ESE's works engine tuner

[richban]

More intake info that might help. Most of this is over my head but you may get something from it. http://www.profblairandassociates.com/pdfs/Bellmouth.zip

[TZ350]

.


More intake info that might help. Most of this is over my head but you may get something from it. http://www.profblairandassociates.com/pdfs/Bellmouth.zip

Interesting post

I have just down loaded and read it. The new Keihin and OKO copy carbs I have been looking at recently look like Fig 7 with the elliptical intake profile and are apparently the best shape according to Blair. Which is interesting because they are visibly different to the traditional Mikuni bellmouth.

.

[richban]

.



Interesting post

I have just read it. The new Keihin and OKO copy carbs I have been looking at look like Fig 7 with the elliptical intake profile and is apparently the best shape according to Blair. Which is interesting because they are visibly different to the traditional Mikuni bellmouth.

.

The bellmounth on the TM28 I am using looks very crude in compassion with some of the Keihin models. I am going to try adding a radious to the carb bellmounth in affect creating a 10mm trumpet. Then airbox. Also looking at a flat floor in the carb body for more flow. Mr Mikuni recons that a 28mm is fine for around 30hp and will flow nice up to 130000 rpm so should be fine for my bike.

[TZ350]

I have looked at this in the past. I can't remember what bike it was but it had a flap inside the air box that increased and decreased the volume on throttle position (quite nifty). When I fitted a make shift air box to my bike everything started to come together. I am working on 2 exhausts at the mo. When they are built I will be making some air boxes to try with each pipe. I reckon there are big gains to be made.

Its very encouraging to hear from someone who has tried this before and had some success with it.

.

[TZ350]

The bellmounth on the TM28 I am using looks very crude in compassion with some of the Keihin models. I am going to try adding a radious to the carb bellmounth in affect creating a 10mm trumpet. Then airbox. Also looking at a flat floor in the carb body for more flow. Mr Mikuni recons that a 28mm is fine for around 30hp and will flow nice up to 130000 rpm so should be fine for my bike.

It is interesting that a 28 is good for 30hp, our 24mm flow tubes that we use for sleeving down larger carbs, pass as much air as a 28mm carb does. I read some where that people spend a lot of time porting their motors but overlook the carb and that big gains can be made by working on the carb.

.

[TZ350]

Resonant Airboxes: Theory and Applications:- http://motorcycleinfo.calsci.com/Airboxes.html

resonant rpm = 9550 sqrt( 116.5 A / VL ) (single cylinder 2-stroke)

Where the A=area of the inlet tube in cm2, V=volume in cc’s, L=length of the inlet tube in cm’s.

The theory is that the maximum volume of air, will flow through a 24mm carburettor when it is in resonance with a plenum.

After playing with the numbers I found that with a plenum of 1000cc and an inlet tract diameter of 24mm the inlet will be good for a resonant point from 6 to 12,000 rpm.

As I have a new ignition system that can control a servo motor I can use this to move the resonant point from 6 to 12 by either changing the length of the inlet or the volume of the plenum.

Today I was pleased to find this on the net, at http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.html a graph of the resonant frequency of a Coke bottle. And 100 to 200 Hz is equivilent to 6-12,000 rpm for a single cylinder 2-stroke.

The volumes and neck diameter are smaller but in proportion to my planned plenum chamber. Its pretty exciting as it means I am on the money with the sizing of the resonant system for my engine and it will phsically fit on the bike.

.

[richban]

It is interesting that a 28 is good for 30hp, our 24mm flow tubes that we use for sleeving down larger carbs, pass as much air as a 28mm carb does. I read some where that people spend a lot of time porting their motors but overlook the carb and that big gains can be made by working on the carb.

.
Yeh on the mikuni graph 28mm will do 30 just. I am going to try a flat floor on one of the carbs I have to see if top end is effected with adding more volume. Similar to going to a 30mm with out buying a new carb. I think the bike with the fancy airbox was a bluell of all things. After 6 months of trying to get me engine tuned the one thing I did learn is exhaust and carburetion are not to be taken lightly and can have huge effects on performance on a standard type engine or a hot one.

[richban]

Resonant Airboxes: Theory and Applications:- http://motorcycleinfo.calsci.com/Airboxes.html

resonant rpm = 9550 sqrt( 116.5 A / VL ) (single cylinder 2-stroke)

Where the A=area of the inlet tube in cm2, V=volume in cc’s, L=length of the inlet tube in cm’s.

The theory is that the maximum volume of air, will flow through a 24mm carburettor when it is in resonance with a plenum.

After playing with the numbers I found that with a plenum of 1000cc and an inlet tract diameter of 24mm the inlet will be good for a resonant point from 6 to 12,000 rpm.

As I have a new ignition system that can control a servo motor I can use this to move the resonant point from 6 to 12 by either changing the length of the inlet or the volume of the plenum.

Today I was pleased to find this on the net, at http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.html a graph of the resonant frequency of a Coke bottle. And 100 to 200 Hz is equivilent to 6-12,000 rpm for a single cylinder 2-stroke.

The volumes and neck diameter are smaller but in proportion to my planned plenum chamber. Its pretty exciting as it means I am on the money with the sizing of the resonant system for my engine and it will phsically fit on the bike.

.

That should be easy to test on the dyno with a collapsable mockup airbox with marked off volume positions. Then you could test the maths see what works then build your robot airbox. Very cool.

[TZ350]

Yeh on the mikuni graph 28mm will do 30 just. I am going to try a flat floor on one of the carbs I have to see if top end is effected with adding more volume. Similar to going to a 30mm with out buying a new carb.

I would be very interested to see the Mikuni graph if you have a link or PDF you could post. I have not heard about flating the floor of a carb before. I would be interested in knowing more about it.

I will try your idea of the adjustable mockup air box, thanks.

.

[Yow Ling]

So if you had an engine that used a powervalve, you could connect the PV cables to the variable airbox and control 2 thing at the same time without too much extra control complexity, not too many PV buckets around yet !

[TZ350]

So if you had an engine that used a powervalve, you could connect the PV cables to the variable airbox and control 2 thing at the same time without too much extra control complexity, not too many PV buckets around yet !

We have just receved a digital ignition from Ignitech that can control PV's and we have a PV servo from an RGV to use, we also have a few RGV cylinders too. The ignition can also be programed to inject water into the exhaust to widen the power band.

It will be interesting if we can make any of this work properly.

.

[Yow Ling]

Yes those Ignitechs really do look like the dogs knob, for about 100 euro you get alot of features, the launch contol looks pretty amazing, I will be ordering one soon, if anyone is interested you can save about 15 euro by buying more than one unit at a time

[richban]

I would be very interested to see the Mikuni graph if you have a link or PDF you could post.

.

It is on page 11 of the VM tuning manual its a rough guide but was a good place to start for me. Also it points to making around 23hp max with a 24mm. But this is for a round slide VM. I would imagine you would get more out of a good flat slide. If you made a D floor you should still be with in the rules as the spigot would still be 24mm. If it works??

http://www.mikunioz.com/download/pdf_files/vmmanual.pdf

[Bert]

I would be very interested to see the Mikuni graph if you have a link or PDF you could post. I have not heard about flating the floor of a carb before. I would be interested in knowing more about it.

I will try your idea of the adjustable mockup air box, thanks.

.

This is starting to get very interesting again, didn't some of the old TZ125 's run a flat bottom mikuni carbs?? (i'll have to find the page i was reading)...

Resonant and intake lengths seem to be the forgotten bit (and most miss understood part) of tuning, it timely that this has come up been looking into building an usefull airbox for my TF.


anyhow, this might be interesting to some:
http://www.bgideas.demon.co.uk/tmanual/Tm_Ch2.pdf

[richban]

I wish I paid more attention to maths at school.

[TZ350]

Yes those Ignitechs really do look like the dogs knob, for about 100 euro you get alot of features, the launch contol looks pretty amazing, I will be ordering one soon, if anyone is interested you can save about 15 euro by buying more than one unit at a time

We got the SPARKER DC-CDI-P2 race http://www.ignitech.cz/english/aindex.htm because it is for 2-strokes and has all the bells and whistles.

This unit has a water prof plug and there is also an option to purchase it with the plug pre wired with 2m loose leads for a few extra Euros. This is a very worthwhile option, saves a lot of work. We also purchased a spare pr-wired plug. We also purchased the trigger coil, HT coil, trigger rotor for the crank and a heap of crimp lugs.

We have only just started looking at it, but for a single cylinder 2-stroke, I think the unit works by detecting a trigger pulse, and then waiting 360 degrees plus or minus the advance/retard selected before firing the CDI

.

[TZ350]

This is starting to get very interesting again, didn't some of the old TZ125 's run a flat bottom mikuni carbs?? (i'll have to find the page i was reading)...

Resonant and intake lengths seem to be the forgotten bit (and most miss understood part) of tuning, it timely that this has come up been looking into building an usefull airbox for my TF.


anyhow, this might be interesting to some:
http://www.bgideas.demon.co.uk/tmanual/Tm_Ch2.pdf

Thanks for the link

I had a look and here is the complete set..........

Power…………………. http://www.bgideas.demon.co.uk/tmanual/Tm_Ch1.pdf
Breathing & Induction.. http://www.bgideas.demon.co.uk/tmanual/Tm_Ch2.pdf
Combustion…………... http://www.bgideas.demon.co.uk/tmanual/Tm_Ch3.pdf
The Exhaust System…. http://www.bgideas.demon.co.uk/tmanual/Tm_Ch4.pdf
Camshafts…………….. http://www.bgideas.demon.co.uk/tmanual/Tm_Ch5.pdf
Ignition Systems……… http://www.bgideas.demon.co.uk/tmanual/Tm_Ch6.pdf
Turbo or Supercharger.. http://www.bgideas.demon.co.uk/tmanual/Tm_Ch7.pdf
Engine Reliability…….. http://www.bgideas.demon.co.uk/tmanual/Tm_Ch8.pdf

.

[TZ350]

The Suzuki GP’s carburetor housing makes a natural 2000cc resonant plenum chamber. The idea is to have a 33mm intake for the motor drawing from the chamber and a 24mm carb filling the chamber.

With an inlet duration of 220 degrees the motor is only sucking for 2/3rds of the time but the 24mm carb is feeding the chamber all the time and if we get the resonance thing working properly the chamber will be pumped up to a higher pressure than atmospheric, maybe by as much as 10-15%.

So by the time the engine takes another gulp from the chamber, it has been completely re-filled with high pressure air. And from the law of "partial pressures" 125cc from 2000 means that on the suction stroke the pressure in the chamber has been reduced about 6%, not much, particuarly if it was 10-15% higher to start with.

In theory this means the motor will be getting a much better fill of air from the resonant plenum chamber than it could have by sucking directly through a carb, even a carb much bigger than 24mm. From our experiance with the flow bench we think it might be possible to suck as much air through a 33mm flow tube as through a 38mm carb.

Pic-01 24mm cover on the left modified 33mm inlet on the right.
Pic-02 33mm bellmouth for the modified rotary valve cover.
Pic-03 the old 24mm carb.
Pic-04 the new 33mm bellmouth feeding directly to the motor.
Pic-05 the 24mm carb feeding the plenum chamber.

[speedpro]

I can feel a protest coming on , , , there must be some cheating going on somewhere here.

[TZ350]

I can feel a protest coming on , , , there must be some cheating going on somewhere here.

Same 24mm carb.........Cheating....Maybe.....Maybe Not.....:sweatdrop...so what do the legals think?....:oi-grr:...cheat..or....:2thumbsup...ok

[Yow Ling]

Same 24mm carb.........Cheating....Maybe.....Maybe Not.....:sweatdrop...so what do the legals think?....:oi-grr:...cheat..or....:2thumbsup...ok

I would go with legal, tricky but legal. I wonder if there will be a "Cyclone " effect (or a dyson bagless vacume effect) where the fuel may drop out of suspension with the air as it turns to go down the black hole. Of course if it works we will all fit it , and down here where the ESE brand isnt so well known, we will claim it as our own !!

mmm a good backfire into 2 litres of fuelair could be spectacular,

[bucketracer]

I would go with legal, tricky but legal. I wonder if there will be a "Cyclone " effect (or a dyson bagless vacume effect) where the fuel may drop out of suspension with the air as it turns to go down the black hole. Of course if it works we will all fit it , and down here where the ESE brand isnt so well known, we will claim it as our own !!

mmm a good backfire into 2 litres of fuelair could be spectacular,

They have to get it to work first :laugh: and I won't be standing any were near it.

When TeeZee tries to start it up, I will be heading for the hills, no doubt followed by the rest of the workshop :chase: ...................:scooter:

[Sketchy_Racer]

To Quote MNZ rules:

"F4 2 stroke engines over 104cc are restricted to carburation equivalent to a single 24mm
carburettor"

If it is drawing through a 24mm carburetor, then that is all that matters is makes no mention to the "intake port volume" which is essentially what a plenum chamber like that is. I think it is an excellent idea and if would work even better if you had a better shaped plenum chamber than the casting of the GP125 motor.

[SS90]

Same 24mm carb.........Cheating....Maybe.....Maybe Not.....:sweatdrop...so what do the legals think?....:oi-grr:...cheat..or....:2thumbsup...ok

I can't see that as cheating.....anyone else?
I am very interested in the real measurable results though....what about mixture strength at different RPM's?, with previous discussions we have had over intake volumes etc, I foresee some strange carburation situations.

Time will certainly tell however, and I recon it would be a worthwhile experiment (if not perhaps a little frustrating!)

[TZ350]

I foresee some strange carburation situations.

Time will certainly tell however, and I recon it would be a worthwhile experiment (if not perhaps a little frustrating!)



Will it work?.:sherlock:.Who knows, I have some doubts too, but its an adventure, and it could be good, lets see what happens

.

[gav]

OK, some one has to play Devils Advocate ....
If the rule says this
To Quote MNZ rules:

"F4 2 stroke engines over 104cc are restricted to carburation equivalent to a single 24mm
carburettor"

And now modified it draws more air than before, then it is no longer equivallent to the single 24mm carb is it? Just a thought .... ???

[Yow Ling]

OK, some one has to play Devils Advocate ....
If the rule says this
To Quote MNZ rules:

"F4 2 stroke engines over 104cc are restricted to carburation equivalent to a single 24mm
carburettor"

And now modified it draws more air than before, then it is no longer equivallent to the single 24mm carb is it? Just a thought .... ???

Ok mr devil, thats just silly, the thing is still sucking through a 24mm hole, next you will say racing on cold days is illegal for 125 aircooleds because they get more air into the engine when cold.

