That’s a bit high…(compression)

[CruiseGTi-R]

I get 185 185 185 179psi, cold. or ?

Plugs I took out had only a little white fluffiness on their tips, which I thiiiink is ok?. They were heat range 9, hinting at previous owner running highish boost perhaps.

Done a little search but not a great deal about high comp results.

I know there is more risk of det with higher comp, maybe my valve clearances are too big, or maybe there is fluid (oil/fuel) in the cylinders.

Other than that whats the deal with these sort of results?

 

[nismoboy]

tbh your worrying about nothing, it sounds healthy so dont worry. What boost are u running?

 

[CruiseGTi-R]

1 bar. Runs perfectly too .

I was happy with the readings being on the high side until I read a few posts and googled a bit.

Just a bit odd to be 20psi more than standard isn't it?

 

[Fast Guy]

You're not the first person to have those sort of figures, but I think you might be the 2nd I've heard of
You should do a compression test with the engine at normal running temperature

It could be down to cams as well, if it runs fine and doesn't detonate, don't worry about it. just enjoy the boost

 

[AJ4]

depends on what guage you used as well, for example, Halfords jobs aren't exactly accurate More important that they are all even than of a particular value ( unless its f**k all on all four cylinders )

 

[Rishi]

Standard should read in the 160psi but this depends on the guage and if the engine was warm... you will read higher from cold...


Rishi

 

[Dooie Pop Pop]

would oil contamination in the guage probe cause a higher reading?

 

[DOT2DOT]

you will read higher from cold...


Rishi

Why is this??? I always thought that the piston would have more expansion than the cylinder meaning less clearance and ring gap when warm???

 

[AJ4]

also, remember to disconnect the fuel pump relay, as any fuel injected into the cylinder will seal the piston and give higher than normal pressures.

 

[Mr GTiR]

After my rebild, ADR Motorsport (who did the rebuild) did a CR test and i got 185psi from a warm engine.

They were more than happy with that result.

 

[Rishi]

After my rebild, ADR Motorsport (who did the rebuild) did a CR test and i got 185psi from a warm engine.

They were more than happy with that result.

But thats different... They or you could have been aiming for that compression... Its not a case of build and just hope... :shock:

I had a dummy short block built just to make sure that the compression was as i wanted...



Rishi

 

[CruiseGTi-R]

I removed fuel pump fuse, started it and let it run out of out of fuel and checked again, same results.

I also could not for the life of me see any ring mark or numbers on top of the cylinder (although bloody hard to tell). Maybe its been re-built, who knows.

I'll have another go when its warm. Other than that its Optimax as usual and keeping out of high gears at low revs, keep away from det basically. Is knocking quite clear audible on R's?

Tell you what though, runs better on the new plugs. Probably just psychological, but definitely feels stronger.

 

[CruiseGTi-R]

I removed fuel pump fuse, started it and let it run out of out of fuel and checked again, same results.

I also could not for the life of me see any ring mark or numbers on top of the cylinder (although bloody hard to tell). Maybe its been re-built, who knows.

I'll have another go when its warm. Other than that its Optimax as usual and keeping out of high gears at low revs, keep away from det basically. Is knocking quite clearly audible on R's?

Tell you what though, runs better on the new plugs. Probably just psychological, but definitely feels stronger.