Porsche Enthusiasts Club Forum

Hi all,

I hope someone here can help me interpret my compression results:-

1-180
2-190
3-200
4-210

On the one hand I'm glad I haven't got low compression, but it seems a bit weird they go up in 10 psi increments front to back. I did have the head skimmed when it was overhauled a few years back so I was expecting to have slightly higher compression but this seems a lot higher than the 145 quoted in the Haynes manual. I don't use much, if any, water or oil. So perhaps leaky injectors?

That is very wierd!

It shouldn't make much difference but did you do the test with the throttle open or closed? I guess leaky injectors may cause that. Have you tried measuring the compression the other way around.

If I am honest, with that array of wierd results (Compression testers IME only tend to give a vague ideal) I would drive it and enjoy it .

Hi,

As per the instructions on the box I held the throttle open, do you think its worth trying with the throttle closed?

Once getting those results I did go back and test no. 1 again and got the same result.

When I do a comp test I dont start the engine. How would a leaking injector have any effect as it is outside the cylinder, or am I missing something.

Tested a friends Nissan 300 twin turbo recently and the tests did vary a bit and even on the same cylinder.

drop of oil down the plug hole seals the rings a bit to see if its the valves or rings leaking.

Yours does seem high.

Glazed bores? A slight drop of compression? Sure it will eventually build it up again, but when is the question. My Stag had this happen almost all of the time initially with the Holley carb. It would spin very freely until eventually the cylinders built up compression once more from the petrol going into the bores as a result of the fuel being heated up in the carb as a result of it being stood.