ESE's works engine tuner

[Wos]

Wos, you may well be right, 15 degrees may be too much and I look forward to playing with the curve on a dyno at some point.
In the mean time that is not my main problem. I have to sort out what these pipes are up to. Last pipes had a large joiner between the mid sections, these do not. I dont remember this issue with the old pipes. These new pipes certainly make more top end power with more accurate press tool sections.

Old pipe ...new pipe...dosent matter...you are collecting experience...can do conclusions for next needs ...

In combination of changing ignition you can even get more insight whats going on... worth doing it before thinking about other pipe...


Mid section? Cilindrical part? Belly?

Do you work with fos pipe calculation?
Very good start and easy with jan bros excel

Belly diameter now...lengt from piston to end cone?

If i had to deal with your twin x

Would calculation do with 50 cc ...go with small diameter/ shallow pipe ...resonance length 8500...9000 wide powerband for enduro use...

If i am completely wrong...dear other better speacialists here...tell me...tell us!! top!

Grüße from enduro fellow

[Flettner]

So, what HP should we expect from an air cooled AG100 (125).
What is a sensible top end rev range for a 48 x 58 bore and stroke engine?
Wos, each pipe is loosely based on a KX65
Each outlet port nozzeled at approx 80% of port area, @ transfer just cracking open.

[Frits Overmars]

Resonance starts at 7500....Exhaust 195, transfer 130....Bore and stroke an unfortunate 48 x 58.

Unfortunate? It would be worse the other way around. Now you've got a 105cc engine with decent angle.areas, sufficient for max.power at >11000 rpm. With bore and stroke 58 x 48 you'd have a 127cc engine with angle.areas limiting max.power rpm to perhaps 9000.
Summary: the long-stroke engine would be able to produce the same power, albeit at higher revs, but with less thermal load on the piston.
You could of course force the short-stroker to produce its max.power at higher revs with a shorter pipe , but BMEP would suffer and max.power would not be any better.
I think there is a simpler way of designing a pipe than basing it on a KTM 65SX. With your above values, a cylinder capacity equal to 50% of your 105 cc and an estimated exhaust duct length of 70 mm it would look like this.

[Wos]

Did a Addition of the partial lengths firits showed us

859 mm pipe are about a peak resonance at 11000 rpm ...

If we calculate pipe with half engine capacity and half of its Horse power...volume of each pipe sinking to 50 percent too...a chance to get pipe temperature in ballpark ...I think

Hard to answer how much power ...

Stock 125 enduro or crosser bikes in early /mid 1980ties aircooled had max 28 hp...every horse more was a lie

[aljaxon]

hi chaps not posted on here for a while, been too busy making crap pipes. i'd like some pointers on a making a pipe for my 82cc aircooled motor 190/128, 50mm x 39.7mm (not by design) single ex port 6 transfers, crankcase reed intake. single gear variated. not a lot to go on i know but the power characteristics are the clutch bites at 9500 and the revs slowly rise to 9750 while the motor variates and then reaches full variation at around 10000 and then i would like it to reach max spead at 11500. i need zero over rev and nothing below the clutch bite point . so quite a narrow power band compared to pipes ive previously built. i could possible live with it revving to 11750.
i still havent forked out for engmod 2t yet due mainly to me not confident enough that i can input all the data accurately enough to give output of any value.
im making 3 pipes.
i.m wondering whether to aim peak power for max revs with a cliff after that or if thats a hard/impossible pipe to make + instead aim for smack bang in the middle of my rev range 9500 - 11500 ie 10500.
before i fitted this new clutch the motor would struggle to rev past 7000rpm. but now it doesnt have to operate at those revs and it flies

i know this is a how long is a piece of string question but id appreciate any pointers re percentages. its going to be around 750mm tuned length or slightly longer depending on what peak i aim for. start diameter 27mm.

