ESE's works engine tuner

[lohring]

[QUOTE=41juergen;1131069196]

No, I tried expensive
Lotus engine simulation
and Ricardo Wave
Results too far of what we measure.

Probably cause our engines have very different of "moto" geometry and exhaust.
So I afraid Engmod will not give us some useful guidance. We are going to prepare full scale CFD
calculation from intake to exhaust.

May be anyone can share Engmod user manual or complete tutorial?
I hate ask for evaluation and be regularly advertized.

Don't worry, Neels is nice guy engineer... :-) he is more in technology rather than asking people to buy his (very good!) software...

I've been an Engmod user for a long time. It's based on Gordon Blair's work on engine simulation that duplicates the resonant nature of a two stroke. It does not replicate scavenging or combustion like CFD but uses empirical models. If you understand the details of the engines you are trying to model, it's great for getting the resonant parts like the intake tract, reed valves, and pipes right. It has great graphs to help with understanding what's going on. It has been continually improved with inputs from some very experienced two stroke builders, several that post here. Neels is always ready to help, the help files are great, and my updates have been free for years. See http://vannik.co.za/EngMod2T.htm for the details.

Lohring Miller

[jbiplane]

I don't even fancy stepped pistons, let alone use foul-stroke practices to keep them alive.

Other idea a bit similar to ancient DKW
https://ac.els-cdn.com/S187661021400...66615a1f664ffa

[nitro2tfx]

The nice thing about a low compression ratio is not only that the peak pressure remains decent, but also that this pressure does not drop so much during expansion.
So even with an unaltered peak pressure there will be a much higher average pressure pushing the piston down. You gotta love nitro, don't you?
Well, maybe not always...

Yes, and on a 2 stroke both the lower CR and the nitro also put more energy into the exhaust, so it's win-win or maybe win-win-win, at least up until the point where you lose parts and start to shed tears

[RomeuPT]

Yes, and on a 2 stroke both the lower CR and the nitro also put more energy into the exhaust, so it's win-win or maybe win-win-win, at least up until the point where you lose parts and start to shed tears

which % can you use nitro on unleaded fuel without kill the engine right away? does it really make a dif?

Is there any product you can buy to mix with gasoline? Small percentages can really change jetting behavior?

[nitro2tfx]

which % can you use nitro on unleaded fuel without kill the engine right away? does it really make a dif?

Is there any product you can buy to mix with gasoline? Small percentages can really change jetting behavior?

0 % unless you are really good at your chemistry.

Nitro doesn't blend directly with gas, it just sinks to the bottom because it is far more dense than gas. Nitromethane is used with methanol applications.

Nitropropane will blend with gas, but nitropropane is hard on the engine and gives not very much of a power increase compared to nitromethane. You probably would get more power just switching from gas to methanol than you would by adding nitropropane to gas, and the power on methanol would be reliable.

[breezy]

Same operating conrod-free engine

https://www.youtube.com/watch?v=dwwvidC8CWo

In second video, he said that bigger engine 1600cc 45kg 200hp.

https://www.youtube.com/watch?v=_fuR3HLz-0A

Its very very precise and too much moving parts

https://www.youtube.com/watch?v=LboS59_0j1w

some great videos you have found there katinas.... led me onto the joseph newman electric motor videos ... which i found very interesting although off topic.

[lodgernz]

...A 14,75 mm end cone restriction should be good for over 22 crankshaft-HP, so no problem there.

Frits: I'm using your formula for end cone restrictor Dtailrestrictor = 3.06*SQRT(HP).

My 50 produces 11.8HP at the wheel, optimistically 13 at the crank, so this tail restrictor diameter calculates as 11.0mm.

When I made my pipe, I just couldn't believe such a small outlet was viable, so I made de Laval nozzles of 14.0, 14.25, 14.5 and 14.75.
On the dyno, we started with three pulls on the 14.0, then 3 pulls on each of the others. In every case, the power went up as the nozzle size went up.
I didn't have any bigger nozzles to try, so the last set of pulls was with no nozzle, just the 19mm ID tailpipe. The power dropped markedly.
The 11.8HP reading (at 13,000RPM) was with the 14.75.

Have I got the formula for end cone restrictor right? If so, is 11mm really safe on a 50?

