ESE's works engine tuner

[Norman]

You're right, of course. And even on the Aprilia RSA, with all those goodies that you're not allowed to use on a kart engine, like electronic power valve, pulsed power jet and 3D-ignition timing, a less restrictive restrictor could have its use. That is one reason I designed the restrictor-bypass shown in the drawing below (the other reason was to avoid high-rpm part-throttle detonation). But Jan Thiel retired before it could be put to the test.
Attachment 339641

Thinking about this problem with high "rpm part-throttle detonation". Could it help if one would combine the above restrictor bypass with an ATAC and a Suzuki type tripple blade exhaust valve (for example) where the third, top blade, would be higher up than normal and used to only be opened together with the ATAC valve at high rpm part throttle situations? It would relief the cylinder pressure earlier and the ATAC would change resonance such that return wave will be delayed (weakened?) and the restrictor-bypass lowers the magnitude of any moving pulses?

[Norman]

Second blade..as the third blade is not moving, just for filling out the top.

[Frits Overmars]

Thinking about this problem with high "rpm part-throttle detonation". Could it help if one would combine the above restrictor bypass with an ATAC and a Suzuki type tripple blade exhaust valve (for example) where the third, top blade, would be higher up than normal and used to only be opened together with the ATAC valve at high rpm part throttle situations? It would relief the cylinder pressure earlier and the ATAC would change resonance such that return wave will be delayed (weakened?) and the restrictor-bypass lowers the magnitude of any moving pulses?

Yes, increasing the blowdown angle.area beyond its present value would help counteract the high-rpm, part-throttle detonation, Norman. Your third blade (the Aprilia cylinder already has two blades) would also clutter up the shape of the exhaust port timing edge, which would cost power everywhere, and it would interfere with the coolant access around the exhaust port.

[Norman]

Yes, increasing the blowdown angle.area beyond its present value would help counteract the high-rpm, part-throttle detonation, Norman. Your third blade (the Aprilia cylinder already has two blades) would also clutter up the shape of the exhaust port timing edge, which would cost power everywhere, and it would interfere with the coolant access around the exhaust port.

Yes Frits, you are right, the timing edge there will not be so good..

[Peter1962]

You're right, of course. And even on the Aprilia RSA, with all those goodies that you're not allowed to use on a kart engine, like electronic power valve, pulsed power jet and 3D-ignition timing, a less restrictive restrictor could have its use. That is one reason I designed the restrictor-bypass shown in the drawing below (the other reason was to avoid high-rpm part-throttle detonation). But Jan Thiel retired before it could be put to the test.
Attachment 339641

Frits, your concept of a variable tailpipe / restrictor-bypass was probably born with the idea to implement it on the absolute top performing two stroke engines at that time : the 125 cc GP engines and even the best at that : the RSA by Jan Thiel. What do you think of a possible use in other categories, like MX ? Do you think that your system could benefit a modern 250 2 stroke engine, of course when coupled with a well designed exhaust ?
The 250's are not that far behind a 450 foulstroke, but they suffer very badly from a less usable (more narrow) powerband compared to the newest 4 strokes.
Could your system be a way to broaden the powerband of an existing MX bike ?

[dutchpower]

Wel designed exhaust 262 cc 2 stroke ( were are the 450 fourstroke )

https://www.youtube.com/watch?v=38aIL9f_G7k

[Frits Overmars]

Frits, your concept of a variable tailpipe / restrictor-bypass was probably born with the idea to implement it on the absolute top performing two stroke engines at that time : the 125 cc GP engines and even the best at that : the RSA by Jan Thiel. What do you think of a possible use in other categories, like MX ? Do you think that your system could benefit a modern 250 2 stroke engine, of course when coupled with a well designed exhaust ?

For an engine without a power valve I would not hesitate to say yes, but I don't think we'll find a single MX-bike without a power valve these days.
The restrictor bypass will no doubt counteract high-rpm part-throttle deto on any engine, but those MX-bikes are not that highly strung: a 250 cc MX-engine makes less power than a 125 cc GP-roadracer, so maybe they haven't got that deto problem. You'd have to try it, Peter. And let us know what you find .

