ESE's works engine tuner

[wobbly]

JanBros , the duct rule of thumb naturally exhibits the trend of pumping up peak , and more so overev power.
This is soley due to the increased Mach in the duct ie approaching 0.8M if done correctly.
But due to this phenomenon it is then possible to redesign the pipe , such that it counters the trend of the duct by increasing considerably the mid and off pipe power.
Add the two together , and the result is a ton of midrange power , with no loss or gain in peak and overev than you had previously.

[Muhr]

I may (or may not) have got it completely wrong.


Attachment 348180
https://a360.co/3pmDAZY

I think you seem to have got it pretty right!

[dutchpower]

Big diff. in rpm

[SwePatrick]

I think you seem to have got it pretty right!

That huge radius on the bell would work better in a 4stroke setup.
Look at old gp bikes carburetors instead and simulate their setup.
As stated before, you might not look at max flow,,,,

[Frits Overmars]

That huge radius on the bell would work better in a 4stroke setup.
Look at old gp bikes carburetors instead and simulate their setup.

Here is that very same carburettor, fitted on an Aprilia RSW125, with its big black bellmouth. So looking at old gp bikes carburetors is indeed a good idea .

[Muhr]

That huge radius on the bell would work better in a 4stroke setup.
Look at old gp bikes carburetors instead and simulate their setup.
As stated before, you might not look at max flow,,,,

Hi Patrik I have simply made it so big that size is no longer a factor. It is my intention to use this for testing extremes in both directions. The easiest thing would have been to put on a larger carburetor. My hopes for something spectacular with this are low, what do you say knowledge is power. Have not gotten as far as you so I know what works for what and what flow speeds suit what.

[SwePatrick]

Hi Patrik I have simply made it so big that size is no longer a factor. It is my intention to use this for testing extremes in both directions. The easiest thing would have been to put on a larger carburetor. My hopes for something spectacular with this are low, what do you say knowledge is power. Have not gotten as far as you so I know what works for what and what flow speeds suit what.

I´d say with a huge radius the length of carb is becoming way to long.
I'm not 100% sure about this but a carb can almost never be to short in a highrevving engine, and by that one would never want to make it longer

And that´s what i´ve noticed in my dyno also, every time i made inlet length shorter it was a gain.

[nitro2tfx]

Nitro , plenty to agree with in your reply , but plenty to passionately disagree with as well.

You are making a huge assumption ( often just an error waiting to be revealed ) that everyone using a good sim is " happy " simply inputing data , then looking solely at the result in an output power graph.
That couldnt be further from the truth - the on screen wave form , as interpreted by the user " thinking " as you put it , reveals exactly what needs to be done next.
In this respect its just as powerfull as your interpretation of the real time wave forms using intellect/experience , but just using a different source of data.

I agree that simply looking at power output predictions may not be enough to make you happy, but it no doubt makes a lot of people happy. The people like yourself that are doing a lot of thinking about traces, and so on, are ASSUMING that in addition to the power predictions the simulated exhaust traces and intake/crankcase traces are right. The fact that power predictions are close to the real world in no way means that the exhaust traces are just as close, not at all. Obviously they are not horribly wrong, but by the same token they are not fantastically right and some details are lost. That is where some things are left on the table, currently.

You say ignoring the trace info outside of EPO - EPC is a mistake and anyway " nothing can be done about it " - so what can you " do about it " using the live data , nothing as well - except interpret the results.

I was saying that ignoring EPC-EPO is a mistake, makes no difference whether we are talking about simulation data or recorded data. That's why we plot it and the previous cycle. Neels indicated that the simulation software does not ignore EPC-EPO irregardless of whether the end user does or not. It does matter (see below).

If the pipe is well designed the result will always be 1 - as much superposition at EPO as possible , 2 - as deep/wide as possible depression around BDC , 3 - the highest peak return wave just before EPC.
Sure , we can interpret what is happening with legacy cycle waves combining or destructive interference , but what happens when the port is closed , ends up only affecting one thing , the relative strength of the
remnant pressure at EPO - nothing else.
It can go above and below a pressure ratio of 1 several times when the port is closed , but the only thing that actually matters is the end game, the strength of superposition.

"1 - as much superposition at EPO as possible" . Yes but the superposition needs to be close but not quite aligned and shape matters.
"2 - as deep/wide as possible depression around BDC" . Coarsely but shape of the depression matters somewhat too.
"3 - the highest peak return wave just before EPC" . Shape matters a lot and a higher peak with the wrong shape will not make more uumph.