[Frits Overmars]

You've got a couple of things right, starting with the crankshaft power.
As a rule of thumb I assume a power loss of 2,5% per transmission step (this is not carved in stone; CVT transmissions and bevel gears will properly mess things up).
So 97,5% of the crankshaft power arrives at the gearbox input shaft (if the oil level in the transmission and the oil viscosity are not too high).
97,5% of 97,5% exits at the output shaft (if: see above).
97,5% of 97,5% of 97,5% arrives at the wheel via the chain (if the chain and sprockets are well lubricated and not worn).
97,5% of 97,5% of 97,5% of 97,5% arrives via the tire at the dyno drum (if the tire pressure is not too low).
So the total efficiency from crankshaft to dyno is 0,975^4 = 0,904.

You quote 11,8 HP at the wheel, but I take the liberty of assuming that it was not measured at the wheel, but on a dyno drum driven by the wheel. Then the crankshaft power will have been 11,8 / 0,904 = 13,06 HP , so your estimate is realistic and your 11 mm restrictor should be about right.

The restrictor factor of 3,06 that you quoted, stems from an older version of my FOS exhaust concept; you'll find the latest version below. that factor has now grown to 3,1 but that won't make a world of difference; 13,06 crankshaft-HP would now require a Ø 11,2 mm restrictor.

Is that safe on a 50 cc engine?

That depends. The engine has to be thermally sound. A cylinder with a pressed-in liner is not great in this respect, and neither is aircooling. And watercooling is OK only if you have sufficient circulation of not-too-hot water.
You'll also need sufficient blowdown time.area, otherwise hot combustion gases will enter the transfer ducts and heat up the cylinder. So don't rev it too high.

The above thermal requirements apply to tuned engines. 13 crank-HP out of 50 cc should not give big problems, but you must be aware of a possible interaction.
Your power was measured with a Ø 14,75 mm restrictor. If you were to try the 'correct' 11 mm size, power might go up and 11 mm would not be correct any more...

Finally, a smaller restrictor will increase mean pipe pressure. If the blowdown time.area is insufficient, this increased pressure will enhance the problem of exhaust gases entering the transfer ducts.
A smaller restrictor will also increase the exhaust gas temperature, and hence the resonance frequency of the exhaust pipe. If the pipe was too short already, switching from too big a restrictor to a 'correct' restrictor size will cause a loss of power and power band.

That's two-strokes for you: they seem simple .

[RomeuPT]

Frits: I'm using your formula for end cone restrictor Dtailrestrictor = 3.06*SQRT(HP).

My 50 produces 11.8HP at the wheel, optimistically 13 at the crank, so this tail restrictor diameter calculates as 11.0mm.

When I made my pipe, I just couldn't believe such a small outlet was viable, so I made de Laval nozzles of 14.0, 14.25, 14.5 and 14.75.
On the dyno, we started with three pulls on the 14.0, then 3 pulls on each of the others. In every case, the power went up as the nozzle size went up.
I didn't have any bigger nozzles to try, so the last set of pulls was with no nozzle, just the 19mm ID tailpipe. The power dropped markedly.
The 11.8HP reading (at 13,000RPM) was with the 14.75.

Have I got the formula for end cone restrictor right? If so, is 11mm really safe on a 50?

That is a good test. I follow some experience I have and things I have read here for the pipes I do. I do the restrictor depending on the expected horse power and the tail pipe diameter along 0.5 to 2mm bigger depending on what is available, I also have found that having less then 10cm of stinguer hurts power in many cases. But those are not real state of the art tests or anything just some experience. I also give less restriction for aircooled or poeple wanting broad power.

I would say optimal restrictor to expected HP:

12-15hp - 14 to 16
15-20hp - 16 to 18
20-25hp - 18 to 20
25-30hp - 19.5 to 22 (125 road bikes)

and so on

[Juho_]

If running the engine on alcohol fuel (like E85, methanol..), shouldn't the tail pipe diameter be larger? Am I correct?

