I am building a new motor for my car when I get back. I am just wondering if someone could give me some good information on the effect of compression in a boosted engine. That being specifically in a drag car scenario.

What would the benefits be of running say 11:1 compression and 30psi vs 9:1 compression and 30psi?

Thanks

 

11.1 on 30psi is kaboom vs.9.1 on 30psi ..9.1 will give u more room for your 30lbs...tuning is the key

 

lol that was funny

 

Not true, not true, true.

 

I agree... I think kutsujus2k and Tony just proved that since the stock S2K is 11:1.

More compression is just that... more compression of the mixture = more potential energy. You'll get more power. Just have to tune correct.

 

More compression is less opportunity to control heat.

 

...the simple answer is being able to make more power, but having less room for error when tuning. So, if you have a good tuner, its all good. If you ask Miller he will tell you that using that mix is nothing new.

 

we generally do 9:1 on pump gas cars and 10:1 on race gas cars. i run 10:1 compression on my car at 50lbs of boost.

i had a personal turbo car of mine that was 12.5:1 compression. ran it on 110 octane gas. 20-25psi of boost. not ideal....but it was fun.

 

We run 12.5:1 on our sunfire. I know of some local guys that are running 12.5:1 on gas with turbo and squeeze that are making some real good power. Were planning on switching to 11.5:1 on our crx.

 

High Compression ratio has a overall higher thermal efficiency. I always say that low compression engines are for people who cant tune. These same people probably rely on knock sensors also. lol

Also, camshaft design plays a huge roll in compression ratio (dynamic)

 

I guess my real concern is the difference in power worth it?

I am looking at either 9:1 or 10.5:1 compression ratios. Is it worth it to use the higher compression or go for more boost to make power?

The car will be ran on c16/q16. It will be built specifically for the strip. It will also be tuned by someone competent...undecided who exactly right now.


Also, what are your feelings on using spray in a boosted application like this? Is it complicating things too much? I know I will be limited on these engine because of a revability issue, as far as turbo size. I was thinking about using spray to pickup power, say 100hp on top of the boost.

 

I think with as advanced as some of the manifolds and turbos on the market you will be fine with just 1 power adder. Spool and top end on some of these monsters doesnt seem to be a problem.