ESE's works engine tuner

[TZ350]

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170/88 ... Red Line on graph.

I recall someone talking about dyno testing a rotary valve two stroke. Where the valve seized in the fully open position at WOT and max RPM. With the sympathetic inlet resonance it apparently still made the same power but it did not pick up again once the throttle was closed. Probably explains how maximum powerwise I got away with crazy ass timing. Looks like more subdued timing is required if I want to ride the thing.

[husaberg]

.
170/88 ... Red Line on graph.

I recall someone talking about dyno testing a rotary valve two stroke. Where the valve seized in the fully open position at WOT and max RPM. With the sympathetic inlet resonance it apparently still made the same power but it did not pick up again once the throttle was closed. Probably explains how maximum powerwise I got away with crazy ass timing. Looks like more subdued timing is required if I want to ride the thing.

Pretty sure Frits or Jan wrote something similar to that about one doing that in practice or a race. ran good but refused to start again
Pretty sure piston ports get harder to start as the inlet duration gets extreme as well.

What would change if Rob contoured the leading edge and trailing of the disc to the same shape as the round ish port.
not meaning duration more so time area and intake pulse?

TBH I thought that port would be squarer.

[wobbly]

The RSW is a slightly oval inlet port horizontally, the RSA is slightly oval vertically on the disc axis.
The RSA is better in that the narrower the port for the same timings, the less time the disc covers the port shape.
Having rounded disc leading or trailing edges , with the same timings, does NOT make more power.
That was the first test I did at Zip when the 256 engine was introduced.
Having a slightly triangular port with straighter angled sides, is better than a round port, but always has bad wear issues, the RSA vertical oval is easily the best.
All dyno proven reality.

[koba]

Re the TF125 .pack info. I thought I would do a couple of pages at a time and suggest changes as needed.

Thank you, certainly appreciate the input!

The MSV with a 0.9 squish gap is way, way low. Changing the width back to 50% and going to 0.65mm gap gives 39M/s which is close to the recommended start point of 40M/s
for most applications.
With this very short stroke, that depth will be nowhere near the piston clipping in the overev.

Good to know, my target was around 0.6mm but I chickened out with the compression ratio getting so high. As it was I decided to file the piston down to reduce that, until I chickened out on the piston crown thickness.
The head had already been skimmed, that and the slugs for the crank balance were the only uses of machine tools in this project.
(The objective being minimal input to get to a good starting point).

The CCR - if you add the Transfer volume , found on the transfer page we get 566cc with those ducts added in. This equals a CCR of 1.278, is this what you actually measured as it is quite big
for a piston port , and well big for a reed engine.

I've probably stuffed that up, the transfer data was from measured sizes and the crankcase volume (including transfers) from a liquid measurement. (a holey piston). I'm pretty sure there were a number of 330ml liquid measurements being made that night too, so yeah, likely a cockup. I'll see if I can convince someone to check my working...

I automatically put the Exhaust Transducer at the duct length - to measure what the Mach is at that point later in the sim optimization, so I put in 72mm.

That's another oversight on my part, I noted your earlier advice on that and missed it here.

Moving onto the Exhaust Port.

The corner rads are OK, but the top and bottom timing edges are way too flat.
Using the FOS guidelines we get 4.5mm for the top corners and a center radius of 75% of bore = 42mm.
The bottom corner should extend up to around TPO , to reduce short circuiting, so I put in 10mm
This reduces the Blowdown STA, so I simply widened the port out to 40mm = 71%, so safe, and that got us back to the 24Hp Blowdown STA needed.

Awesome!

The duct exit is enormous, as the original 36mm = 127% of the port area, using the software radio button gives us a 30.4mm exit = 90%.
This should be easy to do by counterboring the duct and pushing in an insert, then grinding and blending the shape.

It's a bleeding whopper eh!
I do wonder about that as bikes of that design period all seem to approach it with this rapid increase in cross section, I do wonder if there was some rationale at the time or if it's just the way it ended up.

Either way, given project parameters the insert was not an option for this build. I did consider it, and also thought a smaller engine that is allowed water cooling, might even be able to get some cooling water in there.

However, if I ever do another one I will try following this, thanks!

So there is the first set of changes I recommend.

Thank you!

I was going to ask your opinion on which would be more worthwhile, between a better optimised head and a better optimised exhaust duct.
I'm still interested, but of course we are talking about an engine simulator, I can also model it and see!

I know the whole thing is a system and that optimising it all to work together is the best option but I'm also always interested in working out what step to take next, I guess this comes from me building bikes up that I am still racing each month, rather than building something up to a given spec from day one.

[koba]

I know the whole thing is a system and that optimising it all to work together is the best option but I'm also always interested in working out what step to take next, I guess this comes from me building bikes up that I am still racing each month, rather than building something up to a given spec from day one.

A quick run with the duct and head changes made...
(I haven't yet corrected the exhaust port window).

I'm guessing the minimal change from the head would be because combustion efficiency parameters are dealt with elsewhere.
I set it at 0.8 as a bit of a guess, I'll try another run with a higher number to gauge the effect of an increase here.

I also note I have it set to 95 octane where the engine actually runs on Av-gas.


Yep, from .80 to .85...



