skratch77

After talking to taso over in the middle east he said car should see 170psi on semi hot engine.

I just did 3 cylinders and I'm getting 212 psi on each so far.

if this is high it can explain why my car dosnt like anything over 25 degrees timing

sventastic82

At 80C (176F) it should be between 14bar (203psi) and 18bar (261psi). Difference between cylinders shouldn't exceed 2bar (29psi)
Looks like your compression is on the low end but could be temperature related.
Not sure where Taso is getting his number from but 170psi (at operating temp) seems to be very low and should trigger a leak down test.

skratch77

the engine sat about 2.5 hours before doing the test. I was taking out my plugs to scope my cylinders after running fuel cleaner and decided to run to the store to buy a gauge to test.

Do you know the numbers on a cold engine? I can test that easily now

sventastic82

That is hard to say per Mercedes the test has to be performed at operating temperature.
Due to the Piston expansion it can vary from 10 to 15 psi on cast pistons. The P31 engine having forged pistons that could be different in most cases. Forged pistons have a higher expansion rate and therefore the pressure difference in a P31 car between cold and warm could be higher.

I would perform the test at operating temperature to be sure.

skratch77

I knew you were going to say that lol I started taking the manifold off to install thermo spacers.

I'll have to retest when it's back together

sventastic82

You can continue to perform it cold and go for the pressure difference between each cylinder. I would say 212 on a cold engine is pretty good.
I’m not sure if your compression can be too high.

I have nerver seen an engine with a too high of a compression. But that is just what I have seen so far.