I expected.
The motor design was based on time angle area calculations. Time angle area sets the foundation for how well the motor will breathe and enables matching of port timings. Jennings proposed time angle area back in the early seventies (possibly earlier) but missed blowdown area. The concept of blowdown area was introduced by Blair, at least it was Blairs book "design and simulation of 2 stroke engines" that brought this to my attention. The first dyno run with the KERS was done with a reserved inlet timing in the hope of adding some midrange punch that would benefit kart track racing, it didnt! So I went back to the maths and set the timing to match the other ports. The calculations used for this motor suggested 32 crank hp at 11k, I assumed 15% loses which would be 27.2 rear wheel hp and we have 27.3 at 11.5k.
Of course its not as simple as just time angle area. We are incredibly fortunate with the internet age to have access to fantastic 2 stroke minds such as Jan Thiel, Frits Overmars, Wobbly, etc, etc and of course all the learnings of the ESE boys made available through the epic ESE thread. With the input and advice of these fantastic people it becomes possible for almost anyone to modify something as basic as a farm bike into a (modestly) high power 2 stroke motor. A dyno and an experienced operator helps too ;).
Big thanks to everyone that has helped both directly and indirectly to deliver this motor, especially TZ350 :drinknsin: Now to get it on to the track :woohoo:

A real testament to the intelligent use of Google and the Internet.

[TZ350]

279724
Can anyone explain what the part inside the pipe is.


When unleaded became mandatory in 98 most teams had a hell of a time keeping deto under control, having to run very rich and retarded.

The cylinders with the straighter pipes always gave alot more grief, untill a lowly dyno operator at Yamaha discovered that when he stuck a large pressure probe into the header, the deto went away.

They managed to keep this secret for a couple of years but when teams like WCM got hold of the bikes, and left pipes lying,word soon got around.

The "things " intruding into the header take varying forms,but all do the same thing - the usually bottom "bent "pipes dont have the same issue, so dont need the so called deto buttons.


I am not running unleaded, but I will keep the idea of a deto button in mind.

[TZ350]

Some of Blairs thoughts on the important features in an expansion chamber.

272017

I have been wondering about the static working pressure inside an expansion chamber but I did not see the answer there that I am looking for.

Clearly in a well tuned engine the pipe is at the right internal working pressure around peak torque, but does it continue to build up as the revs climb? And if it builds up, is high internal pipe pressure one of the things that stifles the torque curve on over rev.

Certainly reducing the pipes internal pressure on low throttle openings is a good way to avoid detonation during overrun into a corner or just trickling around the track.

So now the big question is, can we also get more over rev by moderating the working pressure in the expansion chamber?

This was some of my early thoughts that led to making the pipe blead system that I hope to try out next week.

[TZ350]

I know that maintaining a working pressure inside the pipe is important and that to much pressure will overheat the piston. I know it’s controlled by the stinger/nozzle dimensions but I don't understand the actual function of this internal pipe pressure. I would love to know more about what it does and how and why, if anyone can enlighten me I would be grateful.

[TZ350]

Recently I have been trying to find the posts that talk about pipes and collate and edit them. There is heaps of it and pages 620 630 640 650 660 670 680 690 700 and 730 have un edited collections of raw material. If your interested in expansion chambers they are worth a look. Pages 710 and 720 talk about crankcase volume and inlet length.

P574


One thing you wont get is deto of the end gases without loosing power.
The phenomenon of deto is caused by temp/pressure creating free radicals,this process eliminates a huge amount of the available energy in the combustion fuel.
And once the radiacals are formed, they are self sustaining,and cause a runaway reaction process - consuming more energy.
This is exactly why the egt drops when you are too lean, and deto starts - no energy left to create heat - ie no power.


It is the exhaust pipe that is doing 75% of the sucking, provided that there is combustion....


Thanks for the information, I guess with that being said, a Lambda probe is (can be) useful when step testing only.

I looked up Exhaust Gas Technologies on ebay, but found that there are many different probes by that seller there. Are the exposed tip high speed probes all the same and the only difference is the connector and the probe diameter (.25 & .187 in)? My gauge uses K-type thermocouples and no connector, the cables are clamped directly to the gauge. So is this the right probe for me? Or are there any better probes by EGT (faster, more durable, cheaper etc)?


A normal car-type Lambda probe lags only about 0.1 sec; that's fine for inertial testing.


That K probe is the good one,is fast and reliable and cheap.

P580


Thanks for the flowers, RAW.
You can have an intake length that is too short in combination with intake diameter, intake timing, crankcase volume and desired rpm, in which case the engine will express its displeasure by blowing back some of the inhaled mixture. I prefer to shorten the intake length as much as possible and shorten the intake timing accordingly.
By varying intake length, intake timing or crankcase volume you can adapt the induction system to different rpms. I think the best way to adapt to low revs is to advance the intake closing; it will make for a docile engine with a clean, easy to set carburation.

Varying exhaust pipe length seems to be a far better way of increasing overrev than retarding the ignition or leaning out the mixture; it would be a waste not to utilize all inhaled oxygen. Varying the pipe length can also markedly lower the beginning of the power band.


With a variable header length you do not need to artificially raise the exhaust gas temperature, so you need neither the power jet nor the ignition retard.
The 50 cc engine with trombone pipe that I wrote about some time ago, runs strongly from 7,000 to 17,000 rpm without power jet and ignition retard.

Note: the power jet in the Aprilia RSW / RSA is gradually closed and the ignition is gradually retarded till 10° before TDC. These engines rev to 14,500 rpm. But I am convinced that with a trombone pipe they would function much better still.


I am very taken with the Trombones possibilities and after using EngMod2T to simulate it, it looks like the Trombone is much better at extending a pipes upper range than plumping up the lower part of the torque curve below the pipes natural operating point.

So if you have an engine with a pipe good for 13K and a mechanical limit of 14 then its not much point in making a 13K trombone that can run 6K from 12 to 18.

After looking at the EngMod simulation results I think it makes better sense to discard my 13K pipe and design a pipe that’s a strong torque monster at 8K with the trombone effect extending its range out 6K to the engines 14K limit.

A trombone and power valve combination would be even better.


...if you have trial riding in mind...
A (partly) closed powervalve will spoil the exhaust pulse and exclude true 180°-resonance, so you will never get a decent torque value.
I think the trombone alone will be a better choice. It will be easier to realize as well. Remember: KISS.


Simple answer re the odd shape and reduced area of the Ex duct exit is that with a 3 port cylinder, the area of the main port is plenty big enough to support the gas flow
created by the power being made.
The big Aux additional area allows better Blowdown STA, but this area is only needed above TRO.
Thus having a huge duct simply drops the velocity, reducing the wave amplitude into the header.
The Aprilia shape promotes the flow from the Aux ports by keeping the extra horizontal area all the way into the pipe - thus helping blowdown flow and overev power..
Reducing the duct vol by having area reducing steps, keeps the velocity high and again promotes the flow regime in the side ports.
There may be a case to say that the steps reduce backflow from the pipe at low rpm when it is too short,but for sure there is no outflow disruption,and in any case tests showed that power went up as the duct became smaller.
I have exhaustively ( pun ) tested the vol/shape effects on a T port ( as has Mr H ) and an oval to round transition with no steps works better.
A factory A Kit has a very small 41 by 32 oval, with a CNC transition into a 41 header.

P596


I believe the big radius at the bore centre line has two effects.
Firstly is to improve the bulk blowdown flow at low opening angles of the piston controlled port orifice, due to the gas attaching early to the roof.
Secondly the exiting wave amplitude is lowered and smoothed out by the gradual ( instead of a sharp edge ) port opening.
This would improve the scavenging action bandwidth, but the peak value is probably then raised as well,simply because the port opens earlier when the pressure above the piston is greater.
Thus you get the best of both, a wider effective scavenging action, combined with a higher peak value, making the pipe work better over a wider range.

The big radius can only be applied to a port with the chrome removed, it then has to be replated to permit the ring to run on a hard surface as it bulges out into the port - unless of course you have an iron bore..