My new pipe has a 16mm ID tail pipe, but the engine is supposed to rev +16,000rpm.
Peak hp is around 14,000rpm depending on jetting, deck height.. and so on. Was 'designed' for 13,000rpm peak hp (700mm length).
Probably on E98 fuel it'll produce its peak hp at ~13,000rpm, going to test it some day because of cold temperature (less than 0*C)

Previous pipe had a 19mm ID tail pipe and peak hp @ ~13,000rpm and produced higher peak torque and hp numbers.
Currently the engine is having problems with producing power... something is restricting it and power has went every time to the 'wrong direction'.
Sometimes I didn't need to do any changes and the power had already dropped -- probably some of this is caused by loose fit on clutch side ball bearing on crankshaft.. and cylinder itself is restricting it to rev any further or producing more power. Sadly my 90 degree mini grinder (modified ebay dentist grinder) broke, again, and cannot do anything for it..

Of course, the pipe itself might be worse than the previous one.
I had an idea to get the engine rev higher with the new pipe and find more hp by doing modifications on the cylinder (mostly).
20hp at real dyno (the numbers posted are gsf dyno numbers, not comparable) and 16,500-17,000 max. rpm is my goal currently.
Probably it won't be achieved on this engine because of its many problems (gearbox and clutch do not really like the 16,000rpm revs when doing full throttle pulls through all 6 gears...)

[RomeuPT]

If running the engine on alcohol fuel (like E85, methanol..), shouldn't the tail pipe diameter be larger? Am I correct?

My new pipe has a 16mm ID tail pipe, but the engine is supposed to rev +16,000rpm.
Peak hp is around 14,000rpm depending on jetting, deck height.. and so on. Was 'designed' for 13,000rpm peak hp (700mm length).
Probably on E98 fuel it'll produce its peak hp at ~13,000rpm, going to test it some day because of cold temperature (less than 0*C)

Previous pipe had a 19mm ID tail pipe and peak hp @ ~13,000rpm and produced higher peak torque and hp numbers.
Currently the engine is having problems with producing power... something is restricting it and power has went every time to the 'wrong direction'.
Sometimes I didn't need to do any changes and the power had already dropped -- probably some of this is caused by loose fit on clutch side ball bearing on crankshaft.. and cylinder itself is restricting it to rev any further or producing more power. Sadly my 90 degree mini grinder (modified ebay dentist grinder) broke, again, and cannot do anything for it..

Of course, the pipe itself might be worse than the previous one.
I had an idea to get the engine rev higher with the new pipe and find more hp by doing modifications on the cylinder (mostly).
20hp at real dyno (the numbers posted are gsf dyno numbers, not comparable) and 16,500-17,000 max. rpm is my goal currently.
Probably it won't be achieved on this engine because of its many problems (gearbox and clutch do not really like the 16,000rpm revs when doing full throttle pulls through all 6 gears...)

If you have a 1000rpm disparity from your calculations you may have failed the temp prediction from far, your ignition may need more retard at 13000, you may got wrong on the lenght/port height dimensions maybe both or all things combined

[Frits Overmars]

If running the engine on alcohol fuel (like E85, methanol..), shouldn't the tail pipe diameter be larger? ... Previous pipe had a 19mm ID tail pipe and peak hp @ ~13,000rpm and produced higher peak torque and hp numbers.... 16,500-17,000 max. rpm is my goal currently.... Probably it won't be achieved on this engine because of its many problems (gearbox and clutch do not really like the 16,000rpm revs when doing full throttle pulls through all 6 gears...)

If the engine does not behave stable, you can never be sure whether a modification is positive or negative, so I think that should be the first point to address.
When you are talking about tailpipe diameter, do you mean the restrictor diameter? These are two distinctly different things! The restrictor diameter depends on the engine power, not on the kind of fuel. The tailpipe diameter should be markedly bigger than the restrictor diameter, as shown in the above exhaust concept.

There are very few cylinders that have sufficient angle.areas for your current goal of 16,500 - 17.000 max. rpm.
Your remark that your previous pipe had a peak hp @ ~13,000rpm and produced higher peak torque and hp numbers, may be an indication that the angle.areas are already too small for max. power at 14.000 rpm. In that case, raising the rpm with a new pipe will lead to less power instead of more.

[Juho_]

If you have a 1000rpm disparity from your calculations you may have failed the temp prediction from far, your ignition may need more retard at 13000, you may got wrong on the lenght/port height dimensions maybe both or all things combined

On E98 fuel the peak hp is at ~13,000rpm (quick test).

When I did testing on the previous pipe, the peak hp was at ~12,000rpm on E98 fuel.
Switched to E85, and the peak hp rpm raised nearly 1,000rpm and engine revved further when re-adjusted the carburetor.

