ESE's works engine tuner

[JanBros]

Whats the crush you ran on the domes to make them seal properly

what do you mean by crush ?

all sealing is done by viton O-rings

[Greg85]

If you look at the STA numbers of an Aprilia cylinder it appears that the transfers are way ahead of the Exhaust as far as power making capability.
But if you look at the reality of the Exhaust Cd, with its huge radius on the top edge, that effectively begins to open above 200* duration with the port
roof itself down at 196* then it becomes clear that all the work done by hand in the R&D dept to match the Blowdown flow numbers with the transfers
gave a highly synergistic scenario.
Raising the transfers lost power - as did lowering them.
And the scavenging pattern along with the timings had been optimized quite early on.
The same with the Aux ports - any higher or wider lost power.
All dimensions being tested on the dyno and the best results kept in production - a slow to achieve, but highly accurate method for gaining GP winning power.

Thank you for your explanation wobbly, thanks frits for pictures fos scavenging, ok now I know there is no miracle a lot of research has to do in this area and as said frits it will take me more than 1 winter hahaha ...

[wax]

what do you mean by crush ?

all sealing is done by viton O-rings

I know how it's sealed we run those style heads all the time on Jetskis. But you have to have a certain amount of crush on them other wise the domes spin when you are removing or fitting the spark plugs

[seattle smitty]

I was wondering about that, too (I machined my own head for a 250cc Konig outboard back in the Pleistocene Era, but was too dumb to think of anything like inserts). If I were to do another, I would think that the insert should stand a little proud (like maybe .002"/0.05mm ??) of the outer housing's mating surface . . . which of course would depend on if it goes on over a gasket (and then how much does the gasket crush?). I didn't know the sled guys were already doing this. I can and would make the outer part (need some terminology here!!) hell-for-stout to minimize flexing, but would still suppose that the insert ought to protrude just a little.

I have looked at your 8-page link, JanBros, but if this info was there, I missed it.

[wobbly]

Yes, if you have inserted domes you need to have the outer flange sitting proud of the cover by around 0.03 to 0.05mm.
If they are made flush they eventually start to fret and then bounce up and down.
Unless of course the hold down bolts go thru the domes flange,but even in this case TM have the domes sitting up,and use a big O ring around the
outer water jacket with a shallow groove giving plenty of crush depth.
In any scenario the outer cover should be used to provide clamping force on the area around the plug threads - Jan told me of a situation where a new insert design
made alot less power, and he tracked it down to the combustion chamber flexing upward,reducing the com.
In the head shown, the small flat area outside the plug body within the chamber needs to be wider, or it will overheat.
Show us a section across the head so I can see if water is getting close enough to the plug threads.

[wax]

Ok here it is, i understand what your saying about the water cooling on the plug up in the cooling jacket area
your also telling me to make the area around the plug a larger diameter.
I can see there is no way that there is getting enough cooling.
I have the sides of the combustion chamber alot more vertical than in your instance, is this an issue ?
I think im going to owe you a bottle of muesli or what ever grain your drink lol.
Im thinking about making the head as a removable dome now. its not that much work and lot easier to machine in the software than afterwards

[wobbly]

The angle into the bowl is not very critical, I have used angled sides as well as a radius that ended almost vertical - depends upon the chamber geometry
needed to get the volume correct.
Just make sure, as I said before to clamp the outer flange, and use the water jacket cover to support the plug sealing face ( the step with an Oring in my section view).

[wax]

yes i saw that in your drawing and i have a heap of room to allow me to clamp the face down on the head.
hanks for that
Back to the drawing board literally hahaha
Thanks Wobbly

[lodgernz]

Just an aside: Did anyone notice that the British 50cc acu freetech championship was just won by an RG50, in the original frame?

[FastFred]

Did anyone notice that the British 50cc acu freetech championship was just won by an RG50, in the original frame?

Yes, and we have one or two here........

[F5 Dave]

Ya what? Was Marquez riding it? To them an RG is an exotic (post classic) import and Derbi or RS common.

[jasonu]

Ya what? Was Marquez riding it? To them an RG is an exotic (post classic) import and Derbi or RS common.

Maybe it was running that bridged exhaust port cylinder Chris Pickett made...

[lodgernz]

Ya what? Was Marquez riding it? To them an RG is an exotic (post classic) import and Derbi or RS common.

Hudson Kennaugh riding.
https://www.facebook.com/hudson.kennaugh.1?fref=gc
Scroll down a few posts until you see photos of a red and green number 50. There are videos of the race there too.

[Nath88]

For anyone interested, I did some further testing on the ion sensing system, choking the inlet to induce a misfire... I expected the measured ion current to drop to zero like it does with a four stroke... of course it doesn't! I think because the exhaust gas isn't purged from the cylinder every cycle like in the four stroke, the ions from the combustion are still there for the next cycle, whether there's fire or not, which seems obvious now. Nothing is ever clear cut with the two stroke cycle.

So next step will be to make a circuit to capture the pressure peak each cycle, then feed it into the ECU for datalogging, I should be able to detect misfire with that method.

[TZ350]

I did some further testing on the ion sensing system, choking the inlet to induce a misfire... I expected the measured ion current to drop to zero like it does with a four stroke... of course it doesn't! I think because the exhaust gas isn't purged from the cylinder every cycle like in the four stroke, the ions from the combustion are still there for the next cycle, whether there's fire or not, which seems obvious now.

Very Interesting.

Nothing is ever clear cut with the two stroke cycle.

I know your pain........

So next step will be to make a circuit to capture the pressure peak each cycle, then feed it into the ECU for datalogging, I should be able to detect misfire with that method.

I am following this with a great deal of interest, thank you for your work and sharing the results.