Does anyone no what pressure I should be getting on a 95 WRX and how many times should I be turning it over while doing the test. Also What number pistons are what i.e. 1 2 3 4 and how do I stop it starting while turning it over.

Reason I ask is I have a compression gauge and don’t really want to pay someone to do it.

 

I don't know the exact figures, but a margin 5-10% of the highest pressure recorded is a good ballpark to start with.... Usually, (from my experience, limited as it is) if piston damage occurs, the difference is very noticeable between that and the other healthy pistons.
Why are you doing a compression check? Routine check or something more pressing?

 

Disconnect the crank sensor and have someone hold the throttle wide open.
Crank the engine until you get the maximum steady reading on the gauge.
You should have somewhere between 140 - 170 psi per cylinder with a maximum difference of 30 psi between the cylinders on a healthy engine.
The cylinders are numbered as below







Mick

 

Cheers guys that’s a great help.

I’m doing it because ive had some problems with oil coming out of the dump valve and the air filter. Also there is a little bit of smoke coming out the exhaust when you start the car.
I put thread up a while ago asking for some advice and it seems the most likely causes are either the turbo oil seals or a damaged piston..
Hopefully the compression will be ok and it will be the turbo. If not then ive got big problems.

 

Mick
I need to do the same with my classic with a 2.5 bottom end as the thing is drinking oil. Do the same PSI figures you quoted above apply to a 2.5?

Thanks

 

isar - yes the figures are the same for the EJ257 but the maximum difference between cylinders is 15 psi IIRC.

Mick

 

Hope we both haven’t done a piston.
Good luck mate.

 

Thanks merlin

Good luck to you too Chris - fingers crossed for it being the turbo.

The car drives fine and hits big big speeds on the autobahn....but boy does it use oil - way too much!

We shall see! Good luck anyway mate