Only Yamaha stuck with the wank flat roof scenario way after the use by date, and got their arses kicked for years in GP.
Till they finally bought a CNC controlled Jante machine from Czech, went square bore/stroke and using the 500 cylinders on the 250 easily won the champs in 2000 with Olivier Jaques.

The secondarys facing each other relatively flat will always collide, but the hooks rotate the flow under the boost as it exits the port ( easy to see with the tap water Jante trick),clearing out a big "dead" area
in front of the rear port.

All modern race engines have a nozzle restriction at the flange face, as big T ports and tripple Exhausts loose alot of velocity going into the header.
Rule of thumb is a 75% of the effective EX area at the flange.
Stepped oval duct into a round flange does work, but I have used a CNC oval to round transition in the spigot for years, as has Honda in A kit, and Aprilia factory engines, this works way better.
Here is a sim showing my new 400cc F3 engine, with and without the spigot nozzle.

The stinger nozzle effectively removes the stinger tube length from the equation - it was developed for Spencers NSR that had one stinger 150 long, the other was 450.
The nozzle is around 2 to 3mm smaller than the tube stinger .


Yea but Lozza was it a R3,5 and was the port at 70 + % and did it pull 14500,or even closer to the moon.

The curved convex shape of the Aprilia duct corresponds directly with the area increasing due to the Aux ducts entering the main.
Again the idea is to keep the duct volume down.

The 75% area at the cylinder exit is just something I discovered after running hundreds of sims, most of them worked best with an oval to round transition in the flange that started with this area
and the pipe header diameter equalled the total effective area of the ports.
Its been tested and proven so many times now, by so many other people, that it should be the first mod to make to any T or tripple port engine.
Here is a pic of one I have just done, that happened to have a tapered spigot - enabling the Aux ducts to be run all the way down into the pipe.
Check the big rad on the transfer duct/bore edge.


The only difference is the end cone restrictor diameter: it's 23.3 mm for the 102 and 23.0 mm for the 106 (or the other way around; I can never remember which is which). One was for the 125 cc and the other was for the 250. As the 125 is on full song for a much greater part of the track than the 250, the restrictor difference should compensate for the EGT build-up. Personally I would never go below 23.3 mm with that kind of horsepower.

Thanks for the warning. Aprilia switched from NGK to Denso because parts of the isolator fell into the cylinder. Now they have switched to Superbikes .


I did a huge testing project a few years ago on Honda CR125 for SKUSA box stock racing in karts.
22mm was as small as I could go sitting dead on 40 Hp at the gearbox,going lower made it finicky to tuning and made no more power - 22.5 made less power.
Although the pipe is a tech item I was able to hide a "tailpipe nozzle " easily enough for testing and racing.

But also from experience that is about the limit on power and tailpipe nozzle size in all sorts of applications.


Wob, I have a question about EngMod results, if you have some time to spare.
I remember your comment about 'silly long headers'. I have the following and a 61X54.5 engine, which in sim is around 47hp (even at 0.83Ceff), but dynoed only to 34.5hp.

All the other parameters seem to be realistic, according to your guidance. I wonder whether this pipe could create a simulation over-prediction.
The thing is, I know neither the AFR nor the ADV curve, but the person to tune it on the dyno is supposed to have experience with these engines.

Furthermore, could you point out a few things, that a novice tuner should pay extra attention when assembling an engine, so that it's done correctly -like tolerances or similar things (??) ?


The pipe does indeed have a silly header, but the angle is close to what the second stage of a 2 stage header would have.
It then extends into what would normally be a shallow first diffuser cone.
The result is that the main diffuser is pretty steep, so its this that is giving the good depression around BDC - and the reasonable power delivery at that rpm.
The Aux ports are giving good blowdown , as there is only a small pressure rise when the transfers open.
So many small details affect the real power delivery, and I would have to write a book with 30 chapters to even begin to point you in the right direction
as far as correct assembly is concerned - and its this, that my customers are paying for.

P598


I have just completed a back to back test on the Ex port radius in a TM 125 kart engine. The cylinder from the factory was a special "tuned "expensive part number, and I was given a stock one to modify. For sure the two were very different, the stock one being alot lower timing. This was fortuitous,in that it enabled alot of room to be used to move ports.

First test was the stock cylinder with the main EX at 194, I put a big radius on the roof giving effective timing at 196.5 ( the trick cylinder was the same at 196.5 )
This instantly picked up power everywhere from 8000 to 14000, with alot better overev power, being 6Hp up at 14000 The next test involved dropping the cylinder,removing the chrome and regrinding the ports to the reverse stagger layout. The A port being the lowest, to allow alot bigger Aux ports.
The main Ex port now opened around 192,with effective at 195 but the Aux opened at the same time, giving better blowdown area, as well as the flow enhancing radius on all 3 ports.

With the reverse stagger giving better transfer area ( as the B,C ports being high with alot of width compared to the previously high A port ) the engine now made 2 Hp or more than the factory trick cylinder but was now 8 Hp up at 14000 and gained 400 rpm of usable overev, as previously it dropped dead at 13800 on track. This setup proved to be quite insensitive to jetting and timing changes, allowing alot more static advance giving much better off corner power without killing revs as this would normally do. Thus the enhanced blowdown flow of the radius at low port openings,allowed those much lower timings to be used effectively, enhancing power everywhere, but most importantly in the overev,where blowdown is most needed.

Frits is right when he says that the Italian factories are 3 years behind,as they still havnt started to use much of the technology developed at Aprilia even now.


Jennings raised this in his 2 stroke tuners handbook way back when - 1973 to be precise

"As regards the exhaust port, a secondary function is served by providing a bevel,
and radiused edges, around the port window. There is a very considerably contraction of
flow through any sharp-edged orifice, and such orifices may be made effectively larger
by providing them with a rounded entry. Improvements in flow in the order of 30-
percent could be had were it possible to give the port window edges a radius of, say, ¼
inch. Unfortunately, to do this would mean advancing the point of exhaust-opening a like
amount, which in most engines would result in a very radical exhaust timing indeed. It
is, on the other hand, often possible to carve just such a radius at the sides of an exhaust
port - although it is questionable that this radius would be as effective as simply widening
the port to the same extent. The radius approach does have the advantage of leaving
intact much of the metal around the port, which can be important: Thick sections of metal
tend to equalize cylinder temperatures and prevent the kind of local distortion that is such
a potent cause of piston seizure."


the top radius was 3.5 mm; it was tangential to the exhaust duct roof, but not quite tangential to the cylinder bore; that would have been extremely difficult to produce. Instead the centre of the radius was offset a little to the inside of the bore. That raised the timing from 196° to 202° when the first glimpse of light became visible.


Here we go...

Jan Thiel, p44 Pit Lane RSA125 thread...

"The exhaust port had a radius at the top, but this was more for the flow and not to avoid ring clipping.
We never had problems with the piston rings, the central exhaust port was not so wide."

When i read this i though that a normal curved port roof doesnt really do much extra for flow, its more about controlling the exhaust pulses and saving rings, so to me it made sense that he could be talking about a horzintal radius which would definitely have a big impact on flow.

Frits Overmars, p47 Pit Lane RSA125thread...

"Exhaust 202°, A-transfers 130°, B- and C-transfers 132°."

fpayart, p7 Pit Lane RSA125 thread Part 2...

Q: Will you tell us the final width and height of the RSA exhaust exit? (after some conversation regarding port widths)

A: The sizes are 39.5 width x 27.5 height (without the radius).
Now I can imagine your next request
The opening time is 196 ° measured without taking into account the radius.

To me this last bit sealed the deal... why would he give a height or a duration to the lower point on a normal curved roof radius (ie. the height to some point near the far side of the port roof)... he wouldnt, it doesnt make sense... i think think this adds further weight to the fact that its a horizontal radius blending inwards into the exhaust duct. This would explain the difference in durations listed by people who definitely know this engine. I guess the way the port acts is somewhere between the two durations, most likely determined by the exact dimensions or construction of the radius...