So, conclusion: both will be good, ideally do both at once!

I should also note, the model used with these graphs is straight line in the ignition, so there is power to be found above and below peak in setting that up well.
My way of approaching this has been to keep ignition timing as a relatively static variable for these calcs, (14 de BTDC).
Then I dial it in on the track, upping the advance under peak and tapering it off over peak, it makes a massive difference.
I've only done this with rudematary instrumentation (RPM and EGT), maybe oneday it would be good to get some knock stuff in there.
(Acually, one bike has the knock stuff thanks to F5dave)

[wobbly]

So running AvGas and a properly working squish, with a digital advance curve I will be putting in a CE of 0.9 and a com of 17:1 with such a low bmep and thus low dynamic compression.

[quallman1234]

TST100 Update - two stroke twin 100cc - 2x Derbi 50 cylinders...

https://www.youtube.com/watch?v=ZxXQ...l=GlenSkachill

[F5 Dave]

Nice one guys. Be on the track in no time.

[wobbly]

Next couple of pages for the TF125_WOB.
The transfers - this engine has no PV thus using the Aprilia reverse scavenging with the B - C highest will naturally kill front side.
Better to use normal stagger with the A highest as this regime naturally favors the generation of front side power, at the expense of course of overev.
But as we have a 50 stroke peaking at 11,000 I didnt consider overev was a driving necessity.
So without changing any axial or radial dimensions I have simply set the port heights to give close to the needed Transfer STA with normal stagger.

Then the Inlet/Reed page.
I changed the petal material to Carbon, then adjusted the 1st Mode thickness to give the correct rpm.
Then lifted the port roof and widened it a little to get the Inlet STA to match the Blowdown/ Transfer STA capability.

In the Exhaust page the duct exit is 36 , in the Pipe page it is 34, what is correct.

EDIT - at this point you dont need to choose between a duct mod or a head mod, as the head has no squish velocity and needs WAY more compression for AvGas.
Only issue is that if you do the insert trick later, then basically most of the pipe has to be changed to suit.

EDIT 2 - You dont need a knock gauge at all, the instant you get deto starting the EGT will flatline or drop if you are lean anywhere in the jetting with the advance you have.
Its good to have on the dyno to see how hard you can push the envelope without damage.

[koba]

Next couple of pages for the TF125_WOB.
The transfers - this engine has no PV thus using the Aprilia reverse scavenging with the B - C highest will naturally kill front side.
Better to use normal stagger with the A highest as this regime naturally favors the generation of front side power, at the expense of course of overev.
But as we have a 50 stroke peaking at 11,000 I didnt consider overev was a driving necessity.
So without changing any axial or radial dimensions I have simply set the port heights to give close to the needed Transfer STA with normal stagger.

Then the Inlet/Reed page.
I changed the petal material to Carbon, then adjusted the 1st Mode thickness to give the correct rpm.
Then lifted the port roof and widened it a little to get the Inlet STA to match the Blowdown/ Transfer STA capability.

In the Exhaust page the duct exit is 36 , in the Pipe page it is 34, what is correct.

EDIT - at this point you dont need to choose between a duct mod or a head mod, as the head has no squish velocity and needs WAY more compression for AvGas.
Only issue is that if you do the insert trick later, then basically most of the pipe has to be changed to suit.

EDIT 2 - You dont need a knock gauge at all, the instant you get deto starting the EGT will flatline or drop if you are lean anywhere in the jetting with the advance you have.
Its good to have on the dyno to see how hard you can push the envelope without damage.

Awesome.

36 is the correct figure for the exhaust duct exit. (and pipe entry).

[diesel pig]

.
I recall someone talking about dyno testing a rotary valve two stroke. Where the valve seized in the fully open position at WOT and max RPM. With the sympathetic inlet resonance it apparently still made the same power but it did not pick up again once the throttle was closed. Probably explains how maximum powerwise I got away with crazy ass timing. Looks like more subdued timing is required if I want to ride the thing.

It was this story that made me think that Frits 24/7 inlet would be worth looking into and after our Norwegian friend made a crude 24/7 inlet on his 50cc and run it on his dyno and worked it by just pulling a lever and it just worked intrigued me. but I will have to finish my case reed before mucking with a 24/7 inlet.

[diesel pig]

Just a follow up on my Ignitech questions I can get the coil pick up wires 250mm away from the ign coils all the way to the unit. Will I still need to run them into shielded cable? Because of the frame layout I will need to run the wires of the ignitech tachometer output and clutch control launch wires within a 100mm of the the ign coils will I need to shield them?

[pete376403]

Just a follow up on my Ignitech questions I can get the coil pick up wires 250mm away from the ign coils all the way to the unit. Will I still need to run them into shielded cable? Because of the frame layout I will need to run the wires of the ignitech tachometer output and clutch control launch wires within a 100mm of the the ign coils will I need to shield them?

You have a length of twisted pair shielded cable - why not try it?

[diesel pig]

You have a length of twisted pair shielded cable - why not try it?

I am one of those people that can do Auto wiring but loathe doing. If I can avoid even some of it I will but if the ones that know more than me say it must be done I will.

[wobbly]

Not needed as long as you have resistor plugs and caps.