ESE's works engine tuner

[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.

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[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.

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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.

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[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.

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[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.

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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

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[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........so what do the legals think?.......cheat..or.......ok