The rule seems to be based on the area of the intake , not the amount of airflow



OK maybe the world is pushing the air through the 24mm hole but its still a 24mm hole (or its equivelent)

[Bert]

I've been thinking about this for a while now. but still came to the same conclusion. as follows:

To Quote MNZ rules:

"F4 2 stroke engines over 104cc are restricted to carburation equivalent to a single 24mm
carburettor "

My original understanding is that 24mm restriction (when they first introduced 125s) was to level the playing field between 100cc and 125cc 2 stroke engines.

The restriction does not define either: the engineered shape, nor restricts the efficiency of how the equivalent 24mm single carburettor is engineered. (Otherwise the rules would clearly have to state the homologated carburettors; fit for the intended rule purpose).
So with this in mind; as long as there is some form of 24mm restriction within the intake structure (within the carburetted section) then how it is engineered or applied is not really a contentious issue. fuel injection will open up the same can of worms in the future...

my two cents on the topic.

[F5 Dave]

With restrictor plates in some silly car classes the go was to make sure it leaked like buggery & just jet rich thus getting more than an x mm2 area. Of course that is cheating & on a 2 stroke likely to cause it to seize anyway esp on closed throttle.

Mike is just winding you up, totally legal I would think. On a constant speed engine this just might be able to work.

Personally I don't think you have a chance of making a racing engine, but am prepared to be proved wrong. Plenty of people have run rotary disc engines with super long radiator hose with a carb on the end & seemed to go ok.

[SS90]

With restrictor plates in some silly car classes the go was to make sure it leaked like buggery & just jet rich thus getting more than an x mm2 area. Of course that is cheating & on a 2 stroke likely to cause it to seize anyway esp on closed throttle.

Mike is just winding you up, totally legal I would think. On a constant speed engine this just might be able to work.

Personally I don't think you have a chance of making a racing engine, but am prepared to be proved wrong. Plenty of people have run rotary disc engines with super long radiator hose with a carb on the end & seemed to go ok.

I have done the same myself (super long radiator hose for inlet manifold) and everything worked "as it should", with no adverse effects, which is actually what lead to my studies (and experiments) on inlet manifold lengths.

I am not 100% certain that it will work, but I really believe that Teezee should perceiver with the concept, just because books etc don't suggest that it won't work doesn't mean it won't.

The pictures he posted of the cases show just how easy it will be to effect the design he want's (not that much work really) as it is "half done" already

Will it work?

Only Pop's Yoshimura knows, but I suspect we all will if Teezee can get the system working.

Do you have a day Job Teezee?

[F5 Dave]

Popet Yoshimura would know shit about real engines, only Cams & valves & such:lol:

Yes he does have a day job, but his boss knocked himself silly in the TRRS so is easily convinced that TZ sitting at the PC is bonafida 'work'

[TZ350]

.

Havn't been able to make any sense of it all yet, we can easily find the resonant frquency of all sorts of pipes drums etc around the work shop and even of the test speaker but not the GP's chamber???????????

Pic-01 Thomas making up a 0.5W amp from JayCar
Pic-02 Amp, Speaker, and short test pieces.
Pic-03 The GP setup for test.
Pic-04 Alexi doing some real work............
.

[jasonu]

If it wins then clearly it is a cheater...

[koba]

With restrictor plates in some silly car classes the go was to make sure it leaked like buggery & just jet rich thus getting more than an x mm2 area. Of course that is cheating & on a 2 stroke likely to cause it to seize anyway esp on closed throttle.

Mike is just winding you up, totally legal I would think. On a constant speed engine this just might be able to work.

Personally I don't think you have a chance of making a racing engine, but am prepared to be proved wrong. Plenty of people have run rotary disc engines with super long radiator hose with a carb on the end & seemed to go ok.


http://worldrally.motorsportforum.com/forums/showthread.php?t=121013

If any bastard tries that on a bucket...

[Buckets4Me]

If it wins then clearly it is a cheater...

well then I will go fit the rs engine back into my bike and be all legal then :)

(I couldn't ride half as well as the top guys so it cant be cheating to use a race engine now can it)

[Henk]

Excellent excuse. I'll start looking for an RS.

[TZ350]

Other links collections can be found on pages 80, 90, 100, 110

From a link posted by Bert
Power…………………. http://www.bgideas.demon.co.uk/tmanual/Tm_Ch1.pdf
Breathing & Induction.. http://www.bgideas.demon.co.uk/tmanual/Tm_Ch2.pdf
Combustion…………... http://www.bgideas.demon.co.uk/tmanual/Tm_Ch3.pdf
The Exhaust System…. http://www.bgideas.demon.co.uk/tmanual/Tm_Ch4.pdf
Camshafts…………….. http://www.bgideas.demon.co.uk/tmanual/Tm_Ch5.pdf
Ignition Systems……… http://www.bgideas.demon.co.uk/tmanual/Tm_Ch6.pdf
Turbo or Supercharger.. http://www.bgideas.demon.co.uk/tmanual/Tm_Ch7.pdf
Engine Reliability…….. http://www.bgideas.demon.co.uk/tmanual/Tm_Ch8.pdf

Toyota turbo cheat, posted by Koba
http://worldrally.motorsportforum.com/forums/showthread.php?t=121013

All you want to know about physics and resonance
http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.html

IgniTech programmable ignitions for race bikes
For 2-strokes get the SPARKER DC-CDI-P2 race http://www.ignitech.cz/english/aindex.htm because it is has all the bells and whistles

Resonant Airboxes: Theory and Applications:- http://motorcycleinfo.calsci.com/Airboxes.html

24mm carb for 30+ hp go-cart engines
Carb-01 http://www.out2win.com/catalog/images/ibeal5.jpg
Carb-02 http://www.out2win.com/catalog/ibea.html
Carb-03 http://www.j3competition.com/downloads/technical/L6_Homologation.pdf

Expansion Chamber Design According to Blair:-
http://members.bellatlantic.net/~vze2p5sj/modelengines/expcham.htm

We see that the flow bends upwards and forward towards the exhaust port as the cycle proceeds and the piston rises to shut the port.
Abstract taken from http://www.lortim.demon.co.uk/vsih/pistons.htm

Port/Time/Area Jennings page 81-82 http://www.vintagesleds.com/library/manuals/misc/Two-stroke%20Tuner%27s%20Handbook.pdf

Two Stroke Tuners Hand-Book http://www.datafan.com/TunersHandbook/2-strokefiltered.html

The specs of Avalons Team ESE's BOB Suzuki GP125 20 rwhp engine:

Skim the barrel 1.5mm and “o” ring it, no head gasket, thin alloy spacer plate under the barrel and Suzuki RG250 pipe modified to RM125 specs, KX80 ignition. Raise the exhaust to open 83 deg ATDC, and widen to 70% of the bore, cut 30 deg from the closing point of the rotary disk, so inlet opens 145 BTDC and closes 85 ATDC. Champher the inlet side of the crank at 45 deg to aid inlet flow. Set the mj about 102.5 105 107.5 and ignition timing, 26-28 BTDC using a dyno. A link to Bells book and the RM pipe specs can be found on page 100 of this thread.

Cheep easy effective mods that most anybody can do and get 20 rwhp from a Suzuki GP125.

.

[TZ350]

.

Ilmor Engineering, http://www.ilmor.co.uk/ the British company that came to MotoGP briefly in 2006 and 2007, has now developed a turbocharged, 700cc, three-cylinder, five-stroke petrol engine which might someday be used on a motorcycle.

So Team ESE :blink: are not the only ones at the cutting edge of racing motor cycle technolagy.......

.

[SS90]

Other links collections can be found on pages 80, 90, 100, 110



We see that the flow bends upwards and forward towards the exhaust port as the cycle proceeds and the piston rises to shut the port.
Abstract taken from http://www.lortim.demon.co.uk/vsih/pistons.htm


.

I'm just having a look at this link Teezee, and it has some accurate information regarding scavnge patterns, but I just thought that people would be interested in this paragraph.

When a jet of gas penetrates an almost stationary medium, its velocity changes in accordance with Newton's law of momentum. The wave front takes on a mushroom like appearance, and when the overhanging edge curls round and enters the exhaust port then short circuit waste of new gas starts. The short circuit generally starts in earnest about 25o after port open, and continues for the remainder of the port open period. The minimum effective distance between the exhaust port and the transfer port has been determined at 6% of stroke (about 4.5_mm on our 72_mm stroke engines). This is some 50% larger than the rule of thumb passed down from an earlier era. Changing the primary compression ratio, or the main compression ratio, has no measurable effect of the swirl-scavenge action.

The last sentence is incorrect (in my experience), and it's quite important!

Lower primary compression reduces short circuiting dramatically, particularly when running large port area's.

Pretty much everything else they write is on par with my observations of my tests.

[koba]

Hopefully no dickhead will be in my grid position this year and I manage to finish the race this time, its not fun sitting on the infield watching.

19th December 2009

[TZ350]

I'm just having a look at this link Teezee, and it has some accurate information regarding scavnge patterns, but I just thought that people would be interested in this paragraph.
Changing the primary compression ratio, or the main compression ratio, has no measurable effect of the swirl-scavenge action.

Lower primary compression reduces short circuiting dramatically, particularly when running large port area's.

Pretty much everything else they write is on par with my observations of my tests.

...… it seems counter intuitive that changes in the primary compression ratio wouldn't effect the scavenge pattern.

The booklet is in part a re right of Blair’s work, and an account of how they have applied it to their racing engines.

I know, it's Villers Engines :zzzz: But it’s a good effort and I think very informative, it’s worth a careful read. Actually it makes Villers engines and vintage racing look interesting.

Here is a bit about the transfers much like the unmasking you encouraged me to look at earlier.

“The vast majority of the gas to be pumped up the transfer ports comes not from the crankcase but from under the piston as it descends, and the gas has to do a 180 turn to go up the transfers …………………… From this it can be seen that any tuning effort would be wisely directed to the underside of the piston, smoothing out any sharp edges on the gudgeon pin boss and particularly the transfer cutaway, which should accurately match the cylinder cutaways at BDC.”

http://www.lortim.demon.co.uk/vsih/pistons.htm

I couldn’t find a date but it looks to be written in the mid 90’s, what do you think?

[TZ350]

I had a bit more of a look at the web site and found the Villiers Singles Improvements Handbook can be purchased here using Paypal:- http://www.lortim.demon.co.uk/pdfbook.htm

From the induction section of the Villiers Singles Improvements Handbook:-
http://www.lortim.demon.co.uk/vsih/carburat.htm

“To achieve the nominal choke size the following formula should be used.
Nominal choke size (mm) = 0.8 x (swept volume x rpm/1000)^(1/2)
207 cc racing motor at 8500 rpm: 0.8 x (207 x 8.5)^(1/2) = 33.5 mm”

So for my Suzuki GP125 at 11,500 rpm the carburettor choke size required is
=0.8 x sqrt (125 x 11.5)
=0.8 x sqrt (1437.5)
=0.8 x 37.9
=30mm

For 9,000 rpm its 27mm and 10,500 its 29mm and 12,500 its 32mm

So according to the Villers handbook, even at 9,000 rpm the F4 rule of a max 24mm carb for a 125 2-stroke is way to restrictive for good power.

Luckily, like Black Adder I have a cunning plan, a plan so cunning that you could put a tail on it and call it a weasel.

.

[gav]

So according to the Villers handbook, even at 9,000 rpm the F4 rule of a max 24mm carb for a 125 2-stroke is way to restrictive for good power.

Luckily, like Black Adder I have a cunning plan, a plan so cunning that you could put a tail on it and call it a weasel.

.
Umm, so its taken you 120 pages to reach that conclusion then? Hehehe, thats why most go with a 100cc bucket.
Nah good to see your progress, has been very informative, thanks for your efforts!

[bucketracer]

You might not be that far off. I have had a play with the choke size numbers.

8K=25mm choke 12K=32mm choke

8K is 2/3 of 12K so if your using a plenum, and 8K passed air all the time wouldn’t it be able to keep up with the demands of 12K sucking from the plenum for only 2/3 rds of the time?

In other words through the use of a plenum a 24mm carb that’s open all the time could feed a 32mm choke that is only opened by the inlet rotary valve for 2/3 rds of the time and keep it supplied with all the air it can swallow.

I think you might be onto it.

[Buckets4Me]

You might not be that far off. I have had a play with the choke size numbers.

8K=25mm choke 12K=32mm choke

8K is 2/3 of 12K so if your using a plenum, and 8K passed air all the time wouldn’t it be able to keep up with the demands of 12K sucking from the plenum for only 2/3 rds of the time?

In other words through the use of a plenum a 24mm carb that’s open all the time could feed a 32mm choke that is only opened by the inlet rotary valve for 2/3 rds of the time and keep it supplied with all the air it can swallow.

I think you might be onto it.

Ok I get it

32mm choke = 12,000 x 125cc x 2/3 = .........…. 1,000l/m out of the plenum through the 32mm flow tube and into the motor.

25mm choke = 8,000 x 125cc = 1,000l/m x 3/3 = 1,000l/m flow through the smaller carb and into the plenum chamber.

Its all in balance because the 25 is flowing for1/3 longer than the 32

[=cJ=]

Only problem I see is persuading the engine to suck continuously, rather than just when the inlet port's open, though I am guessing this is where the tuning of the plenum comes in?

[Buckets4Me]

or the opening facing forwd :)
then engine would not have to suck so much as swollow or GULP at taupo

[bucketracer]

then engine would not have to suck so much as swollow

I have allways had a preference myself for engines that suck then swollow :)

[SS90]

...… it seems counter intuitive that changes in the primary compression ratio wouldn't effect the scavenge pattern.

The booklet is in part a re right of Blair’s work, and an account of how they have applied it to their racing engines.

I know, it's Villers Engines :zzzz: But it’s a good effort and I think very informative, it’s worth a careful read. Actually it makes Villers engines and vintage racing look interesting.

Here is a bit about the transfers much like the unmasking you encouraged me to look at earlier.

“The vast majority of the gas to be pumped up the transfer ports comes not from the crankcase but from under the piston as it descends, and the gas has to do a 180 turn to go up the transfers …………………… From this it can be seen that any tuning effort would be wisely directed to the underside of the piston, smoothing out any sharp edges on the gudgeon pin boss and particularly the transfer cutaway, which should accurately match the cylinder cutaways at BDC.”

http://www.lortim.demon.co.uk/vsih/pistons.htm

I couldn’t find a date but it looks to be written in the mid 90’s, what do you think?

I will download the whole book I think.

From what I have read so far, it seems pretty good, just because it's about Villiers doesn't mean it isn't any good!