Also there is this...
Havent really read the detail but the pics reflect what i found on the RM250...
http://www.google.com/patents?id=ikswAAAAEBAJ&pg=PA2&source=gbs_selected_pages&cad=4#v=onepage&q&f=false


The port in the cylinder casting has a timing of 196°. Then the upper edge receives a radius that lifts the timing edge to 202°. It's as simple as that.


Yes, a deliberately rounded edge to the top of the port at the cylinder wall. Gas flows differently at different speeds, it'll follow the curve at some velocities, not at others. You can use this to effectively alter port timing over the rev range.

Page 600


Page 600 B

It seems that at high rpm and part throttle the pressure in the cylinder is higher than in the crankcase when the transfers open and hot burnt combustion gases back flow down the transfers.

Part throttle detonation is the current big issue for our 30+hp aircooled engine. Retarding the ignition on part throttle is only part of the solution.

More blowdown time area is required to lower the in cylinder pressure so opening the power valve further when closing the throttle at high rpm could be a solution.

Or the pressure inside the expansion chamber (and cylinder) could be lowered by having a second stinger pipe with a butterfly. Which is opened in high rpm part, throttle situations to drop the expansion chamber and cylinders working pressure.

And Frits proposes an idea where the intensity of the reflected wave is reduced by changing the size of the bleed venture at the end of the reflective cone.

Page 606


I believe the big radius at the bore centre line has two effects.
Firstly is to improve the bulk blowdown flow at low opening angles of the piston controlled port orifice, due to the gas attaching early to the roof.
Secondly the exiting wave amplitude is lowered and smoothed out by the gradual ( instead of a sharp edge ) port opening.
This would improve the scavenging action bandwidth, but the peak value is probably then raised as well,simply because the port opens earlier when the pressure above the piston is greater.
Thus you get the best of both, a wider effective scavenging action, combined with a higher peak value, making the pipe work better over a wider range.

The big radius can only be applied to a port with the chrome removed, it then has to be replated to permit the ring to run on a hard surface as it bulges out into the port - unless of course you have an iron bore..

Page 607


In all the engines I have done the area at the flange face is approx equal to the main port effective area, or approx .75 of all 3 ports. The header diameter is equal to the effective total of all three ports.

Page 610


The only difference is the end cone restrictor diameter: it's 23.3 mm for the 102 and 23.0 mm for the 106 (or the other way around; I can never remember which is which). One was for the 125 cc and the other was for the 250. As the 125 is on full song for a much greater part of the track than the 250, the restrictor difference should compensate for the EGT build-up. Personally I would never go below 23.3 mm with that kind of horsepower.

Thanks for the warning. Aprilia switched from NGK to Denso because parts of the isolator fell into the cylinder. Now they have switched to Superbikes .


I think the 102 has 23.3 restriction, based on the schematic in your files, Frits.


Have to reduce the Aprilia power output to down around 40 Hp to fit a 22.3 nozzle Frits.


Wob, are you saying you put that in engmod and got det warning when going higher then 40 hp when using 22.3 mm?


I did a huge testing project a few years ago on Honda CR125 for SKUSA box stock racing in karts.
22mm was as small as I could go sitting dead on 40 Hp at the gearbox,going lower made it finicky to tuning and made no more power - 22.5 made less power.
Although the pipe is a tech item I was able to hide a "tailpipe nozzle " easily enough for testing and racing.

But also from experience that is about the limit on power and tailpipe nozzle size in all sorts of applications.


The pipe does indeed have a silly header, but the angle is close to what the second stage of a 2 stage header would have.
It then extends into what would normally be a shallow first diffuser cone.
The result is that the main diffuser is pretty steep, so its this that is giving the good depression around BDC - and the reasonable power delivery at that rpm.
The Aux ports are giving good blowdown , as there is only a small pressure rise when the transfers open.
So many small details affect the real power delivery, and I would have to write a book with 30 chapters to even begin to point you in the right direction
as far as correct assembly is concerned - and its this, that my customers are paying for.

Page 613




I have just received another Knock Gauge, this one has two extra outputs. http://www.knockgauge.eu/content/blogcategory/22/41/

YouTube links showing the Knock Gauge in action.

The two green lights, the orange warning light then you see the red det light. http://youtu.be/aZkZR-JBr_E and http://youtu.be/vFoZyw_sHmA

Like last time, one that goes to ground for signalling the IgniTec to retard and a new one that pulses from 0V to +5V each time the Knock Gauge sees a detonation event.

The Curtis event counter can then count the detonations. Now I have the makings of a det sensor, ignition retarder and det counter.



This post links back to various cheap counters that could be used with the Knock Gauge.

Page 616


Running a KT100 is fraught with heat problems, as it affects every part of the testing.
Simply put, you MUST have the same head temp and case temp at the start of every test.
Then monitor the egt at the end of each test.
For example you can change the pipe length, run up the engine to get your reference head and case temp.
But the egt at peak rpm may be 100* lower.
So you must then turn the tap and change the jetting.
This then means repeat the test, until you reach the same egt as previously.
Then overlay the curves to see if the new pipe length actually is better than the last one.
All you are doing is replicating what would happen on the track,but making very sure the conditions are perfectly equal.
This enables the 1/10 Hp resolution in changes to be seen with confidence, as head or case or egt temp has a way bigger influence on the dyno power reading, than any pipe or small port timing change would ever produce.

Same issue with a water cooled 125.
If the change produces a change in egt, then you must go back and rejet and rerun the test.
On track we will always be shooting for a reference egt,by changing jets based on the current air conditions,no matter what the port timing or the ignition curve or the pipe shape,may be.
So the dyno result must reflect this process to be able to document on track reality and thus performance, with any useful accuracy.

P624


The pipe is a complete mess both % wise and taper wise - not even close to being too steep - as an Aprilia pipe is 124 or so diameter.
And expecting an engine to make serious power up at 14,000 with a 196 Ex port is a "pipe "dream.
The dip in power is due to a big mismatch in spec,that is synergistic at some points , but self cancelling at others.

P625


Some of Blairs thoughts on the important features in an expansion chamber.

I have been wondering about the static working pressure inside an expansion chamber but I did not see the answer there that I am looking for.

Clearly in a well tuned engine the pipe is at the right internal working pressure around peak torque, but does it continue to build up as the revs climb? And if it builds up, is high internal pipe pressure one of the things that stifles the torque curve on over rev.

Certainly reducing the pipes internal pressure on low throttle openings is a good way to avoid detonation during overrun into a corner or just trickling around the track.

So now the big question is, can we also get more over rev by moderating the working pressure in the expansion chamber?

P627


You know very quickly if an aircooled is thermally limited.
The power fades very quickly, and can be seen even doing an all gear run on the inertia dyno.
I spent 6 months testing pipes for KT100, and it was easy to make around 20 Hp, but this would drop 2 secs a lap as soon as it got hot, ie 2 laps.
You had to wind in fuel to cool it - not make power.
I ended up searching for power band width, pumping up the bottom end and overev power, keeping the peak well suppressed to prevent the power fade from affecting lap times.
Ive sold over 2000 of those pipes now, and so far no one has bettered them on track.

P631


Unleaded fuel to make best power likes to be rich and have plenty of advance with low com.
Thus in general a shorter pipe would be needed, as you say due to the lower egt.
But as usual there is a fly in the ointment in that the FIM race fuel that needs gloves and a respirator, acts differently, and ends up with the same tuned length as was used with ELF124.
But the bulk pipe temp isn’t what the egt probe reads in the header, its the average temp and is alot lower overall.


Ok Wob, thank you. Is there a way of tricking EngMod into predicting the right rpm for top power, when using unleaded fuel? So far it seems to predict the rpm range as if the egt was around 650C.


The biggest thing to realise is that the pipe wall temp seems to work best in the 0 to 100*C range.
I use 50* for most engines running on Avgas.
This is a fudge that Neels hates but works very well.

