ESE's works engine tuner

[wobbly]

In my dyno testing of heads for a flat top piston I tried three geometries of chamber outer wall with the toroidal shape.
Each was optimized for ignition timing and best power egt.
First was a wall at the bowl edge of 90* that then formed a radius into the toroid roof shape.
This needed less ignition and a bigger jet , compared to the original flat roof semi tophat shape - background detonation level was considerably less , and power was up the front side nearly 0.5 Hp and around 1.5 Hp in overev.

Next was a radius all the way to the bowl edge that was 30* from vertical at the intersection.
This needed the same setup as above but made around 0.3 to 0.5 Hp more everywhere.

Last was a straight wall @ 60* up from horizontal , then forming the toroid roof radius - so the radiused roof was higher to achieve the same cc
This needed more ignition , and a smaller jet , but the power was much the same as the tophat example.

Squish and cc were all identical and had no radius on the squish/bowl edge , just the sharp corner broken with wet and dry.
I wish i now had the opportunity to try chamber shapes with the latest piston , having a conical squish , transitioning into a flat top with 50% bore area.
This is the shape I used in the BSL 500 , but only with a bathtub , as that is what Jan had found worked best at the time.

[Haufen]

So 90° was the best, followed by 60° and then 30°?
And the original was a flat roof bathtub style but with edges in the corners (tophat) instead of radiuses? Is that correct?

[wobbly]

No , the 30* tangent intersection with full radius all the way up into the toroid was best , it made a little more power than the 90* version - ie no vertical flat section before the toroid roof radius.
Sorry that wasnt clear the way I described it.
So , 30* , 90* then 60* = same as tophat ( but this toroid also had less background deto like the others over the tophat design ).
All tests had no corner rad at the bowl edge including the tophat.

[Gradella23]

No , the 30* tangent intersection with full radius all the way up into the toroid was best , it made a little more power than the 90* version - ie no vertical flat section before the toroid roof radius.
Sorry that wasnt clear the way I described it.
So , 30* , 90* then 60* = same as tophat ( but this toroid also had less background deto like the others over the tophat design ).
All tests had no corner rad at the bowl edge including the tophat.

thanks for the insight, may i ask you to post a pic or a sketch of a toroid chamber to understand what dimensions are you higlighting?
probably it's an english language understanding problem, i'm sorry for this... you can maybe draw them on the blue toroid prototype you posted some years ago

thanks again

[lohring]

This has been posted in the past.

Lohring Miller

[Gradella23]

This has been posted in the past.

Lohring Miller

Thanks Lohring. So i guess this is similar to the 30° version (30-7,5°?)
I'll obtain something like this: i can't find enough volume compared to the standard shape, even if I reduce a lot the squish band. (40mm bore, 0.45mm squish, something around 16:1). Am i missing something?

[wobbly]

What chamber cc are you shooting for - I will do a CAD sketch for you - maybe this setup would be best with a small thread plug.

[wobbly]

So I looked thru my files and found a TZ50 , this is 40 bore with 39.3 stroke.
With 16:1 the cc is 3.33 and squish is 0.42 and to get 38M/s MSV the width is 50% = 5.84mm
This uses a 10mm NGK race plug with Iridium fine wire electrode and a Platinum fine wire ground = R0373A - 10 the same nose configuration as the 14mm R 7376 that is the best
race plug in every other configuration.
As this isnt a flat top the chamber wall can be steeper to suit as the squish is also angled.

[Frits Overmars]

Wob, I noticed that your suish area radius = piston dome radius + squish gap. But in a running engine most of that squish gap disappears, which causes an (admittedly, miniscule) occluded volume at the outer edge of the squish area. Therefore I prefer to make the squish area radius equal to the piston dome radius.

[Vannik]

Frits, something just for you!

https://www.youtube.com/watch?v=M92nNsxe7W8

[Wos]

...so awsome listen to you experts 👍😯

[Frits Overmars]

Frits, something just for you!
https://www.youtube.com/watch?v=M92nNsxe7W8

A 700cc four-cylinder two-stroke on methanol without any form of supercharging except for the contribution of the pipe, putting out in excess of 350 Hp?
That's over 0,5 Hp per cc. That would be damn good from a 50cc single. But from a 700-4?? 'If something sounds too good to be true....'

[Wos]

Have my daughts too frits.
Too much friction in 750cc engine

A kreidler made 440 hp per liter in the 80ties

Aprilia Rsa 432 hp/ l

Best 50 cc today frits ?
Best prooven hp/ liter ever?

I ve heared about slightly over 26 hp on 50cc....ergo 520 hp/ liter...can that be true? 😉

Apropos... feavering for liedolsheim/ germany... 50cc 8H endurance Race in September 👍👍😲😎🥰

Wolfgang

[Frank S.]

Apropos... feavering for liedolsheim/ germany... 50cc 8H endurance Race in September 👍👍😲😎🥰

Wolfgang[/QUOTE]

I will be there
Who else?

[wobbly]

Frits, if you are thinking of the piston/head geometry changing , then we should be addressing the rock over at TDC as well.
And if we estimate an added 15% power due to Methanol then the RSA would be 506 Hp/L as a benchmark.
Thus the 700 is making very close to the same power per L , to me the pipes dont look clever enough to do this on a reed engine with 175cc cylinders.
But they will be measuring power at the crank , the RSA was at the sprocket , so a variation there in favor of the 700.