Proper compression ratio for an m20 turbo

[skete13]

Im finding so little online with actual numbers about the best compression ratios on turbo m20's. Does anyone have some m20 turbo setups and their specs and output numbers? Im trying to decide what kind of compression to use. Still in the early stages of a rebuild.

[matt325is]

Hi, my overall compression ratio is about 8.0:1. I'm using a 524td crankshaft, stock forged "i" rods, and forged alum Ross pistons (custom for low compression). My current output is ove 300whp. The last time I dyno'd I was at 267whp, but my small 2.5" exhaust killed my power (backpressure and detonations). Now with 3", it is MUCH more powerful, and can run more boost without detonation.

I'd say for m20's, anywhere from 8.0-8.5:1 would be good, if you are planning on running a LOT of boost, you may want to go with 7.5:1, but thats really not necessary, unless you are building a race car (+25psi).

Here's my website, still under construction.
http://matt325i.home.comcast.net/webpage/part2.html

For much more info, go to teh forum at http://www.e30tech.com . This site has the most guys with turbo m20's. Lots of info.

matt

[Bylund]

Here is some usefull applications for calculating the compression ratio.. it all depends on how much power u want.. and the purpose for the setup...
http://www.turbofast.com.au/freesoftware.html

[skete13]

Good stuff thanks alot.