The new piston designs that come out still concentrate on just the unmasking ideas we have discussed (some are really expensive), and rather than simply rely on the boost port supplying more fuel via the reeds (in the case of reed induction, which is where the majority of work is happening nowadays), they put alot of effort into ensuring as complete scavenging of under the piston as possible with-out sacrificing reliability .

It seems too that with the higher crankcase volumes benefit more from work in this area (logically).

To dredge up another concept that has been discussed, I just have to agree with sonicV that a new pipe is in order (if anything I would change the baffle cone angles and
lengths , putting up with a "hole" in the midrange to enable you to get a longer peak power curve in the upper RPM.

I have still never seen a 125cc engine with a 24mm carb that puts out more than 22 PS, did you manage to find some power curves for these Kart engines that claim 30PS?

I'm really interested in how this experiment progresses, because if it works I would certainly use your data to start my own experiments.

It's winter now, and I am starting to have some spare time on my hands again!

[F5 Dave]

...… “The vast majority of the gas to be pumped up the transfer ports comes not from the crankcase but from under the piston as it descends, and the gas has to do a 180 turn to go up the transfers ………

So logically it would make sense to reduce the crankcase volume to approach zero & fit as tall piston as possible, :shifty:

which is largely what those engines did.

[Yow Ling]

Could we consider the crankcase volume to be like a spring then the more cranckcase volume the softer the spring, you still end up pumping the same (give or take) volume , just the delivery characteristic changes. This seems to make the whole port time thing make some more sense.

[SS90]

It comes back to the "pumping loss" concept again (as well as delivery ratios). I'm unsure what mixture strength problems TeeZee's concept will encounter, but like F5dave I have seen plenty of 2 strokes with massively long radiator hoses for inlet manifolds/plenums, and they worked fine....... I personally don't know of anyone who went to the effort of measuring the resonant frequency though, so that has to be advantage for heading in the right direction, and getting maximum and minimum values for intake volumes etc.
And (hopefully) the engine will make more power!

[TZ350]

“Save the stuffing around and go buy one of these digital, programmable ignitions http://www.ignitech.cz/english/aindex.htm originally posted by K14 ”

We have taken K14’s advice and purchased a digital/programable DC-CDIP 2 Race 2-Stroke IgniTech ignition.

“This is about the latest RACE Ignitech and our ignition systems: http://www.twostrokeshop.com/ignitech_race.htm

Here is an article showing how to modify the RZ hardware to allow use of the Ignitech twin cdi module, eliminating the wasted spark system and giving full control over all electronic functions. http://www.twostrokeshop.com/ignitech.htm “.

The setup info was found on the Two-Stroke Shop www.twostrokeshop.com site.

There are also units for 4-Stroke, they can be purchased from The Two-Stroke Shop or directly from IgniTech. http://www.ignitech.cz/english/aindex.htm

.

[Bert]

Looks like a good option.
Did you buy them through Wayne or did you get them directly from ignitech??
What was the final ball park cost to get them here?

Also what do they come with, CDI & software, Hall effect sensor as well?

[TZ350]

Looks like a good option.
Did you buy them through Wayne or did you get them directly from ignitech??
What was the final ball park cost to get them here?

Also what do they come with, CDI & software, Hall effect sensor as well?

We got the DC-CDIP 2 Race ignitions directly from IgniTech before Xmas, we didn't know Wayne www.twostrokeshop.com sold them until just now. We got every thing, cdi unit, software, pre-wired plugs coil, trigger, roter and connectors, about $470 NZ a unit.

Unless you speak Chec, IgniTech can't realy help you with setup advice, Wayne is more expensive but he offers invaluable after sales service, its worth considering buying from him just for the after sales support.

.

[speedpro]

I added a tube to my AC50 intake and put the carb on the end. I played with length and diameter. It was interesting how it resonated at various revs and throttle settings. One setup resonated just off idle and the motor really grunted. all the setups i tried were good at one rev or another but all had big holes where they didn't work. i suppose you could tune it to work right at the revs you want, but at the time I couldn't see the advantages outweighing the disadvantages.

When it was resonating it was very loud, way louder than the pipe. Being as advanced and ahead of the times as I was the pipe was an up and over type, exiting under the seat with a titanium muffler. high pipes are so decade before last.

[F5 Dave]

But you have to run a battery with all that Malarky yeah? Do they have a charging cct? I have a Zeeltronics on my RZ500 & it is touchy if the battery voltage sags as often seems to with tiny batteries & it won't start as not enough juice to fire up the electronics.

[TZ350]

But you have to run a battery with all that Malarky yeah? Do they have a charging cct? I have a Zeeltronics on my RZ500 & it is touchy if the battery voltage sags as often seems to with tiny batteries & it won't start as not enough juice to fire up the electronics.

Yes, have to run a battery, I don't like that aspect, I can see some tears before bedtime with the total loss system. I will get it going as is first then look at a charging system. Need to get it going first so I can check the current draw.

You might remember selling me a KX80 ignition with a trigger coil on the outside of the stator plate. I figure I can fit some re-wound coils in place of the internal High Voltage one and keep a small battery charged with them.

.

[F5 Dave]

Yeah it can be a real pain, I've always tried to avoid a battery on a racebike as I'm likely to either;
A) forget to flick a switch & Discharge battery/overheat engine in use if a pump
B) find the battery has gone down in between races (crazy that bigger batteries can last months & still start a bike on the button which takes huge power, yet a brand new small battery disconnected, doing nothing loses volts in a week), or
C) forget to turn up with the battery having put it on charge the night before.

[speedpro]

Yes, but needing a 14.4V battery is a really good excuse to buy a cordless drill with two Lithium Ion batteries and a fast charger. Those Lithium batteries will supply the peak current needed when the coil is charging and have decent energy density as well. Plus the price is right and you get a drill with them.

[Buckets4Me]

Yes, but needing a 14.4V battery is a really good excuse to buy a cordless drill with two Lithium Ion batteries and a fast charger. Those Lithium batteries will supply the peak current needed when the coil is charging and have decent energy density as well. Plus the price is right and you get a drill with them.

is the drill for knee caping the other riders
or core sampling the tank ??

[TZ350]

or core sampling the tank ??

core sampling the tank........very funny :clap:

[TZ350]

Yeah it can be a real pain, I've always tried to avoid a battery on a racebike.

Thats the thing I liked about the JayCar kitset programable ignition, it got its HV from the original KX80 charging coils and a little voltage could be blead off to run the PIC controller, you could set it up to run without a battery.

The IgniTech is different it converts the batterys 12V DC with an inverter to the high voltage required for the CDI and runs the controller from the same 12V battery.

At idle the IgniTech consumes 85mA, at 12V DC. I now have spark in more or less the right place, but have not run the bike yet to see what the current draw is with the CDI being continusly recharged, but I expect I could make a small generator/rectifier unit that would be able to supply the ignition system Ok.

.

[Yow Ling]

Thats the thing I liked about the JayCar kitset programable ignition, it got its HV from the original KX80 charging coils and a little voltage could be blead off to run the PIC controller, you could set it up to run without a battery.

The IgniTech is different it converts the batterys 12V DC with an inverter to the high voltage required for the CDI and runs the controller from the same 12V battery.

At idle the IgniTech consumes 85mA, 12V DC. I have spark in more or less the right place, but not yet run the bike to see what the current draw is with the CDI being continusly recharged, but I expect I could make a small generator/rectifier unit that would be able to supply the ignition system Ok.

.

could always power it with a little Ram Air Turbine (RAT) the Skyhawks used to have them for emergengy power, you would have to run on battery till the race started then switch over to the RAT. Somehow you could incorporate it into the copper finning and carb plenum system to make this idea really fly !

[TZ350]

could always power it with a little Ram Air Turbine (RAT) the Skyhawks used to have them for emergengy power, you would have to run on battery till the race started then switch over to the RAT. Somehow you could incorporate it into the copper finning and carb plenum system to make this idea really fly !

Ok so what happens when I slow down for corners.............

will I have to blow into the RAT untill I get up to speed again?

and would that be known as, having to kiss the Rats arse.........:laugh:

.

[ajturbo]

We got the DC-CDIP 2 Race ignitions directly from IgniTech . We got every thing, cdi unit, software, pre-wired plugs coil, trigger, roter and connectors, about $470 NZ a unit.


.

HOLY UNIT COST batman.......!!!
that is $ 320 MORE than my WHOLE bike cost !!!!!
the mighty GT125 twin.....
but i need more speed and less weight (talking about both the bike and me....)

[Buckets4Me]

HOLY UNIT COST batman.......!!!
that is $ 320 MORE than my WHOLE bike cost !!!!!
the mighty GT125 twin.....


and that would be why even I was able to leave you behind this year at Taupo :)

[ajturbo]

and that would be why even I was able to leave you behind this year at Taupo :)

na... more the fact that the only time i had ridden it was at those races... kept on missing gears..... oh and i suck at racing, MAY have something to do with it...lol

[Buckets4Me]

na... more the fact that the only time i had ridden it was at those races... kept on missing gears..... oh and i suck at racing, MAY have something to do with it...lol

sounds like you ride like I do then :P
last time you where there (I'm sure it was you or somone els on a gt125 with 4 exausts???)
I could only catch you when it was playing up

[Buckets4Me]

https://secure.sportzfotoz.co.nz/popimage.php?imageid=45555 hope this works
Avalon at the bob

https://secure.sportzfotoz.co.nz/popimage.php?imageid=45572
https://secure.sportzfotoz.co.nz/popimage.php?imageid=45535
https://secure.sportzfotoz.co.nz/popimage.php?imageid=45506
https://secure.sportzfotoz.co.nz/popimage.php?imageid=45565
https://secure.sportzfotoz.co.nz/popimage.php?imageid=45570
https://secure.sportzfotoz.co.nz/popimage.php?imageid=45555
and her arch rival on the day
https://secure.sportzfotoz.co.nz/popimage.php?imageid=45505
https://secure.sportzfotoz.co.nz/popimage.php?imageid=45522
https://secure.sportzfotoz.co.nz/popimage.php?imageid=45544


have a look here
https://secure.sportzfotoz.co.nz/image_viewpage.php?eid=168&grp=83

[TZ350]

.

This is my favourite

Avalon at the BOB,

https://secure.sportzfotoz.co.nz/popimage.php?imageid=45555

we have now found 12% extra hp and expect there is more to come,

better start squeezing some extra go out of that CBR............is that possible without it going pop? :bleh:

The next BOB should be interesting.

.

[Ned Kelly]

.

This is my favourite

Avalon at the BOB,

https://secure.sportzfotoz.co.nz/popimage.php?imageid=45555

we have now found 12% extra hp and expect there is more to come,

better start squeezing some extra go out of that CBR............is that possible without it going pop? :bleh:

The next BOB should be interesting.

.

Well TZ the RS Avalon was riding is now in peices at the workshop. It has been pushed pretty hard lately with BOB and the TRRS at Taupo. Time for an overhaul ready for another run at Taupo in March. Hopefully with some new improvements and more Hp.

[gav]

.

This is my favourite

Avalon at the BOB,

https://secure.sportzfotoz.co.nz/popimage.php?imageid=45555

we have now found 12% extra hp and expect there is more to come,

better start squeezing some extra go out of that CBR............is that possible without it going pop? :bleh:

The next BOB should be interesting.

.

Damn, look how small she looks!

[boostin]

Team ESE

During a little clear out around the home I have found a Haynes GP100/GP125 workshop manual. If you want to use it until I ever may need it back you are welcome to it. Otherwise I will put it in the library for future reference.

[Buckets4Me]

Team ESE

During a little clear out around the home I have found a Haynes GP100/GP125 workshop manual. If you want to use it until I ever may need it back you are welcome to it. Otherwise I will put it in the library for future reference.

it could sit next to the 2 I have
or at the workshop with the ones they have there as well :crazy:

Thanks for the offer but we have enough of them to keep us going for some time
also we have the rs125 1994 manual as well :2thumbsup

but if you have any gp125 or 100 engines that would be good
or rs125 forks shokes wheels etc (or the compleat bike any year) let us know

thanks again (I think TZ350 knows the engine inside out by now) he did 5 engine rebuilds in one year

Rick52 may be interested

[F5 Dave]

. . .but if you have any gp125 or 100 engines that would be good
or rs125 forks shokes wheels etc (or the compleat bike any year) let us know

aww gee here's one for ya. Real bargain too.
RS125 (http://www.trademe.co.nz/Trade-Me-Motors/Motorbikes/Motorbikes/Sports/auction-264810862.htm)

No no, its ok, your constant adoration is thanks enough

[Buckets4Me]

aww gee here's one for ya. Real bargain too.
RS125 (http://www.trademe.co.nz/Trade-Me-Motors/Motorbikes/Motorbikes/Sports/auction-264810862.htm)

No no, its ok, your constant adoration is thanks enough

Funny guy :) just about any year BUT no older than 1990 ( I dont want to race pre89 on it)
lol

if it was a 95+ and a few grand cheaper I could be interested :)

[TZ350]

aww gee here's one for ya. Real bargain too.
RS125 (http://www.trademe.co.nz/Trade-Me-Motors/Motorbikes/Motorbikes/Sports/auction-264810862.htm)

No no, its ok, your constant adoration is thanks enough

1980 Honda RS125 don't think so, It looks like an MT125R to me............

[F5 Dave]

Yeah & for 6k, sure buddy, 6 hundy maybe. My RS is an 89 so pre 90.

[Buckets4Me]

but it says rs125 down the side ????
whats going on ?
should I not have put the deposit down

[Kickaha]

.

This is my favourite

Avalon at the BOB,
.

Ian Dawson has what must be the best ever photo of her in a facebook album
http://www.facebook.com/#/photo.php?pid=674833&id=1622289254

[Henk]

Ouch

10 chars

[Pumba]

aww gee here's one for ya. Real bargain too.
RS125 (http://www.trademe.co.nz/Trade-Me-Motors/Motorbikes/Motorbikes/Sports/auction-264810862.htm)

No no, its ok, your constant adoration is thanks enough

Hahah, saw that a week or so ago nearly covered the computer in coffe as soon as I saw the price. Funnyist thing I have seen in months


Ian Dawson has what must be the best ever photo of her in a facebook album
http://www.facebook.com/#/photo.php?pid=674833&id=1622289254

That photo is awsome. Man for all the opurtunities I give people to get pics of me crashing I have nothing that impressive to show

[Buckets4Me]

Ian Dawson has what must be the best ever photo of her in a facebook album
http://www.facebook.com/#/photo.php?pid=674833&id=1622289254

she was doing a during race wof inspection (or scrubing in the new fiberglass and paint)
wanted to see how bright the headlight was

I think it should fly threw a wof(straight over and out the other side)


this one looks much safer
http://www.facebook.com/photo.php?pid=674833&id=1622289254#/photo.php?pid=674836&id=1622289254&fbid=1256576587504

[Buckets4Me]

I see Avalon isn't the only one trying that move
http://www.fatbaq.com/mainpage.phtml?topic=captions&img_id=7

[F5 Dave]

Facebook!?!! Bunch of Gurls!

