ESE's works engine tuner

[Frits Overmars]

Frits, wondering if you would be willing to comment further on the RSA125. My question at present is in the downsweep of the exhaust duct. I believe you are at roughly a 30 deg downsweep from center of exh port to center of the exh duct outlet. Was there any testing on varying this angle flatter or steeper? How important do you view this angle? I have a significant library of cyl specs from all different forms of two stroke applications, and it seems to run the gammit. I have some hunches but cant really prove or disprove any of them with my available resources. Does this angle affect the looping direction of the transfers? It would seem to me a flatter angle would obviously give a better time area, but would also tend to "bend" the charge from the transfers in a short circuiting manner quicker. Or maybe you view the roof of the exh port as more important? Any experiences or thoughts?
Myron

I am willing allright, Myron; I am trying to promote two-stroke knowledge. But I'm short of time as it is.
Regarding testing: if you can think of anything at all, you can be sure it was tested.
Maybe the picture below will answer some of your questions. There is a lot more where this came from and I am willing to share, but you would have to convince your forum governor to allow uploading ZIP-files.

[teriks]

The yellow trace is the pressure at the exhaust port.

Wob am I reading this right?

Attachment 250838

On the left the pipe is sucking the cylinder down to late for the transfer port opening TPO.

And on the right the exhaust pulse is arriving back to early, before the transfer port has properly closed TPC.

Now this will be interesting.. testing my knowledge.

"On the left": Id say you need to increase exhaust blowdown, not fiddle with the pipe. If anything the lowest pressure in "Pexport" should occur later, around BDC.
"On the right": I agree.
As it is simulated, the pipe seems tuned for max power at higher rpm than simulated, but you may lack blowdown time*area to run such rpm's.

[dmcca]

Re the ignition problems at starting.
Two things, firstly reverse the wires from the trigger and delete the reverse polarity button in software.Many times the trigger wired backwards gives very odd results when strobed.
Secondly, look at the "number of programmings" no way have you done 33,000 changes - this means the ECU is being corrupted by RF noise, you need to check the resistor plug cap and plug, as well as
ensure that the hot wire to the coil is well away from the trigger wires etc.
Also the curve is very odd.
Any tuned engine will like 28* advance in the mid under the pipe, then where the bmep starts to rise as the pipe works, around 8000 in your engine, you start pulling out timing, heading for around 15* at peak torque.
Depending upon how its set up, then less advance may be needed at peak power and beyond to make it rev out.
Below is a curve for similar rpm as your example.

Thanks for this info

I did the things you suggested and spent a couple of hours re-routing wiring and checking all connections, etc... and... it wont start at all now with the ignitech, even when reinstating the previous settings... however i discovered the following...

- with the plug out while cranking the kickstarter by hand the ignitech gets a single spark very occasionally, not enough to start though, regardless of polarity of the trigger. This must be what has been happening to produce hard starting.
- with a 12v battery connected to the system it sparks every revolution, even with very slow turning of the flywheel, regardless of polarity of the trigger.
- the stock ECU still works fine, sparks every revolution without a battery and always starts extremely easily.

Seems like the ignitech is not getting the power it needs at startup and therefore is sparking intermittently causing difficult starting. Does the ignitech have a higher power requirement at startup than a stock ECU?? Otherwise it looks like a bad stator or elec system.

With the "number of programmings" from brand new it read around 32,000?!?!? I found this a little strange.

With the ignition curve i will adjust it accordingly. Going by some sim results peak torque should be around 7500-8000 and max overrev about 9500... thats where ive set the limiter anyway.

[Myron]

I am willing allright, Myron; I am trying to promote two-stroke knowledge. But I'm short of time as it is.
Regarding testing: if you can think of anything at all, you can be sure it was tested.
Maybe the picture below will answer some of your questions. There is a lot more where this came from and I am willing to share, but you would have to convince your forum governor to allow uploading ZIP-files.

So.... I take it you tried flatter and steeper angles on exh duct than whats in the pic? What were you learning?