P655

[Flettner]

http://i1056.photobucket.com/albums/t380/uniflow/IMG_0849_zpsca9d7448.jpg
http://i1056.photobucket.com/albums/t380/uniflow/IMG_0848_zpsff97e4e3.jpg

Put a ball valve in the head, uniflow charge, water cooled valve, independent timing ( can be changed on the fly ) , more transfer time area available ( no exhaust port in the cylinder wall ), cooler running piston. Note this valve has piston ring type seal, reacts to pressure as a piston ring would in a round bore. This is a crude welded version it would need ceramic or some trick to keep the heat out of the valve I think? Or not, perhaps water cooled would be enough.

[speedpro]

There's bound to be a reason why not, but, if you were going to a uniflow arrangement why not make the ball valve control intake which is nice and cool and have the ex ports in the cylinder. You could have all the blowdown you need easily and with modern electronics you could reasonably easily alter the rotary valve timing. Of course you'd still have to overcome all the old problems that have plagued rotary valves like sealing and dealing with combustion pressures while rotating. I envisage a twin cylinder with the cylinders side by side but facing opposite. Pistons rise and fall together, but in opposite directions, and each crankcase feeds the other cylinder rotary valve. Each rotary valve driven from the adjacent cylinder's crankshaft and a gear train between the cylinders with power takeoff anywhere handy.

[Flettner]

Picture please.

[Frits Overmars]

Put a ball valve in the head, uniflow charge, water cooled valve, independent timing ( can be changed on the fly ) , more transfer time area available ( no exhaust port in the cylinder wall ), cooler running piston.Been there, done that, 30 years ago. Well, almost; while a friend of mine, Alex Hofmann, built a four-stroke head with two hollow rotating ball valves (first picture),
I designed a cylinder head for a Yamaha TZ350 twin with a conical Aspin valve above each cylinder.
Each valve had two diametrically opposed windows that gave access to either the two exhaust ducts per cylinder head or the two spark plugs per cylinder head.
This symmetry made for a good balance of the valves but also necessitated that they rotated with half the crankshaft rpm. This in turn meant port opening was much too slow for a decent blowdown angle.area. I solved this problem by varying the valves' rotating speed: slow when the exhausts were fully open (BDC) or fully closed (TDC, with the advangage that compression and combustion forces did not cause so much friction losses) and fast in-between. This was accomplished with a train of noncircular gears between crankshaft and valves. All rather complicated; everything had to be lubricated as well.
Maybe now you'll understand better why I keep saying KISS: keep it simple, son.

[TZ350]

Changing ratational speed with non circular gears, now thats very clever .....

[Frits Overmars]

Changing ratational speed with non circular gears, now thats very clever .....Almost as clever as thinking a little longer and going for simple piston-controlled exhaust ports :p.

[Ocean1]

Changing ratational speed with non circular gears, now thats very clever .....

Is a very cute trick, eh? Not quite as easy as it might seem though, in theory the tooth profile changes as the radius does. I've got a wee plugin in a CAD app that generates the gears automatically, can't do the variable tooth profile though.

[TZ350]

I know that maintaining a working pressure inside the pipe is important and that to much pressure will overheat the piston. I know it’s controlled by the stinger/nozzle dimensions but I don't understand the actual function of this internal pipe pressure. I would love to know more about what it does and how and why, if anyone can enlighten me I would be grateful.

I feel I understand the sucking and plugging action of the dynamic pressure wave in an expansion chamber but I would be very interested in knowing more about the function of the static (or average) pressure system that exists in the pipe as defined by the stinger/nozzel pressure blead.

[Flettner]

http://i1056.photobucket.com/albums/t380/uniflow/c0231e31.jpg

Frits, thank you for answering my post. It's me ( uniflow ) If you remember, I'm responsible for this variable rotary valve housing. Don't worry I can take simple and make it complicated!
This ball valve has never been finished although one day I would like to try it. The key to it's potential success is the round piston ring that seals like a piston ring in a cylinder, seals on a round surface. Originally I was going to use oval gears like you have shown but then decided to occillate the valve. This gives you fast / slow and only one ring is required also the ring gap need never pass over the port. Ring gap would be at 90 degrees to the drive shaft. As you would I'm sure know uniflow offers clean combustion every cycle. Although my 440 uniflow engine ran well it was complicated and sooner or later ( as BMEP rose ) exhaust piston would be a thermal problem.

[chrisc]

I'm just going to put this (blasphemy?) here...
http://page.auctions.yahoo.co.jp/jp/auction/165511282

MD250 Moriwaki. Based on RS125 as sold by Honda with CRF150R engine instead of the 250 they otherwise come with

[Frits Overmars]

Frits, thank you for answering my post. It's me ( uniflow ) If you rememberI sure do. I'm just wondering now: should I address you as Flettner, as Uniflow or simply as Neil? In any case, I will take this opportunity to compliment you on your projects. The variable rotary valve housing is clever, I like your EFI, and your uniflow engine is impressive.


Don't worry I can take simple and make it complicated!You don't happen to have Italian roots, do you? :msn-wink:


This ball valve has never been finished although one day I would like to try it. The key to it's potential success is the round piston ring that seals like a piston ring in a cylinder, seals on a round surface. Originally I was going to use oval gears like you have shown but then decided to occillate the valve. This gives you fast / slow.Fast / slow is the direction to go, but for really turbulent-free flow you would need 'very fast / stop', with the channel through the ball in line with the stationary parts of the exhaust duct. But then the acceleration forces would become huge.
Maybe you could take another look at Alex Hofmanns four-stroke head; for each 'valve' he uses a hollow sphere that intersects the stationary duct; the part of the duct inside the sphere is also stationary; good for flow and for keeping heat away from the sphere.
Still, for uniflow I would prefer piston ports for both transfer and exhaust. But I have to agree that cooling the exhaust piston would require a brain wave.

[Yow Ling]

But I have to agree that cooling the exhaust piston would require a brain wave.

Would a sleeve valve work in this application?

[koba]

Maybe you could take another look at Alex Hofmanns four-stroke head

Thanks for posting this, it's really cool.

I spent ages dreaming up similar ideas when just out of school, I'm sure many of you are the same.
To actually see someone try and build on is very, very cool.

[koba]

But I have to agree that cooling the exhaust piston would require a brain wave.

It's not at all a brain wave but it would be much easier if using a wet sump on the exhaust sides, then the undersides if the pistons could be spayed with cooling oil; like in a lot of turbo engines.

Would one have to supercharge it then, or could one have a small 'starter charger' and completely forsake the crankcase pumping effect, relying entriely on the pipe action for running.
Feasible for a race engine?

This probably makes no sense at all.

Just thinking with keyboard in hand.

[Flettner]

My Kawasaki has a similar " chamber bleed " welded into it, accept mine is not a bleed, it's a pressure take off for the EFI system to help it make up it's mind on fueling. Seems to help because it fell off the other day at a trail ride. Straight away I could tell something had changed.

[dinamik2t]

Hey, Wob, could you give a little more info on how you do the ignition unit mapping with your ignition dyno?

279844

[wobbly]

In the pic you see the rotor mounting.
On the other end of the shaft I fit my large ( 400mm ) alloy protractor, with a stiff pointer set to 0/360 degrees, on the timing marks.
The vacuum cleaner motor has a light dimmer rheostat in the field winding, and with that and a small digital rev counter triggered off the plug lead,I video record the unit spinning up
slowly thru the rpm range.
I used to use a VHS video camera years ago, but the player died, so I had to buy digital camera that records onto a CD.
With a strobe shining on the degree marks as it spins, I can play back the video back on a big screen in slomo, watch the digital rpm gauge, and note down the change in timing every 100 rpm or whatever.
You can pause the recording as well to see the occasional wavering result.
At the end I go back around to the rotor end and strobe the timing marks to find out at what rpm the timing marks are aligned, and double check that the protractor is seeing zero at that rpm.
From the rpm/degree chart I can then add the calculated static timing to the curve.
If for example you run 1.4 mm static on a 125 this would add say 15* to the zero reading on the protractor,at the timing mark rpm seen on the strobed rotor.
This gives the actual timing the engine sees at every noted rpm.
Its also then easy to change the static timing, and draw the resulting new curve.
I have a standard calculation spread sheet that I simply fill in the angles,the static timing / rpm, stroke and rod length , and Mr Gates draws the graph for me.
Can you have the spreadsheet - no.
Im dumb, so i got one of the dumber PhD students I supervised at Uni to do it for me.

