ESE's works engine tuner

[Frits Overmars]

the short stroke means the only way to generate power is by holding up the torque at much higher rpm.
13,000 is nothing to a 50.7 stroker..

13,000 is nothing to a 50.7 stroker from a piston speed point of view. But the time.areas in a short-stroker are a different cup of single malt,
preventing you from holding up the torque even before you reach 13.000.

So Frits , you believe I am kicking a dead horse trying to make better power at 12500 with overev to 13,000 - thats about 1200 past the original.

The way I read it, and looking at the power curves you posted, I assumed that you wanted to make max. torque at 13000 rpm. And that would not have been a very healthy horse.

[Javier Ruda]

Hello wobbly, just an idea. When the fresh mixture must be pushed back in the cylinder it will find an exhaust port that is diminishing the height until it finally closes. Compared to a longer stroke engine the shape of that port could have a worse Cd on a short stroke engine because it will be not so “square”, needing an additional time to push back the mixture.

I think I was wrong. If the wave comes back earlier, it will be gone earlier too.

[wobbly]

Na Frits , I was shooting for peak power@12500 with overev to 13,000.
I simply could not get decent numbers @ 13000 , just as you said.
Even @ 12500 the STA predictions were maxed out at 43 Hp , and with a clever pipe and some serious fiddling in the sim that is what it made.
But it fought me every step of the way , detoing at the drop of a hat as everything was pushed so hard to get that theoretical ( but shit never the less ) result.
Makes it obvious now why the 4DP was a lemon for all those years in the 90's.

I know Rich Oliver won a bunch of USA titles with one - but even though the Yanks think so , that aint the Worlds by a long shot.
We have discovered an old guy who won some All Japan Cup races - he has a pair of super special Sugo 4DP cylinders sitting on a shelf in his shop.
Be interesting to see what was actually considered fast back then.
But the more I look into it - the 3XV TZR cylinder seems far superior in ultimate power capability.

[skako]

Hi Frits,
I have been customizing various exhaust pipes for the sims for a long time now. I try to compare most of those tubes that are published with the better ones.
All pipes are connected to the same test model in the sim (50cc).
They all have the same entrance and a total length of 825 mm. The output from the cylinder is a Wobbly (90%) concept.
The initial model I started with was the basic FOS-tube model.
I was looking for as much power and as wide a power band as possible, but so far none of the tubes have been better than these three (P1, P2, P3).
Frits, are you interested in this and could you come up with a better P4 tube on the default sim model. Pipe which would be above these three.

[husaberg]

Na Frits , I was shooting for peak power@12500 with overev to 13,000.
I simply could not get decent numbers @ 13000 , just as you said.
Even @ 12500 the STA predictions were maxed out at 43 Hp , and with a clever pipe and some serious fiddling in the sim that is what it made.
But it fought me every step of the way , detoing at the drop of a hat as everything was pushed so hard to get that theoretical ( but shit never the less ) result.
Makes it obvious now why the 4DP was a lemon for all those years in the 90's.

I know Rich Oliver won a bunch of USA titles with one - but even though the Yanks think so , that aint the Worlds by a long shot.
We have discovered an old guy who won some All Japan Cup races - he has a pair of super special Sugo 4DP cylinders sitting on a shelf in his shop.
Be interesting to see what was actually considered fast back then.
But the more I look into it - the 3XV TZR cylinder seems far superior in ultimate power capability.

Without going back through old stuff and i am open to correction, but i think there was a tie up with Bud Askland and Rich Oliver at time. Pretty sure Bud had also tuned Kokinski 250 tittle bike.
Is there room in the cases to stroke the engine to 54 ish.

[Frits Overmars]

Hi Frits,
I have been customizing various exhaust pipes for the sims for a long time now. I try to compare most of those tubes that are published with the better ones.
All pipes are connected to the same test model in the sim (50cc).
They all have the same entrance and a total length of 825 mm. The output from the cylinder is a Wobbly (90%) concept.
The initial model I started with was the basic FOS-tube model.
I was looking for as much power and as wide a power band as possible, but so far none of the tubes have been better than these three (P1, P2, P3).
Frits, are you interested in this and could you come up with a better P4 tube on the default sim model. Pipe which would be above these three.

