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In Reply to: Re: Compression revisited -- 145-155 or 200psi? posted by Greg I on January 08, 2001 at 01:27:48:
Perhaps there is sufficient carbon build up on the pistons (and valves?) that the compression is greater than the good book suggests is normal. Have you had a leak down test performed?
Yes, had a leak down test performed. Perfectly normal. As I said in the other post, the car puts down 170HP to the wheels, which is about right on for what I have (Dinan chip).
I mean, we're talking about a 25% difference in what the site suggests and my (and some others) results. I would not expect the engine to be performing as well as it is.
Someone else said their dealership also stated 200psi as normal.
Greg.
Greg
A compression test is NO indication of your actual compression ratio, this in combination with a leak down test will however give a good indication of the health of your engine.
If your battery was able to spin the engine over a little quicker then it is likely that the reading would differ. An EVO II will probably have a lower reading than a standard engine even though the compression ratio is higher and the EVO III will certainly be lower. Why ? becuase of the cams and their 'trapping efficiency' at very low rpm (cranking rpm) put a wilder cam in and the inlet valve closes later and at that rpm the piston will just push the air right back out the inlet track and show a lower comprssion test.
All these variables will alter the results if you are making good power and all the results are consistent, the leak down is good then don't worry !
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