ESE's works engine tuner

[porttiming124]

I sent my cylinders this week to have the nichasil removed, I will receive them within 10 days.
During this time I am looking at the STA in engmod to find the duration of the transfers.
I see that with the optimized transfer width I can have less duration and even more

here are the STAs with the wider and lower transfer.
I worked on the height of the transfer to match the achievable power of the BLW (which I do not touch)
It seems to me to make sense but what do you think of low duration like that?

[nitro2tfx]

Nitro , why do you say the exact same functionality is a stretch ? I can use the sim output data to super accurately predict the performance of every single change to an input element.
Be it a 1mm change in header length , to 1* change in ignition timing.
And to boot it has outputs for every concievable performance indicator , that you would need another 20 sensors to log.
The x axis scaling I mentioned simply due to you commenting that pipe design analysis was a point of interest .
In this regard all we need to see happens between EPO and EPC ie centered on BDC , what the pipe/port pressure ratio is doing when its closed is pretty much irrelevant - thus stretching this scale gives much better insight.

I have microscopic data for the TZ350 LSR engine as it was completely designed in EngMod . Starting with a 250G cylinder and a 58mm Banshee crank the pipe , ignition , squish , compression ,reed thickness ,intake length ,duct areas/mach , everything was optimized with probably a Kg of alloy Tig rod.
And its a testament to Neels code that every single element was built as designed on screen , it went to the salt having only been started from cold , did a few runs to get the Lectrons dialled in -
then smashed the LSR record out of the park.
Have a look on Jeff Henise FB page , all the mods done are there in detail - https://www.facebook.com/jhenise/pos...55500252306228

Where to start. There are lots of performance predicting simulation software programs, some 2 stroke, some 4 stroke, likely some rotary ones exist as well. Most of them predict performance of a build and/or guide the build fairly well, some better than others. I think everyone knows that, or should.

There are some big differences between predicting performance/guiding a build with simulation software versus actually measuring pressure waves.

1) Measuring pressure waves allows you to actually see the pressure waves as they are (within sensor positioning limits). Simulation software does not have to get the waves exactly right to make people happy, it just needs to get the performance prediction close to make people happy. Measured pressure waves and combustion pressures show what happened, even for transient events that only happened on one cycle or a handful of cycles. Lots of interesting things to see cycle to cycle.

2) Measuring pressure waves (and combustion pressures) allows you to do things inside the box, a little outside the box, and also WAY WAY outside of the box, no limitations. Since it is recorded data you know just what happened inside the engine, for every single cycle for the whole test whether on a dyno, or at the track. No ifs, ands, or buts about it, every cycle, not averaging of events. What happened in the engine, as recorded, is what happened in the engine, it is not dependent on software limitations, nor wishful thinking, nor what SHOULD have happened in the engine, it is a factual recording of what actually happened. Lots to be learned when you see everything that happened, not just an average.

3) Ignoring what happens with the pressure waves when the exhaust port is shut is a mistake. True when one uses simulation software it doesn't matter because there is nothing you can do about it, the output is the output and depends on the input. However, when the person behind the keyboard is doing the thinking, instead of the software, that changes the picture entirely, what happens with the port shut is valuable info, that's why we display it in our graphs.

4) Lots of fast vehicles have been built without using either measured pressures or simulation software pressures, the two technologies are bonuses for sure, both separately and together, but they are not the only way to skin a cat. Just depends on who is doing the cat skinning lol. To be honest something fast designed without pressure measuring equipment or simulation software is a more impressive feat.

5) The companies that make pressure sensors have been around for several decades, it is a multi millionaire dollar industry and continues to grow. Pressure sensors are NOT inexpensive, if simulation software was functionally exactly the same, no one would be manufacturing the pressure sensors nor buying them.

6) When one relies SOLELY on simulation software, one is automatically locking themselves in to being "no better than the rest". Anyone using the same simulation software can build something equally as good. This is not true of using recorded pressures, recorded pressures pits one person against the next, ingenuity vs ingenuity, the end products will not be the same. Simulation software gives a person a leg up on those that don't have it, or aren't adept at using it, but simulation software in conjunction with pressure recording equipment gives a person two legs up.