[Condyn]

You just need to roll cones and try things. The following are things that I have found to work. It takes many attempts of dyno and field testing to get it nailed down
For a cvt pipe and the characteristics you are after, just make a simple 2 stage diffuser pipe to START with. You will likely not end that way. 30-31 percent header and keep your first diffuser shallow and long around 7 degrees. 2nd diffuser 15 or so degrees. 68 percent to end of diffuser. Take the total length of the diffuser and make 2/3 of it the first diffuser. Make your baffle cone around 25 degrees. If the power comes on too late make the first diffuser shorter and second longer so it opens to the 15 degree cone sooner.

[Wos]

Dear my teachers

Never did a pipe for cvt...but this leads me to interesting questions ��

Is Single endcone/baffle best for highest output at small powerband spread?
Then it should fit on cvt...

25 degree looks to me not verry steep...but somewhere i read from a limit...

Which angle of baffle is biggest effective number if small spread and max power is goal

Are there other numbers the limit depends on?

Thanks to all!!

Wolfgang

[wobbly]

The rear cone angle is interdependent upon two factors - the relationship between front side and peak/overev power , plus the belly diameter.
A 25* cone on a 100 diameter belly could be considered steep , but on a 140 Diameter pipe , well over 30* is getting " steep ".
The steeper the cone the less front side and overev is available , but peak is shifted upward - effectively narrowing the powerband.

I have been experimenting with two and three angle reverse taper rear cones.
These sacrifice a small amount of front side for a large increase in peak and overev power.
For a CVT, using this concept you would then lengthen the pipe , to bolster the power between peak torque and peak power, making it faster to hit the CVT lockup - by sacrificing the unnecessary overev.

[aljaxon]

You just need to roll cones and try things. The following are things that I have found to work. It takes many attempts of dyno and field testing to get it nailed down
For a cvt pipe and the characteristics you are after, just make a simple 2 stage diffuser pipe to START with. You will likely not end that way. 30-31 percent header and keep your first diffuser shallow and long around 7 degrees. 2nd diffuser 15 or so degrees. 68 percent to end of diffuser. Take the total length of the diffuser and make 2/3 of it the first diffuser. Make your baffle cone around 25 degrees. If the power comes on too late make the first diffuser shorter and second longer so it opens to the 15 degree cone sooner.

thanks condyn, i havent got enough time left on this planet to get it exactly nailed on. im an old git. i have a pal with a dyno but for my purposes it either works or it doesnt. i will gear to top speed and the fastest pipe wins.
those angles and proportions are almost exactly what i was told by wobbly would produce a good frontside pipe with no over rev. except the baffle cone was only 20 degrees. to get the baffle cone at 25 degrees i would need a long belly section.

i would have thought a longer belly does narrow the power band. but i know it doesnt always work out how you expect.

[aljaxon]

The rear cone angle is interdependent upon two factors - the relationship between front side and peak/overev power , plus the belly diameter.
A 25* cone on a 100 diameter belly could be considered steep , but on a 140 Diameter pipe , well over 30* is getting " steep ".
The steeper the cone the less front side and overev is available , but peak is shifted upward - effectively narrowing the powerband.

I have been experimenting with two and three angle reverse taper rear cones.
These sacrifice a small amount of front side for a large increase in peak and overev power.
For a CVT, using this concept you would then lengthen the pipe , to bolster the power between peak torque and peak power, making it faster to hit the CVT lockup - by sacrificing the unnecessary overev.

cheers wobbly, reverse taper as in going from from belly - sharpest cone - less sharp cone - even less sharp?

[wobbly]

Correct.
Here is an example for a Classic Roadrace bike

[husaberg]

Unfortunate? It would be worse the other way around. Now you've got a 105cc engine with decent angle.areas, sufficient for max.power at >11000 rpm. With bore and stroke 58 x 48 you'd have a 127cc engine with angle.areas limiting max.power rpm to perhaps 9000.
Summary: the long-stroke engine would be able to produce the same power, albeit at higher revs, but with less thermal load on the piston.
You could of course force the short-stroker to produce its max.power at higher revs with a shorter pipe , but BMEP would suffer and max.power would not be any better.
I think there is a simpler way of designing a pipe than basing it on a KTM 65SX. With your above values, a cylinder capacity equal to 50% of your 105 cc and an estimated exhaust duct length of 70 mm it would look like this.

