Compression test results?!

Grant_GTiR

New Member
I'm hoping people on here may be able to help me, after my turbo blew oil through the compressor seals for the third time i have decided to stop blaming the turbo and am now looking into the engine.

To that end i have just carried out a compression test on a hot engine with the following results:
Cylinder 1 2 3 4
Compression(psi) 141 133 142 141

The problem is i can't find a definitive answer on whether these are any good, they seem a bit low which would explain why i only get oil as the boost pressure builds up. Also the engine is fitted with a HKS 1.2mm head gasket (not sure if this affects the results).

I have also tried checking that the oil return from the turbo is clear by pouring oil down it which hasn't backed up so i believe it is clear.

I'm starting to clutch at straws now as i'm coming to the end of the project and this is really frustrating.

Thanks in advance for any help anyone can offer.
 

Fusion Ed

Active Member
Oil pressure isn't related to engine compression test results.

Have you (accurately) measured the oil pressure in the pipe that feeds the turbo, or any other part of the oil system for that matter.
 

Fast Guy

Moderators
Staff member
Book figure is 164psi standard, 135psi minimum. Difference between cylinders 14psi. So although you're just out of limits on 1 cylinder, I personally wouldn't bother about the 2psi just yet. If you want to it's up to you. It might be worth putting a new set of rings on if the bores are OK. That would give you a chance to make sure the pistons are OK as well.

Are you just getting clouds of smoke? Have you checked your breather system isn't blocked?

I allegedly have a knackered turbo, but I 've never seen a whiff of smoke yet. I have a Forge breather on mine, not the standard one.

You're not overfilling the oil are you? I did that on an old montego and the first time I thrashed it I got a big smoke screen out of the exhaust.
 

Grant_GTiR

New Member
Oil pressure isn't related to engine compression test results.

Have you (accurately) measured the oil pressure in the pipe that feeds the turbo, or any other part of the oil system for that matter.
One of the theories was that crank case pressure was building up and backing up through the turbo causing the seals to go, sounded a bit far fetched to me but i'm getting desperate.

The oil line has a reducer fitted due to the turbo being a GT30 series turbo, i think i'll have a look at the breather system next, there's no oil carry over in the catch tank, but i have changed the system since undertaking the project.

Could the thicker head gasket account for the lower compression??
 
P

pulsarboby

Guest
you have a worn engine there buddy!
hks 1.2mm gasket is same thickness as oe gasket when compressed so really your looking for higher readings than what you have there.
as said this has nothing what so ever to do with oil pressure but my guess is as karl suggests, being worn rings or possibly a cracked ringland on no2 cylinder.
 

Smo

Active Member
Sorry to hear it mate, hopefully you can get this sorted with minimal agitation! Don't you give up though.
 

Fast Guy

Moderators
Staff member
It's the part of the piston between the piston rings. The rings sit in a groove, the land is the raised part between the groves and also the part above the top ring.


 

009gtir

New Member
I was told my motor that was shipped to me was 180psi all the way across the board....is this a lie or just really good thanks!
 
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