[dinamik2t]

Thanks for the morning class Wob :p

To be honest I know almost nothing on this topic. I am looking around the web in order to find info, but it seems I 'm not using the correct keywords.
I was thinking on calculating the RPM from the crank position sensor (reluctance) via software (I have a daq device) and find a way of calculating the advance from the cdi ignition signal.
Static advance is the easiest part I think, as it can be calculated from the rotor-pickup directly. The RPM signal must be easy too if you convert reluctance to digital. Main problem to me is how to measure the advance over RPM -strobe can't be the only way.

The objective is to map different CDI versions from 2 bikes-rotor specs (static advance is stated in the manual). So, I thought of cutting thick iron disks corresponding to the rotor diameters/lobes, in order to avoid mounting issues and to use a less powerful motor. Like the ones sold from Ignitech. (this way I can also keep a 'record' of those engines' rotors.) Would you think of any potential problem with this?

There is a guy here doing something that looks like mapping via oscilloscope & software: http://cbr250.com/forum/thread-11008-page-7.html ; but the topic is a little messy and I am a little dumb.

Anyway, thanks again Wob :drinknsin


p.s. doesn't your camera have a card slot, like SD or something? I hate CDs...<_<

[wobbly]

I bought the trick CD camera for a fortune when we still had VHS video cassettes, phones nowdays have better resolution.
As per the video all this is easy now with digital storage scopes and you can buy digital output rotary position sensors that have 360 pulses per rev.
With Matlab you can easily use the position sensor and a pulse from the coil wire, calculate the time delay from the rpm, and it will draw the graph for you, with an offset for the static setting.

[Forgi]

Hi Friends!

Wobbly! Do you have any logical explanation that in case of the simple exhaust port why the narrow exhaust nozzle did not work? If Engmod is right the 75% rule has to work, according to the simulations. What's more, I think that in case of a simple exhaust port a smaller exhaust nozzle can also work!

A simple trapezoid exhaust port with a chordal of 70-75% is almost the same like a not too wide T port, so from this point of view it also has to be work! I have just wanted to do some tests, if you are interested I'd share my results.

[TZ350]

A simple trapezoid exhaust port with a chordal of 70-75% is almost the same like a not too wide T port, so from this point of view it also has to be work! I have just wanted to do some tests, if you are interested I'd share my results.

I would be very interested in the results.

[wobbly]

The exhaust nozzle I believe when used with a big T port or a 3 port with plenty of blowdown area is doing two things.
Firstly it is reducing the volume of the duct, and secondly it is matching the flow capability ( or increasing velocity, depends on how you look at it ) of the duct to the actual
requirement of the power being made.
If you take the area of the main port and add the two eye ports, this dramatically increases the blowdown STA and thus the power potential.
But in reality this total area isnt needed for the power potential, its the blowdown that is important.
From doing hundreds of simulations and building more engines than I care to count, the best power is made by matching the header inlet area to the total Ex effective area, but reducing
the duct to around the 75% as mentioned.

But when you have a single Ex port, out at 72% or whatever, and lift it to the max at around 200+ duration, the power is ALWAYs limited by the blowdown STA available.
A simple trapezoid will never be able to match a T port for ultimate blowdown STA capability.
Thus having a limited power capability, we already have a matching small port and duct.
I have found in many cases that power will go up if the duct exit is made around 90% for things like a TZ350, that has a big port, but the bmep ,thus power, is fairly low.

As Frits has alluded to we should be matching the duct to the blowdown available, and this would give a much better approximation to the ideal duct exit needed.

[SwePatrick]

I sure do. I'm just wondering now: should I address you as Flettner, as Uniflow or simply as Neil? In any case, I will take this opportunity to compliment you on your projects. The variable rotary valve housing is clever, I like your EFI, and your uniflow engine is impressive.

You don't happen to have Italian roots, do you? :msn-wink:

Fast / slow is the direction to go, but for really turbulent-free flow you would need 'very fast / stop', with the channel through the ball in line with the stationary parts of the exhaust duct. But then the acceleration forces would become huge.
Maybe you could take another look at Alex Hofmanns four-stroke head; for each 'valve' he uses a hollow sphere that intersects the stationary duct; the part of the duct inside the sphere is also stationary; good for flow and for keeping heat away from the sphere.
Still, for uniflow I would prefer piston ports for both transfer and exhaust. But I have to agree that cooling the exhaust piston would require a brain wave.



Look at this video,, i think this is the way so solve some issues ;)
http://www.youtube.com/watch?v=Bch5B23_pu0&feature=youtu.be

[TZ350]

Deto in the Over Rev Zone.

279979

The mid chamber bleed.

279980

Tried it open and closed, Red open, Blue closed. The big surprise was how quiet it was when open, hardly any more noise at all, certainly wouldn't need any sort of mufler.

Actually I tried it lots to see if I could join the two curves and if it would kill the high rpm deto. But it was difficult to coordinate by hand and the runs were all over the place. Although the results were good enough to make me very interested in developing a proper ATAC Valve.

279978

Kel gave me a hand to try and figure out where this top end deto is coming from.

I tried to take pictures when the Red light flashed, but all I got was a lot of unfocused blurry photos.

Although I could see the Red light flashing, in all of the shots the green light obscured the Red deto one.

<iframe src="http://www.youtube.com/embed/TYMFOuigEf8" allowfullscreen="" frameborder="0" height="315" width="420"></iframe>

At the end of the runs the engine went into auto ignition and ran on, in the clip you can just see Kel pull in the clutch and thumb the kill button but the engine still ran on for a bit.

279981

Kel has suggested that the dings in the copper squish area left from an earlier blowup may be the problem.

Thanks to Kels help I now know that the deto is likely a part of the auto ignition problem. Changing the timing and/or jetting did not help.


(http://youtu.be/TYMFOuigEf8)

[koba]

279979

Tried it open and closed, Red open, Blue closed. The big surprise was how quiet it was when open, hardly any more noise at all, certainly wouldn't need any sort of mufler.




Interesting curves. :blip:

Maybe there is more to it but 'linking the curves' looks like a potential direction for progression.

[koba]

Kel has suggested that the dings in the copper squish area left from an earlier blowup may be the problem.



I'd certainly suspect that.


The video on the 'free valve system' was interesting.

I'd wondered why such a technology wasn't already in production, perhaps it isn't so far away.

[Bert]

Deto in the Over Rev Zone.

279979

The mid chamber bleed.

279981

Kel has suggested that the dings in the copper squish area left from an earlier blowup may be the problem.

[/URL]

Really interesting development Rob (should be easy to control the bleed with the ignitech).

I've been following this Deto thread with interest and often wandered if the copper squish area may be an area for concern.
two things that come to mind:
1. with likely expansion, is the squish (being copper sheet) expanding into the main combustion chamber; thus creating potential heat pockets (or sharp edges) which start the combustion process early (with the burning gasses not escaping cleanly).
2. is the copper sheet being lifted under compression (the photo eludes to it being out of shape); is there a possible limited life to the use of a thin copper sheet before it anerls (sp) itself to a point that it deforms under high temperature/pressure? again generating areas of heat pockets...
the reason for this thought is the only deto rings I've ever seen personally, (and other Fits & Wobbly will; I'm sure put me right) are quite solid (3-5mm thick); and machined into either the head or the top of the barrel.

two cents, probably only worth one.:niceone:

[Frits Overmars]

Look at this video, i think this is the way so solve some issues http://www.youtube.com/watch?v=Bch5B23_pu0&feature=youtu.beA very interesting video, Patrick; I enjoyed watching it. No bla bla sales talk, just facts. But I doubt that these oil pressure actuated valves will be useful for us.
I have seen similar valve actuation in a Lotus prototype engine and there I noticed the same points of attention that Christian von Koenigsegg mentions in the video.

