Cast Omegas Pistons for Turbo use
Turbo Mini Forums

Hi, im finally getting close to the stage where i will be building my motor, would appreciate some advise from those with experience:

I have a set of 73.5 low compression height 11cc cast Omegas, i am planning to run these in a turbo 1380.

Comp ratio works out to 8:1, and i would like to run around the 15psi boost mark.

I have had a rough measure of crown thickness to be 5.7mm, do you think these pistons will be up to the job,

Thanks in advance

Low comp height pistons woule mean that the crown is miles from the top of the block at TDC. NOT good for combustion. Do it properly, get some correct pistons.

What are these low compression high pistons good for?

If i put them in a short stroke n/a engine and skimmed the block to suit, what would be the downside?

the low height ones should be ok in my experience, my mate runs a set of low height forged flat top omega's at 8:1 and is around 200 banana's.

wouldnt a low comp hieght piston in a short stroke motor just put the pistons even further down the block? so even more skimming?

for every 0.010" down the bore from TDC is .... 1cc on a 1380 ..... so add a further 22.4 ccs into you calcs

you can get the boost rigth up there if you wish!

Yes they do sit very low in the bores, 1.6mm down, which is why i can get the compression ratio so low with 11cc pistons and 28cc head
I beleive there originally designed for long stroke cranks?
But what im worried about is will they take the boost?

yes! the cast omegas are well proven with over 20 psi of boost.

no worries in the quality of them whatsoever

Cheers Steve, thats what i wanted to hear! Should finally get round to using that cracking head you did me soon!

What problems, other than poor combustion, are associated with running pistons so far down the bore?

In the 13's at last!.. Just

Cheers V

In the 13's at last!.. Just

Vegard, what are your thoughts on running the pistons above the deck head, assuming you can get the CR required?

Team Racing

A little bit above is good for squish, although too much and you know what happens under high RPM. It also depends on the squish band on the pistons. Too wide and one may actually get pre ignition from the locally very high pressure toward the outside of the squish band.

You know why your miglia engine builder have his name right?

Edited by miniminor63 on 20th Apr, 2009.

I know for a fact that this is what top racing engines do, but rod-stretch will be an issue with a high revving engine, and also with a big bore as the gasket is smaller in diameter. Anything to get maximum squish.

However, if you're running 50psi this all alters judging by various books concerning GroupB rally cars and F1 turbos.

Team Racing

33psi!!!! How much power?

If something is worth doing, it's worth doing half of.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

that was on only 24.47 psi though...

Still 25psi is impressive.

If something is worth doing, it's worth doing half of.

the cast omegas will be good , t3tone is running the same pistons for years in his 1380 turbo

always looking for them bigger bunches of bannanas

Cheers for advise turbo hogster

AlexF