I think he is in the worse off position I fear Fletter transposed his bore and stroke.
I muse he has a 58x48mm bore and stroke.
Those AGS are short of cylinder stroke as std and pretty sure he put in a bigger pin as well.
They start of as 52x45.6 similar engine to DT100 MX100
They are really a scaled up 80cc.

[Flettner]

Unfortunate? It would be worse the other way around. Now you've got a 105cc engine with decent angle.areas, sufficient for max.power at >11000 rpm. With bore and stroke 58 x 48 you'd have a 127cc engine with angle.areas limiting max.power rpm to perhaps 9000.
Summary: the long-stroke engine would be able to produce the same power, albeit at higher revs, but with less thermal load on the piston.
You could of course force the short-stroker to produce its max.power at higher revs with a shorter pipe , but BMEP would suffer and max.power would not be any better.
I think there is a simpler way of designing a pipe than basing it on a KTM 65SX. With your above values, a cylinder capacity equal to 50% of your 105 cc and an estimated exhaust duct length of 70 mm it would look like this.

It is 58 bore x 48 stroke.

[Betaversio]

Hello, question mainly for Frits and Jan,

I had a conversation with pipe-minded friend. We discussed how did you decide between two different power curves before a race, given specific gear ratios, weather conditions, and track characteristics. We were thinking how you did this when working at Aprilia team.

When designing something for a motor—perhaps in a simulator—you often have to decide what to build. Or when testing on a dyno and comparing 30 different power curves that look quite similar to the eye (one with peak power, another with better range), how did you choose between them?

I am familiar with your power range-concept. Instead of that, my friend suggested pipe design based on gear ratios and least missed area under ideal acceleration curve (what would be if motor is always at peak power). However, this approach doesn’t account for human factors, such as the need for mid-range and over-rev. While it’s possible to include these considerations, the result becomes a bit of a hocus-pocus calculation.

When simulating, I once started writing code to simulate a driver’s path around a track. I made drag racing version of it. I stopped working on track version because factors like varying pipe temperatures after corners and use of over-rev would have made the motor simulation inaccurate. This does seem to be only option, if it would be possible to make both track and motor simulation accurate enough.

Another possible shortcut is to optimize the engine using log data. For example, if the engine spends 4% of its time at 12,000–12,200 rpm and 5% at 12,600–12,800 rpm, these rpm ranges can be weighted accordingly to guide improvements. For me, this is most promising one, according to what is possible in normal tuner's resources. But, then there is problem that even when when we have two equal designs in this concept's, and power in different places in curve, pipes are not equally fast on track.

At least this is interesting...

If you others also have some thoughts, feel free to share.

Kind regards,
Antti

[Wos]

The rear cone angle is interdependent upon two factors - the relationship between front side and peak/overev power , plus the belly diameter.
A 25* cone on a 100 diameter belly could be considered steep , but on a 140 Diameter pipe , well over 30* is getting " steep ".
The steeper the cone the less front side and overev is available , but peak is shifted upward - effectively narrowing the powerband.

I have been experimenting with two and three angle reverse taper rear cones.
These sacrifice a small amount of front side for a large increase in peak and overev power.
For a CVT, using this concept you would then lengthen the pipe , to bolster the power between peak torque and peak power, making it faster to hit the CVT lockup - by sacrificing the unnecessary overev.

Thanks wobbly

Reverse 3 cone concept sounds to me as a combination of two worlds...for frontside keeping long resonance pipe length...and at powerpeak main actor is first very steep cone of baffle...gaining strong reflection there?

Does my picture fit?

Thank you very much!!!

Wolfgang