Post it in a Man's format. Bloody floral print pansies.

[Buckets4Me]

Facebook!?!! Bunch of Gurls!

Post it in a Man's format. Bloody floral print pansies.

what forgotten your login again

[bucketracer]

How do you start a Poll?

Does anyone else think that we should run a sweep stake on the outcome of TeeZee's plenum chamber idea.

I hear he is pretty close, maybe only days away from being able to try it out.

[craisin]

good idea bucketracer

[TZ350]

.

Thomas and Alexi putting the finishing touches to the plenum and fitting a blow off plate.

Next week, hope to get the motor into the bike for a run up the drive, then off to the dyno.

.

[Buckets4Me]

Love the blow off valve (but dose it go wosh)
bet all the boy racers will want one now

[Buckets4Me]

Love the blow off valve (but dose it go wosh)
bet all the boy racers will want one now

[bucketracer]

Plenums and Induction Systems:- http://hemrickperformance.com/induction.aspx

[bucketracer]

An excerpt from:- http://autospeed.com/cms/title_Breathing-Deeply/A_107771/article.html

"The gains available form a well-tuned intake system should not be underestimated. Pioneering work done by Jaguar on their mechanically injected racing engines showed that it was possible to gain more than 100 per cent volumetric efficiencies (VE) by using very long intake runners. This means that the cylinders actually breathed in more than their swept volume! Many manufacturers have since developed efficient tuned intake systems that give very high volumetric efficiencies. As an example, Ford in Australia developed a superb dual-length intake manifold for their straight six, a system that achieves a VE of 100 per cent at the peak torque rpm of 3000.

Power and torque gains of up to 20 per cent have been seen in some engines - and that's as much as is achieved by low-boost turbocharging!

A starting point for working out the length and diameter of intake runners can be gained from the following equations. In a Helmholtz Resonance system (one with runners connected to a common plenum), US-based engineering guru David Vizard suggests that a runner length of 17.8cm at 10,000 rpm makes a good starting point. (In this context, "runner length" refers to the distance from the inlet valve to the plenum chamber.) Add to this length 4.3cm for each 1000 rpm less that the system is being tuned for. Tuning for peak torque (not peak power) is the norm, and so if the engine were being tuned for 4000 rpm, a runner length of 43.6cm would be required. You can see that for an averagely-sized engine bay, the longer the runner that can be fitted in, the better!
Click for larger image

One equation for runner diameter is to multiply the engine volume in litres by the engine's volumetric efficiency, then by the tuned rpm, then divide this sum by 3330. The final figure is square rooted, giving the runner diameter in inches. As an example, a 5 litre engine with an 80 per cent efficiency (expressed as 0.8) and tuned for 3000 rpm, will have a runner diameter of 1.9 inches, or 48 mm.

The volume of the plenum should be around 80 per cent of the volume of the cylinders to which it is connected."

I guess you half the length for a 2-Stroke but use the same runner diameter and it looks like TeeZee's 1.5l plenum could be to big.

[SS90]

Found anything specific to a Two stroke there Bucketracer?

[bucketracer]

Found anything specific to a Two stroke there Bucketracer?

No, would be interesting though. General idea looks Ok, I am looking forward to seeing how TeeZee's plenum idea works out. Just getting it to run will be something.

BTW SS, good bit of detective work spotting Woodys catalytic converter.

[SS90]

The only thing I have found relates to forced induction two strokes and plenums, and none of it very conclusive (other than needing a reed valve).

It will work, by all accounts, but after a bit of development with volumes, lengths etc.

Mounting the carb there has big advantages anyway!

[Buckets4Me]

Mounting the carb there has big advantages anyway!

like it's harder to wipe off ????

[TZ350]

like it's harder to wipe off ????

It will also be easier to change the jets too.............not sure about it facing into the wind though?

.

[richban]

It will also be easier to change the jets too.............not sure about it facing into the wind though?

.

After you get it running you could try a U bend into a volume to keep everything out of the turbulence. I am sure it would have some tuning affect, good or bad don't know.

My own air box design is starting to look quite crude. Might have to read this end of the tread again.192510192511

[bucketracer]

More on Plenums from:- http://urbanracer.com/articles/anmviewer.asp?a=3344&z=38

"The transition between the plenum and runner is the most critical aspect of an intake manifold. It needs to be smooth and harmonious. High-quality manifolds go so far as to have air horns incorporated inside the plenum chamber."

Interesting that TeeZee's plenum has features similar to these high performance plenums, like the internal bellmouth and a single throttle body with open runners to the cylinder.

[richban]

More on Plenums from:- http://urbanracer.com/articles/anmviewer.asp?a=3344&z=38

"The transition between the plenum and runner is the most critical aspect of an intake manifold. It needs to be smooth and harmonious. High-quality manifolds go so far as to have air horns incorporated inside the plenum chamber."

The latest mods to my intake system is just that. Its is matched from the valve to the bell mouth of the carb. Overall length 170mm all I need to do now is create a 12mm long trumpet then putting that into a 1 litre airbox and that should give perfect length to match the exhaust. And 12000 rpm ish

[TZ350]

.

Setting up the IgniTech ignition. This is a great unit, you can leave the LapTop connected while working on the bike and make adjustments on the fly.

.

[speedpro]

You ought to pop the rivets and detach the flywheel. I love the revvy feel of a light crank and found a real advantage when hammering into a corner with being able to snap down the gears without the back wheel skidding. We took the flywheel off my brothers CB125T as well ages ago and I think it made a good difference.

[TZ350]

I love the revvy feel of a light crank and found a real advantage when hammering into a corner with being able to snap down the gears without the back wheel skidding.

Yes, I like the feel of a responsive motor too, but the GP's cranks are quite light compared to a TF or TM crank and we thought we would need some fly wheel effect to retain the phat lazy feel and drivability of the new motor that peaks at only 9,000 rpm for 21.5 rwhp. I will try your suggestion on a modified version of last years motor that peaks at 11,250 for 20 rwhp.

.

[SS90]

Hey Teezee,

I was cc'ing a cylinder head today, and was thinking about the "basic" tunes you use on the GP's

Can you tell me what the compressson ratio's (corrected, and uncorrected) that you use on these engines (with 2mm removed from the top, and a standard cylinder head)

[k14]

You ought to pop the rivets and detach the flywheel. I love the revvy feel of a light crank and found a real advantage when hammering into a corner with being able to snap down the gears without the back wheel skidding. We took the flywheel off my brothers CB125T as well ages ago and I think it made a good difference.
How did you do that? I would like to modify the flywheel on my one but am unsure the best way to go about it. I could make another trigger altogether and that may work but it is a lot of work if it doesn't?

[TZ350]

.

I have got the old GP motor out and started fitting the new motor with its plenum, should be good for a test run Friday then maybe off to the dyno next week.

I was looking at Chambers Yamaha SDR200 today and saw that it has a very large cast alloy air box with a snorkel. I think this must be setup as a resonant chamber for pulse charging the engine. In the pictures the grey piece with SDR on it is the cast alloy air box, it also forms part of the frame.

.

[Brian d marge]

I have an article on the design of belmouths using CFD can try and post it if needed

I do love those Yamaha SDR frames ( cheap as here) , I think ( not sure that they are a bit flexy ,might be ok with the power of a bucket )

Just suspension then ,,,is there any internals that can be modded ?

Stephen

[TZ350]

Hey Teezee,

I was cc'ing a cylinder head today, and was thinking about the "basic" tunes you use on the GP's

Can you tell me what the compressson ratio's (corrected, and uncorrected) that you use on these engines (with 2mm removed from the top, and a standard cylinder head)

Hi SS, give me a few days, as I don't recall and will have to see if there is much in the note books about the measured compression ratios of the "basic" tuned engines.

Not much is left Std., around here any more. In tuned engines I prefer to use 7:1 or there about’s, on the other hand Chambers went to a lot of trouble getting things bang on 8:1 for his 100.

From memory my 7:1's usually finished up about 12 to 13:1 uncorrected, but its a balancing act centred around the exhaust opening point.

In my engines I am always inclined to give a bit away for the sake of reliability, but Chambers loves to take it all to the edge.

.

[TZ350]

I have an article on the design of belmouths using CFD can try and post it if needed

I do love those Yamaha SDR frames ( cheap as here) , I think ( not sure that they are a bit flexy ,might be ok with the power of a bucket )

Just suspension then ,,,is there any internals that can be modded ?

Stephen

Hi Stephen I would be interested in the bell mouth design article. The SDR's frame looks the business, did they handle Ok with the 200 motor? This one is from Japan I think and looks like it has been raced, lots of lock wire, or is that a Japanese boy racer bling thing?. The suspension is long and soft. Can you tell us any more about the SDR's in Japan.

.

[SS90]

Thanks, that would be great.

I was testing some different head designs yesterday (and today), and accidently fitted a head that (I would have thought) was totally unsuitable, as the uncorrected compression ratio measured at 10.6:1 (and 2.3mm head clearance)

Rather than taking it off, just for interest, I ran it up on the dyno, and the power is neigh on identical to a cylinder head with 13.4:1 (after playing with the ignition)

I'm not sure what this means just yet.

[Brian d marge]

yes they are raced http://page5.auctions.yahoo.co.jp/jp/auction/e96755106

I havent tested those frame but I have heard they flex , but thats with a 20 30 hp motor and spindly soft forks

I did see one of those frames on line quite cheap awhile back

I would love to draw one of those frames and load it up on the computer and see what it does !


Stephen

[TZ350]

.

Thanks for the pic.

Could this be what Chambers next Bucket will look like?

.

[F5 Dave]

. . .I do love those Yamaha SDR frames ( cheap as here) , I think ( not sure that they are a bit flexy ,might be ok with the power of a bucket )
. . .
Yeah they look cool & are sort of bucket sized & open enough to take a range of engines. I was eying one up as a mate had one bare with sw. Quick loft, urgh use 2nd hand. Golly! Heavier than they look.

[SS90]

Yeah they look cool & are sort of bucket sized & open enough to take a range of engines. I was eying one up as a mate had one bare with sw. Quick loft, urgh use 2nd hand. Golly! Heavier than they look.

About 13 years ago, I guy I worked with thought the same thing. He used to race 125's as well, and threw a set of old slicks on it, and went out on a few laps, the damned thing tied it'self in knots the first corner, man they are flexy frames!

Put some road tyres back on, and all was well.

[jasonu]

Yeah they look cool & are sort of bucket sized & open enough to take a range of engines. I was eying one up as a mate had one bare with sw. Quick loft, urgh use 2nd hand. Golly! Heavier than they look.

In other words Dave, they are shit piles

[TZ350]

.

Ok the GP-Plenum Chamber is ready for a test ride.

Pic-01 it's ready
Pic-02 look who else has come to see how it goes...Friends of Thomas's...they bet against me in the sweep stake........bastards.
Pic-03 a quick push and it started right up.........starts real easy.
Pic-04 a short punt up the drive, drives well but falls flat over half throttle, hope its just jetting.
Pic-05 it even idles.........hows that. :banana:

If I can sort out the flat spot, its of to the dyno next week.

.

[F5 Dave]

May I suggest at the very minimum some sort of generous front mudguard?

A heavy layer of grease on the castings will hopefully attract any grit/stones that make their way in, or at least tell you how much it is attracting..

[F5 Dave]

In other words Dave, they are shit piles
Yeah. . . but kinda cool looking shit piles in a minimalist lattice frame retro sort of way.

[Ned Kelly]

.

Ok the GP-Plenum Chamber is ready for a test ride.

Pic-01 it's ready
Pic-02 look who else has come to see how it goes......they bet against me in the sweep stake........bastards.
Pic-03 a quick push and it started right up.........starts real easy.
Pic-04 a short punt up the drive, drives well but falls flat over half throttle, hope its just jetting.
Pic-05 it even idles.........hows that.

If I can sort out the flat spot, its of to the dyno next week.

.

Nice work Rob. I must admit I was a bit sceptical. Did you have the helmet on when you fired it up.?

Will see what the dyno says, hope its the start of good Hp.

[TZ350]

.


Nice work Rob. I must admit I was a bit sceptical. Did you have the helmet on when you fired it up.?

Yep.....didn't wan't Thomas's friends to see my red face if it blew up.............

.

[woodyracer]

i should of worn my helemt when i binned my bike on the drive-way in the wet.........

[bucketracer]

.
a quick push and it started right up.........starts real easy......it even idles.........hows that. :banana:........

.

Starts easy and idles, two things that I didn't think it would do well, congrats on a real novel idea that's past it's first test with flying colors.

[SS90]

OK,, well done so far Teezee..... I too didn't expect it to idle so well!

The "flat spot" however, I expected (and I guess you did too).

We have discussed the inlet resonance etc neigh on a year ago...... I suspect we will be back to that.

how much "stand off" (amount of fuel/oil mixture) is coming out the carb when you are in the "flat spot" you mentioned?

Looking at your picture, I was making the assumption that the "wonderful gloss" you new engine had looked a little like it was caused by the "stand off" spraying over the engine.

Am I wrong in this assumption?

If it is though, no jetting will fix that, only finding a solution to the resonance this plenum has.

Nice legs by the way!:drool:

[TZ350]

How did I get such a "wonderful gloss" on my legs and would I be "stand off" ish if you made an assumption? Ok I knew it was a mistake to be in the photo’s...:laugh:

No the gloss on the engine is from the new paint, didn’t run the bike long, just up and down the drive once, to many people about watching.

It was satisfying to see them scatter as I approached on the return run, :scooter: it was like chasing chooks.

I hope to get a good look at it tomorrow night, when I will have time to figure if the flat spot is throttle position or rpm related.

[richban]

I am starting to get my head around your idea more. What I don't understand is the blow off valve! If it opens up when a strong pluse wave is sent through would that not defeat the volume calculations. What does it do. I was reading back and can't find the reason for it. I might be missing something obvious here (happens quite a lot) but what does it do?

[F5 Dave]

I can't see the pressure being enough to open it even if there wasn't a convenient hole at the front of the cases, it would have to be a hella amount of gas inertia to overcome just backflowing out the carb, it isn't a diode.