4 - what happens EPC-EPO affects more than just the remnant pressure at EPO it affects the shape of the superposition pressure in the vicinity of EPO AND what happens during the depression around BDC

5 - traces with numerous unwanted oscillations, are well....unwanted, these unwanted oscillations can be due to the pipe design or due to minor fabrication imperfections, it doesn't take much, this can also be seen and eliminated using recorded data. Everybody has had a pipe that should have worked fine but didn't quite live up to expectations, sometimes this is nothing more than due to not so obvious minor details that set up additional oscillations. The recorded data shows if you have what you think you have, or you don't.

Wave shape, angular location and magnitude, all 3 matter.

[wobbly]

Dutch - from your plots I can see that at 21,000 the tuned length is spot on and in resonance with the port frequency.
You have exellent superposition that produced a huge amplitude wave down the diffuser , and a good return , correctly timed pulse just before EPC.
But the diffuser shape ( % Lt starting and or angles ) is all wrong - in that at lower rpm its doing almost nothing around BDC , and at the correct rpm for resonance , the max depression is far too late in the cycle.
This lateness of depression peak then , above resonance rpm , is even further off the scale to the right.

[Muhr]

I´d say with a huge radius the length of carb is becoming way to long.
I'm not 100% sure about this but a carb can almost never be to short in a highrevving engine, and by that one would never want to make it longer

And that´s what i´ve noticed in my dyno also, every time i made inlet length shorter it was a gain.

I understand that you have thought through the physics behind that.
With the BMEP numbers you present, I understood that you had solved it..... Luckily I have a few more variants to test.
Actually stood tonight and thought about how I could shorten the intake I understand that I have a bit left until I reach an acceptable level.
How do you usually do?

[ken seeber]

To me it is clear that predictive software and/or taking real time measurements are just some of the tools to assist in the design of one important functional component of the final product, in this case a high performance 2 stroke engine.

The real test is ultimately to use these tools in addition to skills, knowledge, imagination, experience, instinct and dedication to come up with an improved product each time.

[TZ350]

I'm not 100% sure about this but a carb can almost never be to short in a highrevving engine, and by that one would never want to make it longer And that´s what i´ve noticed in my dyno also, every time i made inlet length shorter it was a gain.

We went to an extreme with a short carb/inlet tract.

Pic-04 the new 33mm bellmouth feeding directly to the motor.

The idea worked Ok and made very good power but with the short inlet tract there was a severe resonance dip just before it came on the pipe. So severe that it would spit fuel past the front axle.



Increasing the length of the inlet tract greatly reduced the resonance dip.

It ran Ok.







If I could have solved the problem of fuel/oil dropout in the plenum I would use this idea. As it made very good low end power out of the corners and still had very good top end as well. On track tests it was a two stroke that drove like a bigger four stroke.

The plenum resonance seemed to plump up the bottom end remarkably. And if we could have automatically altered the plenum resonance (volume) I am sure we could have greatly improved the engine performance everywhere.

[wobbly]

The other consideration with inlet length is that the reflected wave off atmosphere is a gradual reversal of that waves sign.
End correction for the wave not reflecting off a hard medium takes care of this effect in a sim , but my take on large bells is that making them longer and much larger in diameter
may not in reality change the true reflection point , but it just moves the bell further into the reflection zone , improving the energy recovery of the area change.

[SwePatrick]

I understand that you have thought through the physics behind that.
With the BMEP numbers you present, I understood that you had solved it..... Luckily I have a few more variants to test.
Actually stood tonight and thought about how I could shorten the intake I understand that I have a bit left until I reach an acceptable level.
How do you usually do?

No calculations here
A lot of dynopulls tells the reality.

I often shorten the rear of the carb and make an intakeplate like modern cartengines have.
The carb protrudes into a plate bolted on the reed.



And below a cart engine, look at the carb, not a big radius in the bell, a taper into the throttle blade that begins with a small radius and a 'plane' that connects outward against where you mount the airfilter.




Ignore picture below,, something got messed up when uploading

[wobbly]

The KZ Dellorto kart carb is nothing special at all , its just what was homologated many years ago and no mods are allowed.
But one airbox manufacturer was clever and achieved what im sure all good tuners would have eventually come up with.
They made the rubber clamp on manifold effectively a continuation of the bell , with minimal extra length.
This is worth several Hp past peak over others that simply have an extension to the flat clamp surface.