Hi Skako, I appreciate the offer and I was curious enough to dive into it even though I don't really have time for it.
I don't have any data on your engine so I couldn't check your diameters and lengths; I could only look at the length percentages of your pipe segments and I found clear differences. The FOS percentages are 32-34-8-26 and your percentages are 34-34-8.4-23.6. Your end cone in particular is markedly shorter.

The maximum power of 10.2 kW or 13.9 hp in your graph requires a Ø 11,6 mm end restrictor diameter, but in your case it is Ø 13 mm, preventing the engine from building up pressure, exhaust gas temperature and revs. By the way, 13.9 hp is about 10 hp below the current 50cc top level.

Finally you write: "The output from the cylinder is a Wobbly (90%) concept". But as I have mentioned repeatedly, you must not mix the Wobbly concept into the FOS concept.

[Mike Fisher]

https://www.cycleworld.com/sport-rider/dominator/ - We Ride Rich Oliver's AMA Championship Winning Yamaha TZ250 - This motor hits hard, hits now and is tuned for a rider that values top-end steam over midrange drivability. Rich confessed, “My work goes toward top-end power. I spin my engines hard and that means I replace parts more often than most, but it's worth it to me. I've worked with some good tuners over the years and Bud Aksland has answered a lot of questions for me, helping me arrive at this particular combination." Oliver's right; most of the bikes in the AMA 250 field don't see 13,000 rpm all season and peak out between 12,300 and 12,700 rpm. Rich added, “If this was a national, I'd work on the jetting until it spun even higher.”

[philou]

The maximum power of 10.2 kW or 13.9 hp in your graph requires a Ø 11,6 mm end restrictor diameter,

13mm was dangerous, 11.6mm will still more be fun
​

[Frits Overmars]

13mm was dangerous, 11.6mm will still more be fun​

If it's dangerous, remove the danger; don't increase it.
But how is it dangerous? Too little cooling, too much ignition advance, compression ratio too high, squish gap too big? Bad fuel? All of the above?

[skako]

Hi Frits,
I'm glad I caught your attention. I am attaching a graph with your last recommendations, from which I started researching the best tube for my model. I know that it is not the maximum. That's why I check possible combinations before cutting the sheet and making the pipe itself. I need to perform certain operations on the cylinder, which are very limited for my capabilities.
If you can spare some time, I would appreciate your analysis.
I can send you these few pack-files for a quick check.
I apologize to everyone for some sentences that may not be well composed in the spirit of the English language because I use google translator to convey my thoughts.

[yatasaki]

Skako, are those pipes/curves for standard gearbox or it is new independent sim?

[skako]

Skako, are those pipes/curves for standard gearbox or it is new independent sim?

I need to transfer the characteristic of the pipe to my program and see it exactly (and this is done manually by typing, so it takes a long time). This way, at first, I can conclude that it can use a standard gearbox.

[Frits Overmars]

I am attaching a graph with your last recommendations, from which I started researching the best tube for my model.... If you can spare some time, I would appreciate your analysis. I can send you these few pack-files for a quick check.

Skako, the length percentages of the pipe segments are still the only data I can check with the info I have available, and these percentages are now in line with the FOS concept.
The initial diameter X is an important part of the concept and my first impression is that your 24,3 seems rather large but without knowing the exhaust timing, the cylinder capacity and the rpm of maximum power, this is just a gut feeling. But as I wrote yesterday, I don't really have time for it so I have to leave it at that.

[philou]

on a 50cc of 13 hp a stinger of 11.6 is equivalent to a stinger of 17 or 18 mm for a 125 cc of 30 hp.
it does not exist and the temperature will soar and burn the oil film

[Frits Overmars]

on a 50cc of 13 hp a stinger of 11.6 is equivalent to a stinger of 17 or 18 mm for a 125 cc of 30 hp.
it does not exist and the temperature will soar and burn the oil film

Philou, you may notice a couple of things in my exhaust concept.
1: The end restrictor diameter depends on crankshaft horsepower. The cylinder capacity does not play any role in the calculation of the restrictor diameter.
2: The stinger, as you call it, should have an internal diameter of >1,2 x the restrictor diameter. For 30 hp that stinger diameter should be >20,4.

I have no data of a 125cc engine that produces 30 hp, but I can provide you with data from a 125 cc engine that produces 54 hp at the secondary gearbox shaft, which corresponds to approximately 57 hp at the crankshaft. The restrictor diameter of that engine is 23.3 mm. Do the math if you wish.
That engine did not suffer from soaring temperatures and it did not burn the oil film. It did win a number of world titles....