[richban]

I can't see the pressure being enough to open it even if there wasn't a convenient hole at the front of the cases, it would have to be a hella amount of gas inertia to overcome just backflowing out the carb, it isn't a diode.

Still don't understand why its there.

[F5 Dave]

Well clearly this is going to be more efficient than a turbo on full boost, so when it gets to about 14psi it will have to release the pressure so you don't get detonation, + the gearbox is probably only rated to 36hp.

[richban]

So you don't know ether!

[F5 Dave]

I was under the impression it was there for looks.

[Yow Ling]

I was supprised the valve cover wasnt made from copper with extra finning on top.

Isnt it there to stop the cases bulging .out after the explosion ?

[Buckets4Me]

I am starting to get my head around your idea more. What I don't understand is the blow off valve! If it opens up when a strong pluse wave is sent through would that not defeat the volume calculations. What does it do. I was reading back and can't find the reason for it. I might be missing something obvious here (happens quite a lot) but what does it do?

you guys are funny
it's there just incase it all goes boom
then the boost pressure will be a tad more than 14 psi
and we dont want it to reck the cases
so something has to go pop

give you three guess why his leg has no hair on it

[Buckets4Me]

I was supprised the valve cover wasnt made from copper with extra finning on top.

Isnt it there to stop the cases bulging .out after the explosion ?

yep you got it in one
go buy yourself a chocklate fish

as for the copper cover I think he is off to the scrap guy this afternoon

[TZ350]

Isnt it there to stop the cases bulging .out after the explosion ?

Yep that's it exactly.............

[TZ350]

What I don't understand is the blow off valve! What does it do. I was reading back and can't find the reason for it.

Thank you for your interest in my project.

The blow off valve is there because there are any number of reasons that a 2-Stroke engine will back fire, not all of them happen when the carb is wide open......

having the CDI discharge when you turn it's power off is one of them....

"BANG"....:shit:....fawk...think I just shit myself...is better than a backside full of shrapnel..:doctor:

.

[richban]

Yep that's it exactly.............

there are any number of resons that a 2-Stroke engine will back fire, not all of them happen when the carb is wide open......

having the CDI discharge when you turn the power off is one of them......:shit:

Will you screw it down tight now it is going?

I spent this afternoon playing with intake length and airbox volumes on my bike. I had 4 different trumpet lengths to try 16mm 35 60 and big old 120mm the engine would not run past half throttle with the 120 and the 60. The 35 seemed to work ok but had some reversion around 3/4 throtle, the 16mm was the ticket as expected. The calculations matched the practical design. But what surprised me was that the difference in engine performance with such a very small volume / length change. Then I put a 1 liter airbox on it and back to square 1. Trying a 2 litres tomorrow night.

[TZ350]

Interesting to watch your progress with the intake and how such a small change in length makes such a real difference

[TZ350]

Will you screw it down tight now it is going?

No no...just tight enough to keep the pressure in, lose enough to protect the motor from backfires...a bit of try and see

Might use a better looking boy racer blow of thing later.

[richban]

Interesting to watch your progress with the intake and how such a small change in length makes such a real difference

I think we are chasing the same thing Peak torque at 12000rpm.

[bucketracer]

The compromise in plenum volume is as follows:

A larger volume leaves more available air to the engine within its reach, and so long as this air can be replenished in time through the intake system, then the engine never has to work hard to get intake air because there’s always enough of it sitting there in the larger plenum.

As the plenum volume gets smaller, it becomes easier for the engine to rapidly consume all of the air in the plenum and thus it would have to spend a lot of effort (after the initial draw of air) trying to suck air in all the way through the entire intake system to stay alive.

The problem with a larger plenum is that it hurts throttle response. Throttle response is very much affected by throttle pressure (or in other words how fast the engine can consume all the air in the plenum and create a significant amount of vacuum in the manifold to draw in fresh air). The smaller the plenum (or smaller the runners), the higher the gas velocity, the faster the pressure drop, the sooner the new air rushes in, the faster the throttle response.

This usually leads to an oddball design by most OEM’s of an oversized plenum wit h a smaller throttle body and runners to try to boost gas velocity, or an undersized plenum (that will be consumed faster for better response) but with a larger throttle body that will not bottle neck the engine as it tries to pull in more air from the outside to stay alive at higher flow demands at higher rpms.

http://www.superchargerperformance.com/aftermarket-supercharger-performance/intake-manifold-design

[Henk]

OK going out on a limb here and proposing something that is probably idiotic and definitely stretches the rules as far as they can go.
Would it be possible to feed the plenum with a CV carb as big as you like with the butterfly locked at wide open or removed so that the metering is controlled entirely by the slide and vacuum in the plenum, then put a legal sized choke in the plenum feeding into the cases controlled by the throttle cable.
Not sure how you would control the valve in the plenum in such a way that there is no massive air leak causing a possibly fatal lean condition. As I said, probably idiotic.

[richban]

OK going out on a limb here and proposing something that is probably idiotic and definitely stretches the rules as far as they can go.
Would it be possible to feed the plenum with a CV carb as big as you like with the butterfly locked at wide open or removed so that the metering is controlled entirely by the slide and vacuum in the plenum, then put a legal sized choke in the plenum feeding into the cases controlled by the throttle cable.
Not sure how you would control the valve in the plenum in such a way that there is no massive air leak causing a possibly fatal lean condition. As I said, probably idiotic.

Just change the rules.

[TZ350]

Would it be possible to feed the plenum with a CV carb as big as you like........ so that the metering is controlled entirely by the slide and vacuum in the plenum, then put a legal sized choke in the plenum feeding into the cases

CV carb opens in proportion to the vacuum in the plenum, self adjusting, yes that is interesting, thanks Henk....

I will hold onto that idea, it could become usefull, a plan "B".

[TZ350]

This gives me hope, I estimate, my plenum is five times the engine capacity.

"30 years ago not much was known about the relevance of plenum volume although it was generally considered that it should not be too large or responsiveness would suffer, which is still true. It is now known that in a tuned, single intake, plenum induction system, top end power increases with the volume of the plenum. Ten times engine capacity would not be too big - indeed bigger still would be better, though rather impractical."

From http://www.jagweb.com/aj6eng/technics.php

This article also points out that for a forward facing intake, at 150mph the air pressure is 0.35 psi, so not much supercharging effect to be had from pointing the carbs intake into the wind.

[TZ350]

The plenum chamber past another test today, we had our first major backfire without any engine damage, the blow off plate did its job.

With some jetting changes I was able to improve the carburation. With some more work I think I will be able to dial the carb in and get it all running properly.

Everything has had to be richend up compared to the conventional setup. Interestingly it does not spit much fuel out unless you give it more throttle than it needs then it gets the Blllarrrs and spits fuel 450mm, yes, we measured it.

I also think that for a motor that peaks at 9500 that using a std GP125 disk valve for an inlet timing of 145/60 205 duration with a 34mm port diameter is too wild. I may have to make some milder rotary valve disks.

I have found you can’t give this engine a big fist full of throttle, you have to dial it on carefully, just like a 70's TZ. But it takes off on a ¼-1/3 throttle with the same enthusiasm it used too before on full throttle. So by the time I can get it onto ½-3/4 throttle the end of the drive is coming up faster than I like.

There are still a few flat spots in the carburation but I expect to get them dialled out ok. The bike is still on Taupo gearing and even holding it in 1st gear, and using 1/3 throttle it’s just to fast for the drive. To finish setting up the carb I will have to change the gearing or find a quiet road some where I can get it onto full throttle and revved out.

It might just be the “excitement” talking, but I recon it’s faster than before.

I am sure looking forward to "Dyno Time".

[TZ350]

Just change the rules.

NOoo...no no no ...we are so enjoying the challange of the 24mm carb restriction, and now think we have cracked it. Water cooling would be nice, although we think we have a good handle on the cooling issues too.

No rule changes, unless its that FXR's are only allowed one front fork leg.

[Buckets4Me]

I will hold onto that idea, it could become usefull, a plan "B".

dont you mean plan "R" ????
you tried plan B some time ago
I think the copper was plan"K"

[Henk]

No rule changes, unless its that FXR's are only allowed one front fork leg.

Right I'm off to design a single sided, carbon fibre, hub center steering setup as a contingency plan. might as well make it 2wd while I'm at it.
Actually that would be cool, shame I don't have the talent.

[Pumba]

Now there was a photo on the FXR site that would be apropriate about now but buggered if I can find it. Bust just imagine how easy the changes to wets would be.

[jasonu]

Just change the rules.

Or run a water cooled 100cc...

[TZ350]

It's a slide show, downlodable PDF, about the theory of 4-stroke inlet tuning, check the "rule of thumb" second to last slide.

For 2-strokes just half the runner length. www.not2fast.com/gasflow/Lecture08.ppt

Maybe more for 4-strokes but lots of interesting stuff here:- http://www.not2fast.com/

[bucketracer]

Or run a water cooled 100cc...

I suspect Dad thinks it's too easy. ;) and is married to the idea of a 125 air cooled

[bucketracer]

Abstract

Naturally aspirated racing engines have tuned intake systems and can now achieve volumetric efficiencies in excess of 125% and peak engine speeds in excess of 18,000 rev/min.

Engines designed for single seater racing commonly dispense with the intake manifold and its convoluted and restricting flow path preferring single lengths of pipe feeding each cylinder separately.

An investigation into the intake process on a single cylinder racing engine has shown that inertial ram effects make a strong contribution to the intake process at high engine speeds whereas acoustic resonance effects are more important to the rather weak wave action that occurs at low engine speeds.

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WM3-49NVFYW-9&_user=10&_coverDate=04%2F06%2F2004&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1186351668&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=a9dee0e796531ce02e8eeba5bf0b4fe2

[bucketracer]

Interesting dyno results here:- http://www.factorypro.com/dyno/true1.html

Those big hp Honda RS125's measured on a DynoJet are really only making 35 or so and a stock one 30 - 32 rwhp.

A big database of all the bikes imaginable, your bike will be there.

[craisin]

So if there no advantage at pointing the carb forward
Oh right its dust injection off the front wheel

[TZ350]

No….it’s there because it looks good, it’s all about individuality don't you know! If you have a great carb, why hide it? It looks just the bis... with all that copper and it was also a convenient place to attach it to the engine.

[=cJ=]

Couldn't you have just 'leccy taped it to the subframe or somewhere it won't get so dirty? :p

I'm following this thread with quite some interest though :)

[Yow Ling]

There are other awesome bikes with forward facing carbs, TZR250 3MA , some TZ500's. When I had a forward facing exhaust , I was getting lots of advice about the extra backpressure etc, that adventure solved itself as it kept falling off because of the vibration. I think the extra pull from the enoumus suction of that engine will give you a huge advantage , hell the suction may even affect other nearby bikes.

[craisin]

yeah right if it was a multi cylinder i would understand your choice in induction systems:laugh:

i guess losing some volume off your chamber would be easy

[TZ350]

There are other awesome bikes with forward facing carbs, TZR250 3MA , some TZ500's. When I had a forward facing exhaust , I was getting lots of advice about the extra backpressure etc, that adventure solved itself as it kept falling off because of the vibration. I think the extra pull from the enoumus suction of that engine will give you a huge advantage , hell the suction may even affect other nearby bikes.

For me its all about style, nothing to do with performance........I have a real bling carb and want to show it off.....next I am going to learn how to hang of the side of my bike while cornering and look all fancy......:laugh:.....style is everything......everything important that is...

Watch out for a real bling copper vacuum cleaner coming to a race track near you soon

[jasonu]

[QUOTE=Yow Ling;1129629914]There are other awesome bikes with forward facing carbs, TZR250 3MA , some TZ500's.

The 2010 YZ450 has the induction on the front side and a rear exhaust but I guess you lot in NZ won't see it for another couple of years...

[F5 Dave]

Interesting dyno results here:- http://www.factorypro.com/dyno/true1.html

Those big hp Honda RS125's measured on a DynoJet are really only making 35 or so and a stock one 30 - 32 rwhp.

A big database of all the bikes imaginable, your bike will be there.

Yeah that is all very well, but there needs to be some sort of comparrision & Dynojet has become the std as it has been the most popular & is equivilent to all the tests you read in bike mags etc.. Several dynos are more inflated that Dynojet, a local one is 15% both by rumour & my own comparison & another is supposed to be more than that.

An std customer RS125 on a dynojet does put out about 32-35hp. the earlier ones to the lower end of the scale, the 94s were good & the 95s slumped a little but have gotten progressively better so a pretty hot one is probably 40 until you start spending the big bucks & gas etc. A few years back the GP level ones were reputably hitting 50 & I suspect the factory Aprilias etc are tweaking on a bit now, but it has to be near the limit on the gas they can run.

[TZ350]

Ok...I may never live this down, :doh: but my arse has been saved by an FXR.

I have purchased a real good looking pod filter from FXR150.co.nz for my plenum carb. The filters come in 47mm and 50mm fitments and look just the biz for keeping rocks and crap out of my forward facing carb....:2thumbsup

I will be able to finish dialling in the carburation when I get the filter then its of to the dyno.

[Buckets4Me]

I have purchased a real good looking pod filter from FXR150.co.nz for my plenum carb.

now you are asking for trouble

[F5 Dave]

They look just like K&Ns. Bet they were somewhat cheaper & probably just as good, made in the same factory etc etc. . . . Or so the story goes until you back to back test them on the dyno. Those Emgo ones lose quite a bit of hp compared to K&N.

[TZ350]

They look just like K&Ns. Bet they were somewhat cheaper & probably just as good, made in the same factory etc etc. . . . Or so the story goes until you back to back test them on the dyno. Those Emgo ones lose quite a bit of hp compared to K&N.

Have you done a back to back comparison yourself, has anyone done a trial? if not then its something I might try. In the mean time the www.FXR150.co.nz filters look pretty good and they will do the job while I run the plenum through its "proof of concept" trials.

.

[jasonu]

Have you done a back to back comparison yourself, has anyone done a trial? if not then its something I might try. In the mean time the www.FXR150.co.nz filters look pretty good and they will do the job while I run the plenum through its "proof of concept" trials.

.

I know Dave Dip (a long time ago) did back to back dynojet 100 runs and found a simple wire mesh rock screen over the intake of the otherwise open carb significantly reduced HP. (sorry for divulging one of your secrets Dave)

[F5 Dave]

A friend who used to own the dyno did some back to back tests, Emgo vs K&N are the ones I remember. As usual anything untested is untested.

[richban]

I will be able to finish dialling in the carburation when I get the filter then its of to the dyno.