I'm not trashing Neels software in any way, it is very good software, but it is not correct to think that simulation software is the exact same thing as recorded pressures, it isn't. There are benefits to simulation software and there are benefits to recorded pressures, that's why having both together is the cat's meow.

[Vannik]

Where to start. There are lots of performance predicting simulation software programs, some 2 stroke, some 4 stroke, likely some rotary ones exist as well. Most of them predict performance of a build and/or guide the build fairly well, some better than others. I think everyone knows that, or should.

There are some big differences between predicting performance/guiding a build with simulation software versus actually measuring pressure waves.

3) Ignoring what happens with the pressure waves when the exhaust port is shut is a mistake. True when one uses simulation software it doesn't matter because there is nothing you can do about it, the output is the output and depends on the input. However, when the person behind the keyboard is doing the thinking, instead of the software, that changes the picture entirely, what happens with the port shut is valuable info, that's why we display it in our graphs.

Nitro, very good response as per usual.

Ignoring the effect of the closed cycle is not something the sims do though. Attached a pdf I distribute with my software.

[andreas]

I haven't been on here in a long time, what's the trick to getting a jpg to show directly in a post (not as an attached thumbnail).

I have the jpgs loaded on Dropbox but adding the Dropbox links to the post doesn't seem to do anything according to the preview.

Thanks.

Anyway the thumbnails show high speed RECORDED pressure data (cylinder, intake, exhaust) that I promised ages and ages ago. I planned to have crankcase pressure too but will have to do that another time. Yamaha Banshee with some mods, details to follow.

I don't understand, how can the returning wave be 70% larger than than the outgoing?

[nitro2tfx]

I don't understand, how can the returning wave be 70% larger than than the outgoing?

There are more waves in that pipe (or any pipe) than just the blowdown wave and the returning negative and positive waves. Always. Waves add up and the result at any point in time (or angle) is the summation of the waves, some generated from the current cycle, some generated from the previous cycle.

The pressure waves in a particular pipe for any particular cycle are dependent on the pipe/porting of course, they are also dependent on the combustion process in the cylinder for that cycle, ..........AND the pressure waves that are still ringing back and forth from the previous cycle (or cycles). That's why it is important to know what happened in the previous cycle as well as the cycle of interest.

Another thing that most people don't realize is that in a spark ignition engine the combustion process varies quite a bit from one cycle to the next, so the driving force for the pipe varies from cycle to cycle. A modern diesel engine is a different story, the combustion cycle is just about the same cycle after cycle after cycle, for a given rpm/load, but in a spark ignition engine it is not like that, every cycle is different from the one before it and after it.

[nitro2tfx]

Some first order results of comparing a Banshee sim with measured traces. Some comments:

1. The sim model is currently a very rough approximation of the real engine and even more so with the pipe, I have no idea what the Toomey T6 looks like.
2. The porting is mostly based on the RZ350 model, until somebody supplies better.
3. I digitized the traces Nitro posted and then used a small amount of smoothing, getting csv files will be better.
4. For some reason I had to shift the inlet trace by 45 degrees to get alignment between the sim and measurement.

When I have a chance I will see if the T6 pipe dimensions happen to exist somewhere online.

As for the intake, where was the "sensor" placed in the simulation software ? Was any sort of bellmouth etc. used on the carb in the software ?

[TZ350]

IAnyway the thumbnails show high speed RECORDED pressure data (cylinder, intake, exhaust) that I promised ages and ages ago.

I planned to have crankcase pressure too but will have to do that another time. Yamaha Banshee with some mods, details to follow.

I would be very interested in the crankcase pressure data.
.

[Muhr]

Don't be disappointed if you test a carb with improved CFD and don't see a corresponding increase in output on the dyno.

After my own carb experiments I concluded that the inlet was most likely not the restriction that is holding the engine back. I found most of my improvement by improving the "Transfer" and "Trapping" efficiency of the motor. Rotary valve, big crankcase volume, A ports angled higher than the B ports.