Current problems on the engine haven't existed very long, and I've done quite a lot testing with the new pipe.
With programmable cdi unit I did not get much more peak hp or revs, like I had thought because the old cdi unit's ignition curve was quite stupid for this engine. That's when I accepted the cylinder (39.90mm D50B0 with single ring piston, and 44mm stroke with 94mm conrod - Minarelli AM6 engine) was restricting it to revving more and producing more power , but unfortunately my 90 degree mini grinder broke as said on previous post so couldn't try it out.
This engine is going to be replaced as soon as I can get new tools to modify the new engine's cylinder.. larger cylinder bolt pattern, and reed valve case..and way better gearbox and clutch. But overall it isn't much different engine than the current one.

When you are talking about tailpipe diameter, do you mean the restrictor diameter?

Yes, sorry, I meant the restrictor diameter.

[lodgernz]

You've got a couple of things right, starting with the crankshaft power.
As a rule of thumb I assume a power loss of 2,5% per transmission step (this is not carved in stone; CVT transmissions and bevel gears will properly mess things up).
So 97,5% of the crankshaft power arrives at the gearbox input shaft (if the oil level in the transmission and the oil viscosity are not too high).
97,5% of 97,5% exits at the output shaft (if: see above).
97,5% of 97,5% of 97,5% arrives at the wheel via the chain (if the chain and sprockets are well lubricated and not worn).
97,5% of 97,5% of 97,5% of 97,5% arrives via the tire at the dyno drum (if the tire pressure is not too low).
So the total efficiency from crankshaft to dyno is 0,975^4 = 0,904.

You quote 11,8 HP at the wheel, but I take the liberty of assuming that it was not measured at the wheel, but on a dyno drum driven by the wheel. Then the crankshaft power will have been 11,8 / 0,904 = 13,06 HP , so your estimate is realistic and your 11 mm restrictor should be about right.

The restrictor factor of 3,06 that you quoted, stems from an older version of my FOS exhaust concept; you'll find the latest version below. that factor has now grown to 3,1 but that won't make a world of difference; 13,06 crankshaft-HP would now require a Ø 11,2 mm restrictor.

Is that safe on a 50 cc engine?

That depends. The engine has to be thermally sound. A cylinder with a pressed-in liner is not great in this respect, and neither is aircooling. And watercooling is OK only if you have sufficient circulation of not-too-hot water.
You'll also need sufficient blowdown time.area, otherwise hot combustion gases will enter the transfer ducts and heat up the cylinder. So don't rev it too high.

The above thermal requirements apply to tuned engines. 13 crank-HP out of 50 cc should not give big problems, but you must be aware of a possible interaction.
Your power was measured with a Ø 14,75 mm restrictor. If you were to try the 'correct' 11 mm size, power might go up and 11 mm would not be correct any more...

Finally, a smaller restrictor will increase mean pipe pressure. If the blowdown time.area is insufficient, this increased pressure will enhance the problem of exhaust gases entering the transfer ducts.
A smaller restrictor will also increase the exhaust gas temperature, and hence the resonance frequency of the exhaust pipe. If the pipe was too short already, switching from too big a restrictor to a 'correct' restrictor size will cause a loss of power and power band.

That's two-strokes for you: they seem simple .

Thank you Frits, very good information, as always. My engine is an NSR50, so is limited in blowdown time.area with a single oval exhaust port. It's water cooled of course, and happily over-revs to 14000 for short periods without exceeding water temp of 65º during a race. However, as you suggest, because I'm using such a big restrictor, the gas temperature and pipe pressure will both be low and this is borne out by the pipe length Lmax being only 678mm for an ex duration of 192º.
Lots of work to be done.

One more question, if I may: Your formula for Lmax features the constant 88, whereas I would have expected 83.3.
Is your constant adjusted for the fact/likelihood that the mean reflection point from the baffle cone is not at the pointy end of it?

[Frits Overmars]

Your formula for Lmax features the constant 88, whereas I would have expected 83.3.
Is your constant adjusted for the fact/likelihood that the mean reflection point from the baffle cone is not at the pointy end of it?

I did not want to badger aspriant-tuners with the whereabouts of a reflection point; the 88 is just a factor that ought to work good together with an assumed speed of sound of 550 m/s. That speed of sound itself is the value that can be varied by the concept's users according to their findings.