I will be very interested in the results will you do a run with and without the filter. I had some interesting results from the intake testing at Manfield. I am back to running straight from the carb bell-mouth. The 16mm trumpet I tested gave me quite a flat 3/4 to full throttle feel and (seamed) like less power. It did have a green ring that developed 5 mm out into the trumpet from the avgas. So I figure it is very close. I will have my bigger volume 28mm carb body finished soon so a little more volume might be just what it needs. Or not.... They call exhaust design a black art ... I think intake is just as frustrating. And of course change one and you need to look at the other. Speaking of exhausts I have 2 revers-cone megaphones to build. That should open up another can of worms all together....

[TZ350]

Hi Rich, interesting to see how your getting on, interesting carb idea.

For us the game plan is; the new air filter should arrive this week, then we can take the "Flying Vacuum Cleaner" to MtWelly for Saturdays practice.

If we can get it to carburate satisfactorily then the following week its off to the dyno at Johns place with Speedpro to test our bikes, if he hasn’t got sick of waiting and beaten me to it by then.

Untill then here are few pictures of a 1970's water cooled 4 cylinder rotary valve 125cc Yamaha road racer, 42 RWHP at 18,000rpm photoed by Chambers at the clasic meet last weekend.

[Bert]

I know this thread is well beyond this...
but I though it might be useful; if it hasn't been posted before.

http://ypvsbox.free.fr/pipedesigner_en.html

and this

http://www.gifford.ca/hydroform.html

[TZ350]

Thanks for the link Bert, looks interesting.

More on trying to get the plenum sorted. I fitted short track gearing to reduce my speed in the driveway and had another go at the jetting, things are starting to come right with a 180 main jet, the bigest I have, it was about 130 before. The plenum seems a bit prone to load up with fuel making jetting with short test runs in the drive way difficult.

The motor has a bad case of the blarrrrs and then picks up very strongly, it reminds me of when I tried a GP125 disk in a GP100. The 100 would have the blarrrrs then hit real hard and then not rev out. The 100's inlet was out of sink with the rest of the motor.

Because of the big inlet on the plenum set up, even with the std GP125 rotary disk the inlet port time area is excessive for max power at 9,000 so I will try reducing the inlet duration tomorrow by fitting a GP100 rotary disk and also get a few more bigger jets to try.

There appears to be no standoff in front of the carb when its driving well but spits a bit of fuel out when its got the blarrrrrrs. Once or twice I got a good run,changed into second and gave it a handfill, the beast sure felt strong, although a little rich.

It starts so easy and pulls away like a dream although not very crisply, and I think I will be able to fix that.

Things are looking good, it hasn't blown up yet and might actually work.
.

[TZ350]

Changed the rotary valve today, timing is now 135/40 opens 135 BTDC closes 40 ATDC, 175 duration, down from 205. Port window area 9 cm#. The big surprise was that when we took the cover of, there was a good ½ cup of raw petrol mix sloshing around in the bottom of the plenum.

When the motor is pulling ok there is no discernable spit back through the carb, so I am not sure where this excess fuel is coming from, dropping out, being spat out of the engine, choke stuck on, who knows. But I was right when I thought it was getting loaded up.

With the new inlet timing the thing runs better but a pool of fuel still develops in the bottom of the plenum……..

Pic-01 bike ready for open-heart surgery
Pic-02 Plenum (after I dried it out)
Pic-03 with the side cover off
Pic-04 new and old rotary valves
Pic-05 Thomas had the thing apart and back running in about 45 mins, the other guys are straightening Chambers bike up after he and Avalon took turns throwing it down the road at Taupo.

Some days I feel more hopefull than others that I will get this thing to run properly. :crazy:

[F5 Dave]

So the calorific value of petrol is 45.8 MJ/kg and a 1/2 cup is say 125cc, if it was water that would be ~ 6 megajoules of energy, but petrol is a bit lighter.

How big an explosion is that? There must be some easy conversion to TNT, the one I found was dicky & I lost interest:wacko:

[TZ350]

So the calorific value of petrol is 45.8 MJ/kg and a 1/2 cup is say 125cc.......How big an explosion is that? :wacko:

Thankfully not very big, the petrol still needs an oxidiser and 875cc of air doesn't go far..:sweatdrop..thank God, its less dangerous than your average petrol tank...........but I won't be running this setup with nitro, not even for shits and giggles.....

[richban]

When the motor is pulling ok there is no discernable spit back through the carb, so I am not sure where this excess fuel is coming from, dropping out, being spat out of the engine, choke stuck on, who knows. But I was right when I thought it was getting loaded up.

:


You could always make a drain out of your plenum so you could measure the excess fuel. Time / cc's collected. Then change the volume and see if you get less. Might give you some gauge of efficiency.

[TZ350]

You could always make a drain out of your plenum so you could measure the excess fuel. Time / cc's collected. Then change the volume and see if you get less. Might give you some gauge of efficiency.

I have fitted a carb main jet as a drain/air bleed and also thought of using the pumper part of a carb from a weed eater to pump the surplus fuel back to the tank. And I also have plans about how to reduce the volume of the plenum from it's current 1 litre volume in a graduated way. But had not thought of measuring the excess fuel as an indicator of how air flow has change inside the plenum, that’s a good idea, I will try it.

[Yow Ling]

I have fitted a carb main jet as a drain/air bleed and also thought of using the pumper part of a carb from a weed eater to pump the surplus fuel back to the tank. And I also have plans about how to reduce the volume of the plenum from it's current 1 litre volume in a graduated way. But had not thought of measuring the excess fuel as an indicator of how air flow has change inside the plenum, that’s a good idea, I will try it.

if you filled the bottom of the plenum with resin so the re was nowhere for the fuel that dropped out of suspension to puddle that might mean you could go bit leaner on your mains. the extra fuel you are feedin it is probably just to account for what goes MIA . still give you plenty of volume in your plenum just nowher to store all the extra gas

[Buckets4Me]

do we have to wear fireproof suits ???
I think I might just go out and get one anyway

brings new meaning to burning off the oposition
or toasting them
or blowing them away lol

dont upset TZ350 he may FLAME you

HAHAH ha

ok I'm off to do some work around the house now
see ya tomorow

[bucketracer]

Cunning old TeeZee is not stupid......Buckets4me is going to be the "flying vacuum cleaners" test pilot tomorrow........;).....

I am going to watch from the top of the hill.

[TZ350]

Off to Mt Welly today to test the Vacuum Cleaner, showers, forward facing carb, slippery track Ohooooo what joy. :wacko:

Pic is of the Keihin jetting guide for the PWK carb...

[Buckets4Me]

Off to Mt Welly today to test the Vacuum Cleaner, showers, forward facing carb, slippery track Ohooooo what joy. :wacko:

Pic is of the Keihin jetting guide for the PWK carb...

at least I'm less likely to burn to death if it's raining

what do I do Stop drop and SCREAM ?

[Muzzab]

at least I'm less likely to burn to death if it's raining

what do I do Stop drop and SCREAM ?

I hope you guys are taking a video camera, it will be better with sound!!

[Sketchy_Racer]

This Plenum thing is very very interesting!

Kind of an odd question, but has it been thought to put a slide on the intake to the motor and leave the carb completely open all the time? or maybe have a cable split and have two throttle slides opening, one on the motor intake and one on the carb??

[TZ350]

Links from the last ten pages, other link collections can be found on pages 80, 90, 100, 110 120

This is my favourite photo of Avalon, at the BOB,
https://secure.sportzfotoz.co.nz/popimage.php?imageid=45555

Tuning Keihin Carbs:-
http://www.carbparts.com/keihin/needles_tuning/keihin_tuning.htm

The jet size problem, interesting info on jets posted by SS90.
http://rd500lc.free.fr/technics/jet_size_fr.htm

All sorts of info on tuning carbs here:-
http://www.sudco.com/mikuni.html

Some interesting info on hydroformed expansion chambers from Bert.
I though it might be useful; if it hasn't been posted before.
http://ypvsbox.free.fr/pipedesigner_en.html
and this
http://www.gifford.ca/hydroform.html

A digital/programable DC-CDIP 2 Race 2-Stroke IgniTech ignition, there are also units for 4-Strokes, they can be purchased from The Two-Stroke Shop or directly from IgniTech. http://www.ignitech.cz/english/aindex.htm

The setup info was found on the Two-Stroke Shop www.twostrokeshop.com site.

This is about the latest RACE Ignitech and our ignition systems: http://www.twostrokeshop.com/ignitech_race.htm

Here is an article showing how to modify the RZ hardware to allow use of the Ignitech twin cdi module, eliminating the wasted spark system and giving full control over all electronic functions. http://www.twostrokeshop.com/ignitech.htm “.

For 2-strokes just half the runner length.
http://www.not2fast.com/gasflow/Lecture08.ppt

Maybe more for 4-strokes but lots of interesting stuff here:-
http://www.not2fast.com/

Resonant Airboxes: Theory and Applications:-
http://motorcycleinfo.calsci.com/Airboxes.html

The volume of the plenum:-
http://www.jagweb.com/aj6eng/technics.php

More on Plenums from:-
http://urbanracer.com/articles/anmviewer.asp?a=3344&z=38

All you want to know about physics and resonance
http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.html

Automotive Calculators, lots of fun things to play with:-
http://www.wallaceracing.com/Calculators.htm

Some theory to help you in putting it all together:-
Power…………………. http://www.bgideas.demon.co.uk/tmanual/Tm_Ch1.pdf
Breathing & Induction.. http://www.bgideas.demon.co.uk/tmanual/Tm_Ch2.pdf
Combustion…………... http://www.bgideas.demon.co.uk/tmanual/Tm_Ch3.pdf
The Exhaust System…. http://www.bgideas.demon.co.uk/tmanual/Tm_Ch4.pdf
Camshafts…………….. http://www.bgideas.demon.co.uk/tmanual/Tm_Ch5.pdf
Ignition Systems……… http://www.bgideas.demon.co.uk/tmanual/Tm_Ch6.pdf
Turbo or Supercharger.. http://www.bgideas.demon.co.uk/tmanual/Tm_Ch7.pdf
Engine Reliability…….. http://www.bgideas.demon.co.uk/tmanual/Tm_Ch8.pdf

Interesting dyno results here:-
http://www.factorypro.com/dyno/true1.html

[TZ350]

has it been thought to put a slide on the intake to the motor and leave the carb completely open all the time? or maybe have a cable split and have two throttle slides opening, one on the motor intake and one on the carb??

This is a good idea, I am not sure how to work it, but reducing the port size into the motor some how at lower revs to get the gas velocity up, would probable overcome the fuel blowback problem.

[TZ350]

Testing at MtWelly was difficult on the wet track, there was not a lot of traction, open the throtle and the back wheel would just spin up. Then the motor would backfire as it climbed into over rev.

Why some motors do that, pop back through the carb when they have revved past peak power I don't know but two of Team ESE's motors have regularly done it on the dyno while the others dont?

After quite a few backfires the seal on the blow off valve gave up, ending the days testing. We haven’t got the thing working completely smoothly yet, but it looks like it will work.

It has some kinks to iron out, but it does run, didn't blow up and shows promise. I am looking forward to getting the beast onto a dyno soon to see if the gains make it worth persevering with and developing it further.

I had a look around the pits and there were only 4 2-strokes about 10 or 12 FXR's 3 CB125T's and a CBR. I think without the FXR's in buckets, buckets would be fading away, up here anyway.

[Yow Ling]

This Plenum thing is very very interesting!

Kind of an odd question, but has it been thought to put a slide on the intake to the motor and leave the carb completely open all the time? or maybe have a cable split and have two throttle slides opening, one on the motor intake and one on the carb??

I think there may be a downside to this, the carb is designed to give different mixture strenghts at different combinations of airflow and throttle position, running WOT will give correct fuelling at high rpm/power and then with low airflow through the venturi at lower speeds will screw up all the benifits gained from having a needle and needle jet.

Might work with a CV carb, as it adjusts to the engine load

[bucketracer]

Or you could adjust the tuned length of the inlet port so the out of resonance point (the blarrrs) are moved to somewhere else...........

[SS90]

Or you could adjust the tuned length of the inlet port so the out of resonance point (the blarrrs) are moved to somewhere else...........

Or fit a reed valve.

[F5 Dave]

Yeah but a reedvalve into a rotary input negates the benefit + he still needs that bit to be the 24mm restriction.

[SS90]

Yes, but with-out the Reed Valve, the Plenum will never work, jetting up just softens the resonance problem/reduces power.

There is clearly an intake tract resonance issue here.

There are so many people before that have tried to compensate for problems that have found that larger jets "improve" things, only to find that, in the end, no jet in the world will fix things.

simple logic/experience says that the jet sizes he is using defy common sense

125cc Two stroke engines with pressurised airboxes producing over 40 PS and achieving in excess of 200KPH don't use jets the size Teezee is currently using.

I don't think the Plenum will be a worthwhile effort.

Never seen a 125GP bike with one, and that is always a good place to look for inspiration.

[TZ350]

Yeah but a reedvalve into a rotary input negates the benefit + he still needs that bit to be the 24mm restriction.

Hi Dave my carb is 24mm, the duct from the plenum into the engine is 34mm, the theory being that at WOT the carb flows all the time and is able to refill the plenum to at least atmospheric pressure by the time the motor takes another gulp. I figure a 24mm carb can flow full time as much as a 34 that is only sucking for half the time. If I can get a beneficial resonance through the carb going I have considered a read valve after the carb to help pump the plenum up to higher than atmospheric pressure.


Yes, but with-out the Reed Valve, the Plenum will never work, jetting up just softens the resonance problem/reduces power.

There is clearly an intake tract resonance issue here.

There are so many people before that have tried to compensate for problems that have found that larger jets "improve" things, only to find that, in the end, no jet in the world will fix things.

simple logic/experience says that the jet sizes he is using defy common sense

125cc Two stroke engines with pressurised airboxes producing over 40 PS and achieving in excess of 200KPH don't use jets the size Teezee is currently using.

I don't think the Plenum will be a worthwhile effort.

Never seen a 125GP bike with one, and that is always a good place to look for inspiration.

Hi SS you make a lot of good points, thank you. I will work through them so you can see my thinking.

A plenum, “Never seen a 125GP bike with one”, probably because they are not restricted to 24mm like I am, so don't need to look at different ways of doing things.

The reason for the plenum is so that the motor can suck through a 34mm straw in large gulps from a big reservoir of air/fuel at atmospheric pressure instead of trying to gulp outside air through a restrictive 24mm one.