I spent a lot of time playing with improving carburetors as their size was class limited for me. The thinking was that a 24mm carb would restrict a 125cc two stroke to something less than 20 RWHP. On the dyno, after a lot of development I made as much as 32 RWHP with a 24mm carb and single exhaust port.

But I found my air cooled motor could not reject enough waste heat to make 32 RWHP sustainable on the track. 28 RWHP was sustainable and 22 was very reliable. Heat rejection issues probably explains why the factory 125cc air cooled road racers of the day were about 28HP.

Nice work. It is not easy to get that type of power out of an air-cooled engine with single exhaust

I hope I have ok setup in terms of transfer, exhaust, crankcase volume etc. Where I see as the biggest challenge for me is to get enough time area for the intake as I want to get peak hp closer to 22m / s which I think will be very difficult.
In a previous project that I helped a friend with, that was the biggest challenge. It was a 50cc cvt (Rotary valve)that we took out max at 15500.
Miserable to start and stuck below 3000, if you happened to drop it below 8000.

Prof Blairs take on a Bellmouth.
https://www.yumpu.com/en/document/re...air-associates

That was the article that made me start thinking about it. I was looking for something completely different when I stumbled across it. then it was a simulation that eventually became many.

[wobbly]

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.

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.
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.

Sure I agree lots of fast engines have been designed without any data , be it from a sim or live.
Perfect example though would be the last homologated TM kart engine. The pipe design for that took 4 people 4 months full time to build 25 pipes, dyno test the result and then try to decide what did or didnt work.
I did over 100 sims , built 3 test pipes , dyno and track tested them , plus produced a new CAD file of a way superior Exhaust duct , all in 3 months , alone.
The result was a huge advance in power - in exactly the places asked for , on the dyno and on the track.

Absolutely impossible to achieve , without using a good code that deleted the need to build and verify a huge number of multiple design theories.
My opinion now is that there is very little " cleverness " in doing that task without data , just a huge wasted amount of expense and time , with no way of guaranteeing that there was not alot " left on the table "
apart from a pile of useless pipes.

But the end game here is , if your results from comparing an apples for apples sim against live data ends up improving Neels code , in any way ,shape ,or form , im really glad for your help.
Just dont presume all we are doing is being " happy " by looking at the very last part of the equation for build sucess = a power graph.

[Muhr]

Anyway, I'm thinking of reworking a carburetor to get this tested.

Had some time to spare today so now it's done.

[philou]

Muhr, Maybe this could inspire you

https://www.motomeccanicaracing.it/2...7/kit-phbg-21/

[OopsClunkThud]

Here's the "master template" that I made from info in the Blair paper as well as the curtain length that wobbly published. I may (or may not) have got it completely wrong.

link to parametric Fusion360 sketch.

I make a copy and size it to fit any given application.


https://a360.co/3pmDAZY

[SwePatrick]

Hi everyone has spent the Christmas weekend trying to understand what benefits different shapes of bellmouth have at different air speeds. Is it something that someone has investigated and if so, what have you come up with?
Have come so far that I can see an improvement in cfd but feel skeptical that I will see any major improvement in dyno.
Anyway, I'm thinking of reworking a carburetor to get this tested.

This design below has worked best for me:
On a mikuni vm42 taperbored from 43.5 to 48mm then radius tangent to the velocitystack.

[F5 Dave]

Muhr, Maybe this could inspire you

https://www.motomeccanicaracing.it/2...7/kit-phbg-21/

Inspires me to cut a Dellorto in 1/2

[JanBros]

Wob, have you experiented with "your exhaust duct" and it's influence on where in the rev-range it benefit's ?

need to make new exhausts for my KR1 as I'm building one with an RGV swing arm and because of it's wider knuckle in the rear suspension, the (very good) original pipes no longer fit.
I do not want any more HP because the cylinders can not handle al lot more than standard, they crack at the rear mounting holes because the base is to thin.

So I'm wondering if you have advise on a duct that benefit's power lower down the rev-range ?