First, the 2 ms delay in opening the valve. For an engine revving at 10,000 rpm that means a delay of 120 crank degrees... And no matter how fast the valve can be accelerated, it has to start moving from standstill; its initial velocity is zero. In my book that is a very slow rate of port opening, compared to a piston that is already at its maximum velocity when it starts opening an exhaust port.

Then there is the available port area. You can cram 2, 3, 4 or even more valves in a cylinder head, but the more valves you fit, the more they are in each other's way, especially when they all open at the same time.
If you leave valve acceleration forces aside for as moment and just concentrate on maximum flow area, one central exhaust valve in the head is optimal (its diameter should be cylinder bore / SQR(2) ). But even this optimal area, combined with the slow rate of opening, cannot match the angle.area of piston-controlled exhaust ports.

Then there is the rev limit. In the video a maximum of 20,000 rpm is mentioned, no doubt for the tiny valves of a high-revving four-valve four-stroke motorcycle engine. That means each of these small valves can open and close up to 10,000 times per minute.
But we are not dealing with four-strokes (at least I am not). In a two-stroke each valve has to open during each revolution. That means a maximum rpm of only 10,000 with these small valves. And if we go for the maximum flow area with a large central valve, that 10,000 rpm maximum will shrink to 8,000 (more mass and more lift).

Next: cooling. In a four-stroke the exhaust valves sit on their seats three-quarters of the time, dissipating heat. No such luxury in a two-stroke....

Summary: not enough angle.area, not enough revs and not enough cooling. If you really want to use valves, poppet valves won't do; look at rotating valves.
Or look a bit further and use piston ports :msn-wink:.

[wobbly]

The red open/blue closed curves has reminded me about your question regarding pressure in the chamber TeeZee.
A residual pressure in the chamber is, part of the dynamic supercharge effect of the wave action,increasing its bandwidth - as from PV=nrT when the pressure increases, so does the
gas density and the temp.
This dynamically varies the wave speed with rpm.

This effect is used in reverse with big champ jetski engines.
They use a big stinger, to DECREASE the pressure bleed, and thus the effective pipe wave action, at lower rpm, then squirt water into the stinger to squeeze its area down at high rpm.
Essentially returning the chamber to "normal " conditions as the rpm increases.

As you have found - decreasing the pipes negative effect on the scavenging at lower rpm ( because its too short ) is achieved by reducing the residual pressure in the pipe, thus reducing the temp/density and wave speed - seems counter intuitive to many who think you would need a smaller stinger to make the pipe work " better ".

There may be some truth to the other comments I have heard about pipe back pressure reducing the loop speed and thus short circuiting into the header, but I prefer the physics equation - seems more elegant.

[TZ350]

Really interesting development Rob (should be easy to control the bleed with the ignitech).


I am not sure the bleed did much for controlling the deto but it does suggest that an ATAC valve could be very worthwhile.


is the copper sheet being lifted under compression (the photo eludes to it being out of shape); is there a possible limited life to the use of a thin copper sheet before it anneals (sp) itself to a point that it deforms under high temperature/pressure? again generating areas of heat pockets...

279989

The copper forms the squish band, in the past its been very reliable and a good friend. But looking at the heat discoloration on the upper edge it looks like you may be right, the copper could have buckled and become a heat source.

But why is the deto only in the over rev zone and not peak torqe.

[TZ350]

The red open/blue closed curves has reminded me about your question regarding pressure in the chamber TeeZee.

Thanks Wob.

[Flettner]

Frits, The cooling of the exhaust piston in my uniflow engine was the most difficult problem. You can appciate that I wanted full cylinder exhaust ports all the way round the cylinder. In a standard 2T engine the piston at least gets cooling from the transfers around the rest of the piston away from the exhaust port, no such luxury on the uniflow. Under piston cooling is significant and is what is saving the uniflow piston. Because of the way the crankcases are both pumping into the same cylinder I was able to make one inlet ( under the transfer piston ) just induct air, the other intake ( under the exhaust piston ) induct air and twice the fuel, very rich mixture. It all mixed in the same cylinder anyway. This extra rich mixture under the exhaust piston made for a much safer engine. Also the exhaust piston is smaller than the inlet piston and flat top. This allowed for some squish in the combustion chamber. It would be nice to try also a different material for this exhaust piston, perhaps carbon / carbon.

[Haufen]

There may be some truth to the other comments I have heard about pipe back pressure reducing the loop speed and thus short circuiting into the header, but I prefer the physics equation - seems more elegant.

I don't know if the loop speed is reduced, but I know that a higher exhaust back pressure can influence the timing when the mass flow in the open transfers actually starts moving out of the ports.

Another effect of a higher back pressure is that the scavenging column has a higher resistance to overcome to short circuit out of the exhaust port.

In combination with exhaust pipes, higher back pressure reduces the suction on the transfers / crankcase, but increases the amplitude of the returning stuffing pulse.

[speedpro]

But why is the deto only in the over rev zone and not peak torqe.

Pretty sure there's been a few good theories about that from people who should know. My favourite is something along the line that at peak torque everything is being very efficient - exhaust out, fresh mixture in, squish, bang, repeat. There is minimal mixing of burnt gas and fresh mixture. In over rev, there isn't enough time for the burnt gas to exit and when the transfers open the pressure differential causes a momentary flow of hot burnt gases into the transfer ducts. The transfer ducts now have a combination of hot exhaust gas and fresh mixture in them which is then transferred into the cylinder. This mixture apart from being warmer than a nice clean fresh fuel/air mix also has a different chemical composition. In a methanol fueled engine this diluted fuel/air mixture has a significantly lower octane rating, so I've been told. I assume it's similar for petrol. Anyway, it starts out warmer and then gets compressed as usual and as a result of Boyles law gets to the point where it auto-ignites before the spark. This ignition event is early, advanced, which in conjunction with the lower octane rating of the diluted mixture also could result in detonation. No happy happy joy joy there I'm afraid.

That's my take on it.

A design that would help with this I would have thought would be a bridged ex port, or triple port, with lots of blowdown T/A and low and wide transfers. The low wide transfers will give the required T/A and the greatest blowdown T/A, for any exhaust T/A, which will reduce the mixing of exhaust and fresh mixture. This might be why proper race cylinders didn't seem to have such an issue with over rev deto. Riding styles and tracks contributed as well I think. Little power valves in the transfers might help by increasing blowdown T/A but would of course lower transfer T/A which may not be too much of a problem. They might be useful in the situation where revs are up and at smaller throttle openings where deto is also a problem.

[husaberg]

Pretty sure there's been a few good theories about that from people who should know. My favourite is something along the line that at peak torque everything is being very efficient - exhaust out, fresh mixture in, squish, bang, repeat. There is minimal mixing of burnt gas and fresh mixture. In over rev, there isn't enough time for the burnt gas to exit and when the transfers open the pressure differential causes a momentary flow of hot burnt gases into the transfer ducts. The transfer ducts now have a combination of hot exhaust gas and fresh mixture in them which is then transferred into the cylinder. This mixture apart from being warmer than a nice clean fresh fuel/air mix also has a different chemical composition. In a methanol fueled engine this diluted fuel/air mixture has a significantly lower octane rating, so I've been told. I assume it's similar for petrol. Anyway, it starts out warmer and then gets compressed as usual and as a result of Boyles law gets to the point where it auto-ignites before the spark. This ignition event is early, advanced, which in conjunction with the lower octane rating of the diluted mixture also could result in detonation. No happy happy joy joy there I'm afraid.

That's my take on it.

A design that would help with this I would have thought would be a bridged ex port, or triple port, with lots of blowdown T/A and low and wide transfers. The low wide transfers will give the required T/A and the greatest blowdown T/A, for any exhaust T/A, which will reduce the mixing of exhaust and fresh mixture. This might be why proper race cylinders didn't seem to have such an issue with over rev deto. Riding styles and tracks contributed as well I think. Little power valves in the transfers might help by increasing blowdown T/A but would of course lower transfer T/A which may not be too much of a problem. They might be useful in the situation where revs are up and at smaller throttle openings where deto is also a problem.