“I don't think the Plenum will be a worthwhile effort.” You could be right, or wrong, and now that the engine pulls well on WOT, I am keen to get the bike onto a dyno to see if there is any real gain.

“125cc Two stroke engines with pressurised airboxes producing over 40 PS and achieving in excess of 200KPH don't use jets the size Teezee is currently using.” “simple logic/experience says that the jet sizes he is using defy common sense”

Those motors aren’t using a plenum between the carb and engine…….At the moment I put my bigger jet requirement down to the fact, that when my plenum motor is pulling there is no discernable standoff in front of the carb.

Unlike other motors where at resonance the air bounces back and forth in the inlet tract at least three times, picking up fuel each time it passes the jet, I think the air flow through the plenum carb is all one way, so it has to pick up all its fuel in one go on the way in, hence the bigger jet.

“There is clearly an intake tract resonance issue here.” The resonance issue is with the 34mm tract from the motor into the plenum.

When the inlet duration was 205 degrees the motor would suffer a bad case of the blarrrrs before hitting hard. With the duration reduced to 180 degrees the blarrrs have significantly decreased but the port/time/area is still excessive for an engine that makes max power at only 9000 rpm.

I would have to reduce the inlet duration to 160 degrees (135/25) to get the correct inlet port/time/area but this requires making a new rotary valve and that is a job of work in itself.

Another problem was, that the 34mm inlet tract into the engine had a tuned length more suitable for 11,000 than 9,000 rpm so we are changing that now.

The blarrrs or reversion at the bellmouth of the 34mm inlet tract, I believe is associated with the inlet closing point and tuned length. From the testing we have done so far, we know its not going to blow up. So all of this gives me hope that we can get on top of the resonance (blarrrs) problem and it will all be a big succes.

Yes, in the end it might not work, but I don’t think we have played it all out yet, and it performs better every day.

I remain optimistic.

[jasonu]

QUOTE I would have to reduce the inlet duration to 160 degrees (135/25) for the correct inlet port/time/area but this requires making a new rotary valve and that is a job of work in itself.

Surely makeing a new disk valve would be the eaisest thing on your plate right now. That is the beauty of the disk valve motor, if you cock up a disk, unbolt it and try another.

[TZ350]

Surely makeing a new disk valve would be the eaisest thing on your plate right now. That is the beauty of the disk valve motor, if you cock up a disk, unbolt it and try another.

Yes, its easy to increase the duration by cutting an existing disk but reducing the duration to something less than std requires putting metal back, it means drawing one in CAD then having it lazar cut, and getting the fine teeth with their little radiuses cut precisely right to match the driving dog, I have found to be a bit of a trick.

[bucketracer]

Hi TeeZee from reading recent posts, I don't think people have quite grasped the concept behind your plenum chamber.

[bucketracer]

Yes, but with-out the Reed Valve, the Plenum will never work,

Why.......

[Buckets4Me]

Why.......

it was working ok when I rode it :)

just needed to behave better thats all (much like all good fast 2 strokes)

[SS90]

Why.......

OK, think of it this way, Teezee has just made some good points in relation to his continued optimism, and I will in no way intentionally discourage him, and indeed be glad to be proved wrong.

But, from all the explanations Teezee has given regarding his "blarhhhrrr's", he has indicated that the way to (drastically) reduce this is by 1) reducing the inlet area and 2) increasing the manjet size.

OK cool.

When the "Blarrrrgghhrs" come on, there is significant standoff coming out the carb.

This should simply not happen.

This would indicate that, like Teezee said, essentially the carb (which, can of course work both ways) is "pusing the fuel out the wrong way"

A reed valve would stop this.

Although, this indeed my cause the plenum to overfull, and his "blowoff valve" may indeed be worked even harder, ..........particularly if the inlet timing is reduced.
Kind of like stuffing up your inlet timing on a Piston ported two stroke.

The dyno is the correct way to go for sure, because as Teezee has pointed out, he needs to see if there actually any gains, which is all he needs to kow if he is going in the right direction.

I should watch Buckets4me's youtube video now, I would like to see how it sounds.

[SS90]

I should watch Buckets4me's youtube video now, I would like to see how it sounds.

Bastards!:o

[Buckets4Me]

I should watch Buckets4me's youtube video now, I would like to see how it sounds.

wish I had some
maby next time I will arange it
or if I get to go to the dyno I may take the video camera

[jasonu]

Yes, its easy to increase the duration by cutting an existing disk but reducing the duration to something less than std requires putting metal back, it means drawing one in CAD then having it lazar cut, and getting the fine teeth with their little radiuses cut precisely right to match the driving dog, I have found to be a bit of a trick.

I didn't think of that.
Maybe you could cut a sliver from another disk, clamp the whole thing to a copper plate and CAREFULLY Tig weld the 2 together. There used to be a product called magic mud available. It is a clay like substance you put right near where you are going weld as a heat sink.

[TZ350]

But, from all the explanations Teezee has given regarding his "blarhhhrrr's", he has indicated that the way to (drastically) reduce this is by 1) reducing the inlet area and 2) increasing the main jet size.


I probably didn't explain the symptoms very well, or maybe I am more familiar with them now.

I don't see the blarrrs as being related to the main jet.

The blarrrs are RPM related, around 5,000 is my guess.

When the motor is in the blarrrrs it is possible to hold it there by opening the throttle to wide.

Reduce the throttle and the motor will slowly work its way through the blarrrs

or by carefully blipping the throttle at 3-4,000 rpm I could zing the motor past the blarrrs.

With the jets I had to hand I quickly got the carburation so that the motor started, idled and pulled strongly up to half throttle, then it fell flat on its face.

It took a few days before I had found/purchased the right main jets, now it pulls strongly at full throttle too, so long as the rev's are above 6,000 or so.

I think the carburation is pretty well right but this is not a setup that will take a big handfull of throttle and I don't expect that will change.

In dealing with the blarrrs I see the issues as now being port/time/area and tuned length of the 34mm induction tract.

I started this to try and emulate the big carburation of the unrestricted 100's totally forgetting they were being reved to 12,000 rpm.

I had also brought into the "Shorter is Better" inlet tract theory.

My current port/time/area is good for the big rev but totally excessive for 9,000. I see this as the source of my blarrrs problem.

Along with an induction tract that is to short.

[TZ350]

Ok. made a few changes and we have now beaten the blarrrs....

[Buckets4Me]

Ok. we have now beaten the blues....

that good for you
now keep taking them pills will ya
did you make a smaller rotary valve ??

[koba]

Ok. we have now beaten the blarrrs....

Did you use a big stick?

[TZ350]

did you make a smaller rotary valve ??

No. added 35mm to the inlet tract, now the tuned length, diameter and port/time/area are all in the same ball park.

If the plenum idea shows promise on the dyno, we will set about optimising everything.

While working through the issues, I just had to apply some logic and reasoning, and I knew it would come right.

When it was broken down into steps, I could see, that logicaly it had to work.

[Buckets4Me]

what day are you going to the dyno ???

[TZ350]

what day are you going to the dyno ???

Don't know, John is away on holiday......

[TZ350]

Did you use a big stick?

No. but if they come back I will wack em with a stick, the little bastards....

[bucketracer]

and indeed be glad to be proved wrong.

SS90, a happy day for you, with some logical reasoning Dad overcame the plenums blarrrs problem.

[SS90]

SS90, a happy day for you, with some logical reasoning Dad overcame the plenums blarrrs problem.

......... I look forward to a youtube video of the bike on the dyno, as well as a dyno graph.........

When I finish my latest exhaust design, I will do the same......

[TZ350]

......... I look forward to a youtube video of the bike on the dyno, as well as a dyno graph........I will do the same.......

So, if I show you mine, you will show me yours..:shifty:..........

I will be happy to look at the video of your results if you want, and the boys can bring a video camera along if they like. If my bike does anything exciting like catch fire or blow up they can put it on U-Tube.

A blowup or failure I am happy to laugh about, but if it goes real well on the dyno I might like to keep the exact results to myself as a suprise for Taupo...:D....or the BOB

[SS90]

So, if I show you mine, you will show me yours..:shifty:..........

I will be happy to look at the video of your results if you want, and the boys can bring a video camera along if they like. If my bike does anything exciting like catch fire or blow up they can put it on U-Tube.

A blowup or failure I am happy to laugh about, but if it goes real well on the dyno I might like to keep the exact results to myself as a suprise for Taupo...:D....or the BOB

No,no It's not some morbid desire to see a failure, it's more that I would like to see/hear what your bike sounds like running up on the dyno.......I don't see the point in keeping your power figures secret.... either ya win, or ya don't,and this has been "quite well hyped" ( not in a negative sense)....

I am certain I am not the only one who wants to see a power graph/dyno run video:blip:

[Muzzab]

I am certain I am not the only one who wants to see a power graph/dyno run video:blip:[/QUOTE]


That's for sure, I have no idea what you guys are talking about most of the time, but you can't lead us on then not go all the way. :buggerd:

[bucketracer]

Dad was out on a job so we had a bit of fun at lunch time, probably get our arses kicked later for fu..king around at work.

In the first moments of the clip you can see how easy it is to start from cold, and that there is no blow back from the carb.
The Magic Vacuum Cleaner 01 http://www.youtube.com/watch?v=YxiEo8cgopg

Warming it up before a bit of a blurt up the drive.
The Magic Vacuum Cleaner 02 http://www.youtube.com/watch?v=p4ef-WUO1Qs

[SS90]

The second one wouldn't load, but the first one sounded alright!

[Muzzab]

Good stuff!!

[SS90]

The second one wouldn't load, but the first one sounded alright!

The second one loads now, so what size main jet is it running now?

Teezee, can you post a few pictures of the entire system (with the cover removed), after the mods with the inlet tract length?

[Buckets4Me]

The second one loads now, so what size main jet is it running now?

Teezee, can you post a few pictures of the entire system (with the cover removed), after the mods with the inlet tract length?

it's just all open with a BIG bell mouth where the carb bolted to
look back a page or 2 and you will see it lying on the floor with the copers open
http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=196021&d=1265947716

[SS90]

But, we can't see how Teezee managed to fix the resonance problem by simply extending the inlet tract by 30 odd mm........ it looks the same as it did when it went "Blarggghhhhh"...... etc........ can we see a few pics?

Personally, I am amazed such a small change (just over 30mm) made such a big difference....... so much so, that I would like to see a picture of the whole thing.....it just does not match to my experience............. I mean just over 3cm fixed all these problems.........

I'm sorry, I am skeptical, and I am not alone in this.........

Perhaps Teezee himself could enlighten us all.

[TZ350]

Personally, I am amazed such a small change (just over 30mm) made such a big difference....... can we see a few pics?......


I used a 4-stroke inlet tract, tuned length calculator that I also posted a link to on page 130, to get a ball park figure then halved it for use with a 2-stroke, to get a starting point.

It worked out that I had to add about 35mm to the original setup http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=196020&d=1265947716 everything else is the same, no reed valve and the Keihin main jet is still 185. Should be able to post a new picture next week when I get back to work.

Yes its pretty stunning what a small difference can make...........

[TZ350]

But, we can't see how Teezee managed to fix the resonance problem by simply extending the inlet tract by 30 odd mm........ it looks the same as it did when it went "Blarggghhhhh"......

Personally, I am amazed such a small change (just over 30mm) made such a big difference....... so much so, that I would like to see a picture of the whole thing.....it just does not match to my experience............. I mean just over 3cm fixed all these problems.........

I'm sorry, I am skeptical, and I am not alone in this.........

Perhaps Teezee himself could enlighten us all.

Before the crankcase volume, the kinetic energy of the inlet gas column and inlet closing point wasn't in balance, now it is.

It all has to do with the balance between inlet tract length, inlet area, port closing point and the volume of the crankcase. It hinges around the kinetic energy of a column of air pushing into a chamber and compressing the air thats in there already.

The moving column compresses the chamber air like it is a spring until the increased pressure of the chamber air stops the moving column and then reverses it and then the compressed air in the chamber starts unwinding and pushes the column of air back out rapidly.

And in this way the air in the column shuttles back and forth, first filling and then compressing, and then being expelled again if the door has not been shut to keep it in.

In classical studies this activity is described by the Helmholtz’s Resonator http://people.seas.harvard.edu/~jones/cscie129/nu_lectures/lecture3%20/ho_helmholtz/ho_helmholtz.html.

But I find it easier to think of a large room, a door and a corridor filled with people rushing and pushing to get into the room. The room fills up and at some point the room will be packed to overflowing and some people will get pushed back into the corridor.

Causing a ripple effect back along the corridor to the entrance where some people will spill back out onto the pavement. Just like the air/fuel being ejected out of my carb during the blarrrs. So I needed to shut the door earlier or have a longer inlet tract to take advantage of the greater kinetic energy of the longer and therefore heavier moving column of air/fuel to pack the crank case for a bit longer before the rotary valve closed.

Its easy to see how having the weight of more people moving along a longer corridor will pack more people into the room and a wider corridor with a bigger door will do it more quickly and the greater weight of people in a longer corridor will pack the room more tightly. But whatever to get maximum room packing, the trick is to close the door before any people spill back out.

There will be a balance between the size of the room, the door, the corridor and the right time to close the door for maximum effect.

It’s the same for the crankcase volume, port area, inlet tract length and inlet port closing time, there is a balance point.

It’s a bit of a simplification but to do it justice it would take a lot of thoughtful writing that I don’t have the time or skills for.

And there has been a lot written about this already on the net and in books, mostly 4-stroke but with a little imagination and thought it can all be applied logically to 2-strokes.

So its all out there, and I have posted links to what I can find, you just have to go looking……and reading.....and thinking for yourself........and if you are so inclined, you can post links to any good bits you find for others to enjoy too, like I do.

As you can see from the video, your friends look like they are wrong or just havn't got there yet.

Unless they can explain why, don't listen to "nay sayers", negatives are two a penny especialy on the net.

Getting a plenum to work is about understanding and applying basic principles.

As you see, it can be done......:niceone:....so good luck with your own plenum project.

[Buckets4Me]

I'm sorry, I am skeptical, and I am not alone in this.........



HA HA HA now why am I not surprised

[SS90]

Before the crankcase volume, the kinetic energy of the inlet gas column and inlet closing point wasn't in balance, now it is.

It all has to do with the balance between inlet tract length, inlet area, port closing point and the volume of the crankcase. It hinges around the kinetic energy of a column of air pushing into a chamber and compressing the air thats in there already.

The moving column compresses the chamber air like it is a spring until the increased pressure of the chamber air stops the moving column and then reverses it and then the compressed air in the chamber starts unwinding and pushes the column of air back out rapidly.

