91 Galant VR4

[Murlo26]

There are two thoughts on how to make power on alcohol.

9:1 worked last year so I will stay with that. I can still turn the boost up for more power.

If your turbo has more boost in it then yea I wouldn't go for higher compression. I remember I asked Shane about this back when I was thinking of going 10.5:1 on my car and he said the only time it makes sense is when you are trying to max a turbo that is out of air.

Well seeing as how I don't want to get out of a stock frame I settled on 10:1.

I would be afraid of running higher compression on a setup like this. So many other parts to break, I think staying 9:1 is prolly a good idea even if you could make a bit more power on higher comp.

Hopefully its a good year for this beast.

[Pushit2.0]

The power started to drop up top a little at 44psi. Its well known on a 2.0 and a 4202 will make over 50 psi. I think at 46-48 psi the car will be close to 4 digits.

~John

[turbotalon1g]

There is a limit to compression I agree, but from what I've seen its closer to 11:1.1
on 4G63.

Like i said, i'm sure u don't want to buy new pistons just for that, but down the road you might consider it.

[Shane@DBPerformance]

I would rather run 50psi with 9.0:1 compression than 30psi with 11.0:1 compression.

[Goat Blower]

I would rather run 50psi with 9.0:1 compression than 30psi with 11.0:1 compression.

I'd rather run 70 psi with 7.0:1 compression than 50 psi with 9.0:1 compression or maybe go really crazy and run 100 psi with 3.0:1 compression. Everybody's doing it.

[Kracka]

Higher compression always seems like a great idea on paper...then blows up in real life.

[Shane@DBPerformance]

I'd rather run 70 psi with 7.0:1 compression than 50 psi with 9.0:1 compression or maybe go really crazy and run 100 psi with 3.0:1 compression. Everybody's doing it.


Hell yea, someone used or maybe still does make 7.5:1 compression pistons for DSMs. Boost makes more power than compression, and compression does not spool the turbo any faster.

[turbotalon1g]

Higher compression always seems like a great idea on paper...then blows up in real life.

Everyone on the link forums seems to be doing ok, so good infact that wiseco is releasing 2 new lines of higher comp. pistons.

[Murlo26]

Everyone on the link forums seems to be doing ok, so good infact that wiseco is releasing 2 new lines of higher comp. pistons.

Yea most new builds I have seen that run corn or race fuel always have high compression pistons and I don't see any problems popping up.

The only problem I have seen was plano evo's...doesn't mean high comp is bad.

[JET]

Any time you compress air it will heat up, the great thing about higher boost is that you then get to cool it down with an intercooler. When you raise the compression you do not get to cool the air down, so more heat is created. As with everything there is always a happy medium and alcohol burns cooler, so where that happy medium is... that is the question.