Just an observation
<img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=275139&d=1356561165" width="240px"/><img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=277747&d=1359748275" width="240px"/><img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=279999&stc=1&thumb=1&d=1363346075" width="240px"/> <img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=280000&d=1363346102" width="240px"/>
The devil is in the detail as it were.Shape EX Aux EX and A ports under AUX

<img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=275269&d=1356723808" width="240px"/><img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=275266&d=1356723798" width="240px"/><img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=280003&d=1363349482" width="220px"/><img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=280001&d=1363348854" width="240px"/>
I also have a suspicion the shape of your septums may be a little out of kilter ( referring to the to the direction)front and rear wall of the trensfers too.
but can't be arsed looking for the pics.(ok i could)
Ignore the pointer not what i am talking about

Note this detail is impossible to normally see in most pics. I will call it slant for lack of a better term.


Frits also alluded to lowering the comp for more over rev perhap's he or Wob could be kind enough to expand on it

[Frits Overmars]

Frits alluded to lowering the comp for more over rev perhap's he or Wob could be kind enough to expand on itJudging from the way you wrote that word expand in italic, you have a pretty good idea yourself, Husa. A lower compression ratio before TDC equals a lower expansion ratio after TDC. That means a smaller temperature drop in the burnt gas during expansion, hence a higher exhaust gas temperature, a higher speed of sound in the gas and a higher resonance frequency in the pipe.

[husaberg]

Judging from the way you wrote that word expand in italic, you have a pretty good idea yourself, Husa. A lower compression ratio before TDC equals a lower expansion ratio after TDC. That means a smaller temperature drop in the burnt gas during expansion, hence a higher exhaust gas temperature, a higher speed of sound in the gas and a higher resonance frequency in the pipe.

Oh Frits But i would not have been so concise or eloquent though.
The Aprilia was still fairly high. I think either you or Jan wrote is was always generally 16:1 or similar is that right?
Did this vary say higher tight tracks lower open tracks, or was the comp just optimised for the best hp/acceration/over rev compromise at the circuit.

I remember the Poloni power head From Robinsons book did anyone ever use it in competition

Is there anything in the other bits i observed or have i drifted off on a tangent?

[Frits Overmars]

...The Aprilia was still fairly high. I think either you or Jan wrote is was always generally 16:1 or similar is that right? Did this vary say higher tight tracks lower open tracks, or was the comp just optimised for the best hp/acceration/over rev compromise at the circuit.The compression ratio was always between 15.5 and 16, optimized on the test bench. No adaption to weather, tracks etc. At least not officially; what individual mechanics got up to, was beyond control. But such actions certainly were not recommended.


I remember the Poloni power head From Robinsons book did anyone ever use it in competition?Not at Aprilia. I seem to remember that Team Roberts once tried variable comp heads on the factory Yamaha 500s, but the name Poloni does not ring a bell.

[husaberg]

The compression ratio was always between 15.5 and 16, optimized on the test bench. No adaption to weather, tracks etc. At least not officially; what individual mechanics got up to, was beyond control. But such actions certainly were not recommended.

Not at Aprilia. I seem to remember that Team Roberts once tried variable comp heads on the factory Yamaha 500s, but the name Poloni does not ring a bell.

I spelt it wrong too i guess "Polini" powerhead

http://www.kpmotosolutions.com/img041.jpg

[bucketracer]

I don't believe you. more than the 22 HP, Post the results. Oh, and I want to see a video of it on the dyno as well (just in case someone "pads" the results).....

Plenty of posts and video's on this thread, use "Thread Tools" then "View Thread Images" to find them.

You can also sort them 70 to a page from the begining or end, easy to troll through them and find what your looking for and other interesting posts.

[2T Institute]

The compression ratio was always between 15.5 and 16, optimized on the test bench. No adaption to weather, tracks etc. At least not officially; what individual mechanics got up to, was beyond control. But such actions certainly were not recommended.

Not at Aprilia. I seem to remember that Team Roberts once tried variable comp heads on the factory Yamaha 500s, but the name Poloni does not ring a bell.

Compression was varied with the track and weather..........well that's what I was told anyway:wacko: Having now started to use 118mm rods in a 125 we are finding really odd things like the engine demands to be run rich with black wash patterns on the piston(like some GP pics I have seen) and ignition seems to be less of a influence. Good points are torque band is getting higher and wider.

[husaberg]

Having now started to use 118mm rods in a 125 we are finding really odd things like the engine demands to be run rich with black wash patterns on the piston(like some GP pics I have seen) and ignition seems to be less of a influence. Good points are torque band is getting higher and wider.

No time to dwelling on the Why?;)

[TZ350]

http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=275269&d=1356723808http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=275266&d=1356723798
I have a suspicion the shape of your septums may be a little out of kilter ( referring to the to the direction)front and rear wall of the trensfers too.

280014280015

Looking at the Rotax drawring and my piston, I think your right. I am in the process of making another cylinder and will be using better tools so hopefully a better result.

280016

That old cylinder made 30hp, if I can fatten up the lower part of the torque curve with better direction from the transfer ports I will be very happy.

[Frits Overmars]

Looking at the Rotax drawring and my piston, I think your right. I am in the process of making another cylinder and will be using better tools so hopefully a better result.
That old cylinder made 30hp, if I can fatten up the lower part of the torque curve with better direction from the transfer ports I will be very happy.That Rotax drawing (it's not from Rotax; I drew it in 1980) shows the original Rotax 124-cylinder of that time. Next I rotated the trailing flanks of the B-ports 15° towards the exhaust side (I would have liked to do more but then I would have struck coolant), fitted a 38 mm Mikuni and a fat pipe (official Rotax pipes then measured 100 mm at the belly; mine was 128 mm) and measured 34,5 HP/12,500 rpm at the chain. A flat tire cost us the title in the European kart championship. Life is hard.....

[breezy]

yeah went for the rotax barrel myself, had an mtx 125 in mind originally( with my gp 125 crank ,i have inside 50.6x 56) just got to have the barrel skimmed down 5mm and get a thicker bottom barrel spacer(20mm thick)..

[Frits Overmars]

yeah went for the rotax barrel myself, had an mtx 125 in mind originally( with my gp 125 crank ,i have inside 50.6x 56) just got to have the barrel skimmed down 5mm and get a thicker bottom barrel spacer(20mm thick)..If you are going to use the Rotax cylinder in the above picture, the most important thing to watch is the coolant passages alongside the exhaust duct. Chances are that they are partly or even completely blocked by casting skin. The picture below shows an undersized coolant passage left (in the yellow circle) and a completely blocked passage right. If this is not rectified, it may kill your engine the first time you give it some stick.

[Forgi]

The exhaust nozzle I believe when used with a big T port or a 3 port with plenty of blowdown area is doing two things.............

Ok Teezee, once I get the results I'll share them!

Wobbly, I think I understand what you are saying, but lets see an example, right?
Look at this picture, this way it'll be easier to understand!

70cc 45/44 bore/stroke

http://kepfeltoltes.hu/130317/w_www.kepfeltoltes.hu_.jpg

As you can see the effective area and the STA of the two exhaust ports are the same, only the angles are different. It is easy to understand that up to a certain RPM you can't use a simple exhaust port to make an STA like this, without increasing the angle. (However in this case it doesn't matter.)

In theory 193 degrees could be the better because of the resonance in the exhaust. Frits has already talked about this. (190ex./130tr.)

What do you think? Although every pharameters are the same the tight nozzle couldn't work?

If it is true isn't it possible that in case of a simple port the nozzle has to be smaller than 75%? It would be logical cause if we take into account the proportions the blowdown area is smaller than the exhaust effective area in case of a T-port or having 3 ports. (of course the example above is not that case :-))

[2T Institute]

No time to dwelling on the Why?;)

Thought of that but doesn't explain what we have experienced

[husaberg]

Thought of that but doesn't explain what we have experienced

Good points are torque band is getting higher and wider.