And in this way the air in the column shuttles back and forth, first filling and then compressing, and then being expelled again if the door has not been shut to keep it in.

In classical studies this activity is described by the Helmholtz’s Resonator http://people.seas.harvard.edu/~jones/cscie129/nu_lectures/lecture3%20/ho_helmholtz/ho_helmholtz.html.

But I find it easier to think of a large room, a door and a corridor filled with people rushing and pushing to get into the room. The room fills up and at some point the room will be packed to overflowing and some people will get pushed back into the corridor.

Causing a ripple effect back along the corridor to the entrance where some people will spill back out onto the pavement. Just like the air/fuel being ejected out of my carb during the blarrrs. So I needed to shut the door earlier or have a longer inlet tract to take advantage of the greater kinetic energy of the longer and therefore heavier moving column of air/fuel to pack the crank case for a bit longer before the rotary valve closed.

Its easy to see how having the weight of more people moving along a longer corridor will pack more people into the room and a wider corridor with a bigger door will do it more quickly and the greater weight of people in a longer corridor will pack the room more tightly. But whatever to get maximum room packing, the trick is to close the door before any people spill back out.

There will be a balance between the size of the room, the door, the corridor and the right time to close the door for maximum effect.

It’s the same for the crankcase volume, port area, inlet tract length and inlet port closing time, there is a balance point.

It’s a bit of a simplification but to do it justice it would take a lot of thoughtful writing that I don’t have the time or skills for.

And there has been a lot written about this already on the net and in books, mostly 4-stroke but with a little imagination and thought it can all be applied logically to 2-strokes.

So its all out there, and I have posted links to what I can find, you just have to go looking……and reading.....and thinking for yourself........and if you are so inclined, you can post links to any good bits you find for others to enjoy too, like I do.

As you can see from the video, your friends look like they are wrong or just havn't got there yet.

Unless they can explain why, don't listen to "nay sayers", negatives are two a penny especialy on the net.

Getting a plenum to work is about understanding and applying basic principles.

As you see, it can be done......:niceone:....so good luck with your own plenum project.

That is quite interesting, there is a bit of information available that uses the " Schluß Vekauf" pricipal.

I can't remember who wrote it, but it points out that, in the case of air acting in such a situation, like you say, it just compresses into that smaller volume, like, (for example) a bunch of women going through a door on a handbag sale.....normally, they would go through a narrow door, one at a time, but, when there is a sale on (Schluß Verkauf), somehow, they manage to get 5 through at a time, with no ill effect.

I'm not being a "ney sayer" here Teezee, far from it, I am just showing interest in your work, and sure, I am questioning certain aspects (I never said you had fitted a Reed Valve), that is how development is done, is it not.

I am not just going to read things on the web, and simply follow them in blind faith (I doubt you would either).

I appreciate you writing the last post, and I am familure with what you have written, but I still don't understand how only a 3cm longer inlet tract can balance out the pressure that occurs when the inlet disc closes, and you have (I don't know......3 Bar?....that's just a number, it's likely less) in the plenum, and 1 bar on the other side of the carb, leaving a 2 bar difference between the carb mouth, and the disc face....that pressure, with no check valve between it, has to go somewhere, and since the blow off valve is seating, it only leaves for the carb mouth.

"springyness" of air not withstanding, that "spring" has to uncoil, and if the disc is closed, the only other options are the blowoff valve (no) or the open carb mouth.

You say that the only change you made was to increase the inlet manifold by 35mm, is this 100% correct?, you didn't change anything else?

I have indicated my interest in this project (as have a few others on here), and your description/pictures of your plenum is just getting vague.

If you don't want to continue with your description of this part of the project, for competition reasons, that is your choice, but like I said, this has been well hyped, and there will be some dissapointment!

None of this is intended as a personal attack Teezee, like I say, I am simply interested in the real world viability of such a system, and I cannot see how a 3cm increase in manifold length rectified such a big resonance problem.

I found this after one google search......

http://www.patentstorm.us/patents/pdfs/patent_id/5410999.html

you will have to join, but it doesn't cost.

[Buckets4Me]

You say that the only change you made was to increase the inlet manifold by 35mm, is this 100% correct?, you didn't change anything else?


I dont think that the problem was all that bad ( or as bad as you thought maby ?)

the bike was drivable around the track just a little off at times

it got better and worse with jet changes but was always able to get it around the track

as for Hype I think that going from 14 odd HP to 22 in a year of development for Taupo is not so bad (who els has done that Woody ??)
and then building a bike that is different from anything out there is also due some Hype
specialy when it feels faster than the other bike

if he says it's a sucess then you can safley say thats it got more HP than an old Gn125 Ha ha.
The next lot of development will be on the frame and suspention (and new enginesfor Chambers and Nedkelly)

come to the track and have a look for yourself (everyone els can and dose)

[SS90]

come to the track and have a look for yourself (everyone els can and dose)

Video and photo's is fine.......

[Kickaha]

Video and photo's is fine.......

What? you can't be arsed popping over for a look or something, lazy fucker :bleh:

[TZ350]

I'm not being a "ney sayer" here Teezee, far from it, I am just showing interest in your work, and sure, I am questioning certain aspects (I never said you had fitted a Reed Valve).

I appreciate you writing the last post, and I am familure with what you have written, but I still don't understand how only a 3cm longer inlet tract can balance out the pressure that occurs when the inlet disc closes

You say that the only change you made was to increase the inlet manifold by 35mm, is this 100% correct?, you didn't change anything else?

I have indicated my interest in this project (as have a few others on here), and your description/pictures of your plenum is just getting vague.



Hi SS thanks for the link. I will join and see what they have.

No you didn't say I used a reed valve, you said it wouldn't work without one, clearly it does.

And Yes I expected you would have a reasonable grasp of induction resonance and the difference between what happens at inlet opening as opposed to closing and why.

" is this 100% correct?, you didn't change anything else?"......what are you trying to say.

"your description/pictures of your plenum is just getting vague.".....My design objective and reasoning has been well covered, you now know it works, look at the picture below and short of sending you a set of blue prints, how much more do you need.

Want to know more, copy it and preform your own experiments.........and remember to tell people you saw it working here first.

The Magic Vacuum Cleaner 01 http://www.youtube.com/watch?v=YxiEo8cgopg

[SS90]

So where have you added the extra 35mm of inlet manifold length, is the the trumpet on the disc, or the box section between the inlet manifold rubber and the crankcase?

[TZ350]

So where have you added the extra 35mm of inlet manifold length, is the the trumpet on the disc, or the box section between the inlet manifold rubber and the crankcase?

the trumpet on the disc

[SS90]

I see, but that doesn't add to your inlet manifold length....we have discussed this at length (pun pun), and it is difficult to calculate the actual length of a two stroke inlet manifold as it is a "resonating flask",(because it includes the dynamic volume of the crankcase) as the air/fuel mixture is being heated and cooled at the same time by the surrounding metal, (and I think F5dave mentioned the oil as well) therefore we cannot calculate sonic speed, but, how does adding a bell mouth to the disc increase the inlet manifold length?

Is a plenum not calculated into the equation for inlet manifold length?

I have never seen a formula indicating that.

I'm not simply arguing, I am actually interested!

[SS90]

What? you can't be arsed popping over for a look or something, lazy fucker :bleh:
Ya miss me already?


I knew it!

Sorry I didn't get to say goodbye last month, I will try to bring you a pair of leather shorts next time.:niceone:

[TZ350]

.

You are confusing yourself with technoese.

1. The setup you see works.

2. I always tried to differentiate between the motors inlet tract and the carbs tract. maybe I should have called them 1 and 2.

3. Reversion happens at significant changes in diameter/volume, for instance where an inlet runner finishes inside a plenum.

4. A lot of 4-stroke stuff I read on the net treated the inlet runner, plenum and throttle bodies as separate entities in their calculations. These people clearly had a wealth of experience. I posted the links. You can chose to ignore them if you want to.

5. Calculation gets you into the ballpark, after that its test, test ,test........

[SS90]

.

You are confusing yourself with technoese.


No I'm not.

Putting aside the resonant flask portion of an inlet manifold, say, for one part of the equation, you wold measure the volume of the crankcase (at TDC), and you also need to add the inlet pipe length (among other easily calculated factors, cross sectional area of the inlet etc)

Any extra length that you added between the disc and atmosphere will not effect the over all length of the inlet tract.

Longer stroke crank, that would effect the length, (as it effects crankcase volume, as well as the length of the intake pipe) as would a spacer on the carb, but not because that effects crankcase volume, but rather that it simply adds length to the intake pipe length

[TZ350]

Putting aside the resonant flask portion of an inlet manifold, say, for one part of the equation, you wold measure the volume of the crankcase (at TDC), and you also need to add the inlet pipe length (among other easily calculated factors, cross sectional area of the inlet etc)

Any extra length that you added between the disc and atmosphere will not effect the over all length of the inlet tract.

Longer stroke crank, that would effect the length, (as it effects crankcase volume, as well as the length of the intake pipe) as would a spacer on the carb, but not because that effects crankcase volume, but rather that it simply adds length to the intake pipe length

This is where I have to stop you.

This thread is about sharing with other 2-stroke bucketracers ideas that might help in competing against the dreaded FXR’s and SS150’s. It’s about having fun and enjoying the company of the whole small bike racing community.

Although I have a working plenum chambered bike I am not here to be the design engineer for someone who makes their living tuning 2-strokes or to assist a commercial enterprise.

I have already posted every thing you need, including links, in fact I posted the key to all of this again just this morning. If you don’t understand it, trawl through the links I have posted and think through what you read there like I did.

Your becoming lost and confused, keep it simple and for Gods sake, get over yourself and read some net info, before “Telling Me” more about how things work.

I have a functioning plenum chamber and understand how it works…….you don’t......its that simple.

[SS90]

I'm not feeling the love here.

[Yow Ling]

So what are you going to do about that frame ?
I have just done some work on my forks following F5 Daves suggetions with some success.
22hp will be giving that GP frame universal joint a workout, would it fit in your RG50 frame, I can post a picture of an rg 50 frame with a kv100 if you like

[TZ350]

I can post a picture of an rg 50 frame with a kv100 if you like

Yes please, I would like to see that..

[Yow Ling]

Yes please, I would like to see that..

http://i975.photobucket.com/albums/ae234/YowLingRacing/yellowperil.jpg

There it is, turns out I cant post it , must be too stupid after all

[jasonu]

So what are you going to do about that frame ?
I have just done some work on my forks following F5 Daves suggetions with some success.
22hp will be giving that GP frame universal joint a workout, would it fit in your RG50 frame, I can post a picture of an rg 50 frame with a kv100 if you like

Mate, RG50 frame and 22hp. You're having a laugh.
The whole thing might be moot anyway. I have heard there is going to be a move to change the rules to allow 125 h20 2 strokes with no carb restrictions. If this is put to the MNZ, you, me, and all of the 150 coal burner crowd need to stand up and be heard.

[Kickaha]

I have heard there is going to be a move to change the rules to allow 125 h20 2 strokes with no carb restrictions. If this is put to the MNZ, you, me, and all of the 150 coal burner crowd need to stand up and be heard.

Chances are by the time we heard it would be to late, so how much does a RS125 Aprilla go for then?

Might have to see about about the capacity limit for 4 strokes getting upped to 200cc :lol:

[Yow Ling]

Mate, RG50 frame and 22hp. You're having a laugh.
The whole thing might be moot anyway. I have heard there is going to be a move to change the rules to allow 125 h20 2 strokes with no carb restrictions. If this is put to the MNZ, you, me, and all of the 150 coal burner crowd need to stand up and be heard.

It would still be better than a GP125 frame.
Is somebody or a group of somebodys pushing this change, I personally dont think its needed, but wouldnt be bothered if it happened. It would maybe cause the FXR brigade to be stronger with more FXR single model competitions to start up. What are the merits of 125 watercooled when a 100 will do the business ? Maybe start a new thread on this as it has nothing to do with TZ's development stuff

[jasonu]

It would still be better than a GP125 frame.
Is somebody or a group of somebodys pushing this change, I personally dont think its needed, but wouldnt be bothered if it happened. It would maybe cause the FXR brigade to be stronger with more FXR single model competitions to start up. What are the merits of 125 watercooled when a 100 will do the business ? Maybe start a new thread on this as it has nothing to do with TZ's development stuff

You are right, almost anything is better than a GP125 frame. No offense to the GP125 folks, the plain truth is that particular frame was never intended to cope with that much hp and the on track forces (cornering, brakeing) that type of hp will deliver.

The merits of a 125 vs 100 with the same rules is odvious, 25% more cc = more power. If it happens I will be looking for some RG500 barrels. I agree with you, it is not needed or wanted (by me anyway)
I think these points are valid in this thread as the machine being developed, described will most likely be uncompetitive if these rules are let in.

Right, I am off to watch the Indianapolis super cross. It is live on TV right now.
Vinaka

[TZ350]

I like the rules the way they are and I am enjoying finding new ways to live with the 24mm carb rule. It would be a pity to see the FXR's go their own way, I don't think old style buckets would last long on their own.

The GP frame is not great and bracing it hasn't helped us any. Two of the team have opted for RS chasis but Chambers and myself kinda want to do it the old school way.

We have examined every part of the frame and fork internals, fitted emulators and experimented with different spring rates and shocks, but don't know what the answer is yet.

When we are on top of the engine we will have a serious look at what we can do chasis wise and if we need to go to a doner bike....F5 Daves posts on forks and handling make very interesting reading.

[Buckets4Me]

I like the rules the way they are .

yes but hows an aprillia 125
with water cooling
and a 6 speed box sound
all fitted to my RS frame

:)
# Engine Type 122 - 22 kW (30 hp) (Successor to the 123 engine) I WANT THIS ONE !!!
# Engine Type 122 - 11 kW (15 hp) (same as the Type 122 22 kW engine, though restricted by removal of RAVE Power valve).

Max Speed 150 kmph (not at Mt Welly)
Max Power 33bhp (Hmmmmm YEA)
Seat Height 805 mm (ok)
Weight 121 kilos ( Shit I'd rather have an FXR) (thank goodnes for honda's)
0 - 100 kph 15 secs (not after changing the gearing)
Capacity 125 cc (124.5 cc dumbo. before the first second and third oversize)
Fuel Economy 40 mpg (yea right )

[ajturbo]

sorry, but it would still struggle against the might of the GT....

[Buckets4Me]

sorry, but it would still struggle against the might of the GT....

well that does it then
I'm not wasting the money if I cant beat the mighty GT :)