Ovalizing the SI 24

[morbin]

Hi all,

I'm trying to understand how to ovalize my SI 24. I have problems with German (DA...) I'd like to know if there are some posts with some nice and easy pictures...

Will my Polini 177 with GS piston & Gravie's head benefit of this?

Thanks a lot,

Gruss

Matt

[haan]

take a look at

www.nuschool-riders.com

there you sould find some pictures

bye jochen

[micha2802]

Hi, it seems the server is down but you can download the "Original-tuning" instructions from here:klick here. It includes everything you need.

@Jörg

Hoffe es stört Dich/Euch nicht daß ich die Anleitung verlinkt habe.

[freakmoped]

ist ja sinn und zweck der sache

neue version 2 in arbeit - höchste zeit

nuschool riders server doesn´t exist anymore

i´ll build a new page in a few weeks, months...

[morbin]

Thanks all.

The pdf file is very interesting.

So if I understand right the ovalizing takes place only at the bottom of the carb, right?

[Green Bastard]

That's right!

[morbin]

Ok, now I see.

Anyway a question is coming to my mind... I knew that the valve area must be the same size of that of the carburettor (or at least a little smaller in order to make gas flux faster...). SI 24 area is 14*14*pi = 452mm2 therefore I should go for such an area on the valve (if valve width is 11mm length is 41mm, if width is 12mm length becomes 37.7mm, with 13mm length is 34.8...).

Ovalizing then makes internal area bigger than carburettor area... so is ovalizing helpful to make valve area bigger, is this done only to switch in any moment to let's say a PHBH 28 or this is done for blowback issues?

Gruss,

Matt

[morbin]

up

[sulei]

well with ovalizing you elimante a trush as your gaspillar is not slowed down. More gas flow needs more space so you have to enlarge the rotary valve area. theres an influence for the timing when you wide the inlet into rolling direction.

but i think the sprayback will be the same because of the turbulences from the cutted gaspillar.Maybe the sprayback isn´t that hard because of the slower flow.

But actually i´m a reed valve driver so the sprayback is anyway no discussion. Maybe i told you something wrong but this is my opinion at the moment for that story. Someone else a better idea or more detailed knowledge?