Interpret compression/leakdown #'s

[pantera]

I received my test on compression/leak down diagnose.

Compression

1=145 PSI
2=135
3=135
4=145
5=135
6=140
Leak down
1=1%
2=2%
3=2%
4=3%
4=3%
5=2%
6=5%

Why wasn't the PSI kept constant for each cylinder and what PSI is optimal for compression test? What do you think of these numbers for a 116,000 non rebuilt top end?

Many thanks, Dan

[Henry Schmidt]

You win. Those numbers are great for a car with those kind of miles.
Because of the tendency for carbon to fall from the spark plug (removed to do both comp. and leak test) to the exhaust valve you rarely get perfectly consistent leak down or compression numbers.

[pantera]

Thanks Henry, I'm trying to get acquainted with these engines being that this is my first Porsche purchase.The owner was really on top of maintaining the car. The car was used for DE's and I was a little skeptical about the outcome of the test. I never heard of carbon deposits falling into the valves from plugs being taken out. Are these engines that have little or no maintainence or have oil blow by?

Still not sure why different PSI was used for different cylinders?

Thanks, Dan

[Henry Schmidt]

Originally posted by pantera
..... I never heard of carbon deposits falling into the valves from plugs being taken out. Are these engines that have little or no maintainence or have oil blow by? Dan

All engines get carbon deposits in the combustion chamber.

Originally posted by pantera Still not sure why different PSI was used for different cylinders?

Thanks, Dan

What does this mean? If your question is "Did Porsche build the engines with different comp. ratios for different cylinders in the same engine ?" the answer is no. When new, all the cylinders in a given engine had the same comp. ratio.