Having now started to use 118mm rods in a 125 .... Good points are torque band is getting higher and wider.

[wobbly]

The problem here is that both examples you have given i would never work with.
Any 70 cc RACING engine at 10,000 rpm isnt even into the powerband, let alone pushing the limits of power with those timings.
All the work I have done is with full noise designs that are pushing the limits of what can be achieved in every area I can modify.
Trying to use my guide of making the header equal to the total Ex effective area, and making the duct nozzle = 75%, in an engine that wont make any power anyway, is
missing the point entirely.

[breezy]

If you are going to use the Rotax cylinder in the above picture, the most important thing to watch is the coolant passages alongside the exhaust duct. Chances are that they are partly or even completely blocked by casting skin. The picture below shows an undersized coolant passage left (in the yellow circle) and a completely blocked passage right. If this is not rectified, it may kill your engine the first time you give it some stick.

thank you very much for the info,ill take a look

[wobbly]

Rotax did the exact same error on the 257 single road race cylinder, many had no hole on one side and a small 3mm triangle for all of the water flow on the other side.
Dumb - about as good as the non existent QC on big end rollers, I used to buy 20 big end bearing kits, and measure every roller into +/- 1 micron diameter sets.
Some kits had 1 roller 5 microns bigger than all the rest - instant failure waiting to happen with no recourse on the wankers at the factory.

[koba]

Some kits had 1 roller 5 microns bigger than all the rest - instant failure waiting to happen with no recourse on the wankers at the factory.


Maybe that's what they were doing rather than QCing.

"Hans, pass the grease..."

[TZ350]

I am looking at trying my hand at fuel injection and would like to know how that fits with the "equivalent to a single 24mm carb" rule.

280087

Is a 24mm venturie inlet and injectors in the engine some place equivalent to a 24mm carb??

[Frits Overmars]

Forget that 6° diffuser opening angle, TeeZee. That would be fine for continuous flow but what you have in your engine, is pulsating flow and there the main flow resistance is caused by having to accelerate the mass of mixture in the inlet tract at every turn. So keeping that tract as short as possible is much more important than having a turbulence-free diffuser angle.

[husaberg]

24mm throttle body seems fine to me EQ to a single 24mm carb i recall

[Flettner]

Much better to run a drum type throttle. You need a TPS and an in cable type liner type won't work well. Best it to have the TPS connected direct to the throttle shaft. Butterflies are not good in a twostroke inlet.
http://mob1056.photobucket.com/albums/t380/uniflow/IMG_0523_zps0178bbce.jpg?t=1356511362
http://mob1056.photobucket.com/albums/t380/uniflow/IMG_0522_zpsce09d679.jpg?t=1356511471

[Flettner]

http://mob1056.photobucket.com/albums/t380/uniflow/IMG_0490.jpg

http://mob1056.photobucket.com/albums/t380/uniflow/IMG_0488.jpg?t=1356511565

http://mob1056.photobucket.com/albums/t380/uniflow/IMG_0489.jpg

[husaberg]

Much better to run a drum type throttle. You need a TPS and an in cable type liner type won't work well. Best it to have the TPS connected direct to the throttle shaft. Butterflies are not good in a twostroke inlet.
http://mob1056.photobucket.com/albums/t380/uniflow/IMG_0523_zps0178bbce.jpg?t=1356511362
http://mob1056.photobucket.com/albums/t380/uniflow/IMG_0522_zpsce09d679.jpg?t=1356511471

Yes you mentioned when we talked about the trouble you had with the splitter cable TPS (probably of a Suzuki RGV i guess?
I wonder if as well as the cable hang up issues the output signal was to course because it was designed to run the solenoids and maybe a ignition function only.
I amended my pic to one better match TZ's inlet port and on talks with people re the butterfly vs slide throttle body people often say the throttle response is more acceptable i guess due abrupt nature of the shape change i proposed .
So i have amended the shape slightly as well.
<img src=" " width="340px"/>
<img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=271438&d=1349936528" width="340px"/><img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=280125&d=1363679839" width="170px"/>

I think a proper linear potentiometer would offer finer control (eg like suspension telemetry uses or the fader from an old volume control to contrast etc Remember those :)
from memory there is even simple circuits available to condition their output to gain the desired outputs to throttle travel.

<img src="http://www.pennyandgiles.com/script_cms/get_image.php?imageID=317&new_w=420" width="240px"/><img src="http://www.onlinetps.com/shop/images/item_images/slider_tone.JPG" height="160px"/>
But what side up would the cut out go? wonder?

A flatter more wedge shape should be ultra short.
As it needs no area to blend the port weith the intake as well and help to clear the blocking effects of the crank wheels on The gp125.
<img src="http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=267359&d=1343721680" width="240px"/>

Assuming the rotary valve GP125 engine is to be freed from the shackles of a carb.

Your ball throttle is super neat but well beyond us mere mortals;)
I absolutely love the variable rotary valve slider you did.
I see that as a far simpler solution than either the ball valve or my half arsed Photoshop effort i have done, if combined directly with a potentiometer.

<img src="http://i1056.photobucket.com/albums/t380/uniflow/0c93ef14.jpg" width="240px"/><img src="http://i1056.photobucket.com/albums/t380/uniflow/c0231e31.jpg" width="240px"/>

[Forgi]

The problem here is that both examples you have given i would never work with.
Any 70 cc RACING engine at 10,000 rpm isnt even into the powerband, let alone pushing the limits of power with those timings.
All the work I have done is with full noise designs that are pushing the limits of what can be achieved in every area I can modify.
Trying to use my guide of making the header equal to the total Ex effective area, and making the duct nozzle = 75%, in an engine that wont make any power anyway, is
missing the point entirely.

Ok Wobbly, I can understand, you alright! I think basically we are talking about the same thing, but from different point of view.

I want to make clear that my examples of course are not about the max capacity as I'm talking about only 10k rmp. At 12-13K rmp a simple port won't generate a convenient blowdown STA even if we increase the exhaust port's angle up to 200 degrees.
Of course there is a huge and notable connection between the two things, but it would be hard for me to explain it in english.

Anyway, I'm gonna test it and if you are interested I'd share the results. Thank you for the conversation!

[wobbly]

The thing that overrides all of the thoughts on this connection between the duct vol/exit area - and blowdown capability,is that we are talking about cases where
we have huge ( relatively ) blowdown STA.
This implies that the engine is designed for extremely high power capability.
In these cases the Exhaust effective area and thus STA becomes pretty much irrelevant.
To the point that its a proven case we only need around 75% of this effective total exhaust area at the flange to achieve these high power levels.
As I have noted before, we can use the 75% guide, or simply calculate the main port area , and construct the duct to equal this - basically ignoring the big Aux ports completely.
All of these ideas have been tested on very high output race engines, now if you want to extend the thought pattern, to adapt the small duct to low power applications, then thats
completely fine - but I have no idea of the benefits, if any.

[Yow Ling]

I wonder if as well as the cable hang up issues the output signal was to course because it was designed to run the solenoids and maybe a ignition function only.

Not really convinced over the Coarse or Fine outputs from a TPS, if it is a potentiometer and you put a potential of 12v on the top , earth at the bottom, then assuming it is a carbon or ceramic track you will get an infinite range of 0 to 12v off the wiper . if it is wirewound with say 100 turns then you will get 100 steps about 1% still not exactly coarse. if it was a switch then you could say it was coarse, even if it had multiple taps.

[Flettner]

My TPS, although in cable, was a rotating device ( in fact the very same unit I'm using now ). The first cable went round a rotating quadrant, then a second cable off to the slide throttle ( a lake injector copy ). I had times when the slide would " hook up slightly " but the TPS not. Leeeean off idle but only sometimes untill I caught it in the act one day!! So that was the end of that, no more cable between these two units. I not telling anyone to do as I have done, just saying this is what happened to me.