well I just bought a brand new compression tool at advance auto. got it home, started on the driver side closest to the radiator. took the plug out, compression tester in, tried to start her up. it was 180/12. I specifically asked the guy if the 1-20 pretty much meant 11:1, 12:1, etc and he said yes. So now I'm thinking 12:1 on my car, no way (no internal mods done). I checked the entire drivers side and got 180/12.

Wasn't able to hit the passenger side b/c I had a date.

I have a 1994 Z28 A4 and the ONLY mods I know of aren't that big. ummm CAI, !CAT, flowmaster muffler, MSD 8.5MM SC wires, Bosch Plat plugs, and that is all. No internal engine mods that I know of, I bought the car used.

Also last year before I had ANYTHING done to the car, it was running 8.5s. Nah just kidding. It was running 9.3s and 9.4s consistantly. Since then I've did the CAI, !CAT, muffler, MSD wires, & plugs. Haven't ran it yet.

Just wondering if you guys can give me some help on that compression tester. thnx

 

From my experience with compression testers, it's almost impossible to even get close to estimating CR from the pressure gauge reading. 180-190psi isn't unusual for a 10.5:1 LT1. But the pressure you get will depend on a number of factors, including the number of strokes, how far open the throttle blades are, the temperature of the piston and block, presence of fuel or oil that seals the rings, etc.

The meaningful part of the compression test is not the absolute value... its how much the numbers vary between cylinders.

Some interesting info on compression testing

 

wow great article.

after reading this is what I came up with..

180 reading really is good. The article states if you test the compression when its cold then it will read low, which from 170-200, 180 is low. But mainly what I was going for was consistancy. All 4 cylinder on the drivers side was from 179-181. I still need to hit up the passenger side which might happen this weekend.

Thnx for that article.