[Frits Overmars]

So.... I take it you tried flatter and steeper angles on exh duct than whats in the pic? What were you learning?

I didn't; Jan Thiel did. And we learned that the result in the pic is the best. I also learned that you won't stop asking questions .
I don't mind; I would do the same if I were you. But answering them would require more time than I have available right now. There's an engine design waiting.....

[TZ350]

http://www.trademe.co.nz/Browse/List...x?id=424848013

A copy of MOTA 6.10 2-Stroke engine development software.

Sold this software sold through the buynow option within an hour of going on Trademe.

[speedpro]

Seems like the ignitech is not getting the power it needs at startup and therefore is sparking intermittently causing difficult starting. Does the ignitech have a higher power requirement at startup than a stock ECU?? Otherwise it looks like a bad stator or elec system.

I have a MB100 powered bucket with an Ignitech CDI. I'm running a Honda CRF250F, I think, generator and reg/rec and power capacitor. It starts in a couple of steps. With the plug out and in gear with it on the stand just pulling the rear wheel will cause a spark. From that I think the Ignitech starts operating pretty quickly once supplied power.

[quallman1234]

http://www.trademe.co.nz/Browse/List...x?id=424848013

A copy of MOTA 6.10 2-Stroke engine development software.

Yoink, thank you very much.

[wobbly]

If the stator has trouble supplying enough power, quickly enough,you can increase the "turns before firing" to say 5 or 10.
This gives the system a chance to ramp up, before the ECU starts to fire sparks.

Re your sim printout TeeZee.
Lots to be seen there.
Starting at the top, you are about 500 rpm below peak power in the sim at 11500.
The whole engine isnt very efficient as the D.Ratio is low for the rpm being close to peak.
The TexAv is very high ,over 600
The TuMax is low.
With the depression in the cylinder starting early, then dropping away, the pipe shape is wrong for that rpm.
The pipe is too short for that rpm, as the return pulse has dropped away before the piston is close to closing.
The port timing and the pipe length are not working together, you have no superposition on the far left.
Look at this 40 odd crank Hp RGV100 just over peak, read all the numbers,and note the pressure wave shape, this is as good as it gets.

Edit - you can see the effects of low blowdown, if you get a big jump in Transfer pressure ratio when they open.

[TZ350]

I am willing ... but you would have to convince your forum governor to allow uploading ZIP-files.

The mods are looking into it and also asking, how big are the zip files? apparently there is a limit.

[TZ350]

Hi Wob

D.Ratio
TexAv
TuMax
PexPort

there are lots of these abreviated names, I can guess at a few like D.Ratio for delivery ratio but most are a mystery to me, is there a list of definitions/explinations some place?

[wobbly]

yes DR is delivery ratio.
TexAv = average temp in middle of the pipe.
TuMax = max temp of unburnt gas in the squish.
PexPort = pressure ratio at the exhaust port.

Go into help from the Post 2T screen,then plot options, then performance traces, also go to thermo traces for those terms.

[F5 Dave]

Hmm, well I think I've had answered most of my questions on prev page by finally finding the time to trawl through the pitlane thread (oops how did it get to be tomorrow?). But haven't seen any crank pics of RSA, just curious.

[Myron]

I didn't; Jan Thiel did. And we learned that the result in the pic is the best. I also learned that you won't stop asking questions .
I don't mind; I would do the same if I were you. But answering them would require more time than I have available right now. There's an engine design waiting.....

Fair enough. That is the second time Ive pushed for your thoughts on this. Thanks anyway for your response and willingness to share.
Myron

[husaberg]

I know the real answer is to get a programmable ignition

But how do you produce/record a map a plain analogue ignition. I guess you mark the rotor and use a strobe and possibly a camera and a tacho but how do you do it say on a KTM 50 where the rotor drives the water pump and is inner rotor.

There must be an easier way? I have had a look on the net for a map of one and for how to do them but no joy so far.