View Full Version : Good compression ratio for us??

Tbirdsc Colonel
05-23-2006, 01:28 PM
More or less have everything done except the lower engine. I was thinking of shooting for between 9.1-9.5:1 thoughts suggestions critisms?

David Neibert
05-23-2006, 01:36 PM
I like stock compression ratio of 8.2:1 because it allows you to make more power on pump gas without detonation than the higher compression ratio your considering.

If your planning to run on race gas then the higher compression motor will be capable of making more power. So it really depends on how you intend to use the car.


05-23-2006, 06:08 PM
Or if yoru running alcohol injection. I believe Kevin Leitman is running 10:1 and on pump gas. ALot has to do with timing and amount of boost..You may want to ask him

05-23-2006, 06:31 PM
I have been running 9.3-9.5 comp ratio for about 6 years now.It runs well with a tune.A higher compression ratio means better fuel economy,about 4-5% better by raising comp ratio by 1 pt.You will need to have a good intercooler and a tune helps greatly.

05-23-2006, 09:45 PM
Octane plays a role in what compression ratio you can run without detonation. the higher the compression ratio you can run without detonation, the more efficient combustion is, and thus the better your fuel economy.

Now for us supercharged folks, you want to balance compression ratio with the effective ratio that is created at max boost. I wouldn't recommend running more than stock without a tune. I'm going to be running about 9:1 once my engine is put back together.

I noticed XR7 Dave has a group buy for rods and pistons and the pistons are a lower compression ratio. Maybe he's been learning something over the last few years of tuning that has him recommending that.