[TZ350]

Hello,
I just registered in this forum as I saw this very interesting topic. I'm glad to see someone is trying and sharing his ideas.
I built my own 2S EFI for my racing Solex (a very particular 50cc here in France).
The beginning is very encouraging, take a look : https://www.youtube.com/watch?v=LW19l64nm7Y.

I love it...... a fuel injected Solex racer.

[Muhr]

Sat at the computer a couple of nights ago and tried to make an excel sheet for an evaluation of transfertemp vs power that we are going to do in dyno. Do not think i got it right wondering if there's anyone who can correct below. Perhaps you who are injecting have knowledge about this
Added RSA values ​​as well as I know.
125 cc
Peake power rpm 13000
54hp crank
202 ° dur 56,767cc closed

Gas for this test
Octane (R + M) / 2 98
Research Octane 103
Motor Octane 93
Specific Gravity 0.762
Oxygen (weight%) 0
Leaded No.
BTU / Lb 18240
Btu / Gallon 115800 (cooling props)
Stoichiometric Air / Fuel Ratio 14.6

trapped volume121.4cc at 40 ° C mix and 40% Engine efficiency of trapped.!?

[Frits Overmars]

Try this Muhr.

Added RSA values ​​as well as I know.
125 cc
Peak power rpm 13000
54hp crank 54 hp at the gearbox exit shaft= about 57 hp at the crankshaft
202 ° dur 56,767cc closed 57,4 cc trapped stroke volume above the exhaust port + 8,6 cc combustion volume
Gas for this test
Octane (R + M) / 2 98
Research Octane 103
Motor Octane 93
Specific Gravity 0.762
Oxygen (weight%) 0
Leaded No.
BTU / Lb 18240
Btu / Gallon 115800 (cooling props)
Stoichiometric Air / Fuel Ratio 14.6 Lambda=0,85; actual air/fuel ratio=12,5
trapped volume121.4cc at 40 ° C mix and 40% Engine efficiency of trapped. Trapped volume=66 cc , 140% efficiency

[Muhr]

Try this Muhr.

Hello Frits thanks oracle

What I did was tried to calculate the minimum amount of air / fuel needed for each revolotion to be able to produce the desired power output with the energy content of this specific fuel.
So with your new values, I get 128,1cc trapped at 13000rpm or
1: 1,945 in pre-compression. which I do not believe.
Do you remember which fuel RSA run on?

[Frits Overmars]

Hello Frits thanks oracle
What I did was tried to calculate the minimum amount of air / fuel needed for each revolotion to be able to produce the desired power output with the energy content of this specific fuel.
So with your new values, I get 128,1cc trapped at 13000rpm or
1: 1,945 in pre-compression. which I do not believe.
Do you remember which fuel RSA run on?

The fuel was AGIP, 102 octane, with 5 % oil mixed in.
For me, trapped volume means the maximum volume above the piston when all ports are closed. But obviously you use a different definition. What's yours?

[Muhr]

The fuel was AGIP, 102 octane, with 5 % oil mixed in.
For me, trapped volume means the maximum volume above the piston when all ports are closed. But obviously you use a different definition. What's yours?

As the calculation is now, I need 128.1cc of air at atmospheric pressure doing work to produce 57hp crank.
I agree with your definition of trapped, I was unclear

[Matt@TYGA]

For an engine without a power valve I would not hesitate to say yes, but I don't think we'll find a single MX-bike without a power valve these days.
The restrictor bypass will no doubt counteract high-rpm part-throttle deto on any engine, but those MX-bikes are not that highly strung: a 250 cc MX-engine makes less power than a 125 cc GP-roadracer, so maybe they haven't got that deto problem. You'd have to try it, Peter. And let us know what you find .

So maybe a redesign of the pipe biased towards the top rpm range, with a smaller restrictor, and then the bypass system to reduce the chance of deto (if this now becomes an issue), and also bring the midrange back up. Just a thought.

[husaberg]

So maybe a redesign of the pipe biased towards the top rpm range, with a smaller restrictor, and then the bypass system to reduce the chance of deto (if this now becomes an issue), and also bring the midrange back up. Just a thought.

Matt could you give us a run through on how to tell NSR model cylinders apart and what the differences are?