What Causes Low Compression?

[rad100]

just looking at causes to how engines develop low compression..

also does low comp in a cylinder cause missfiring?

i got results of

150

150

150

150

130

150

now would this mean rebuild? and would this cause missfiring?

rb25det s2

apexi turbo

power fc

nismo 550cc

eboost

z32

3inch turbo back (gutted 3inch cat)

hks exh cam gear

tube and fin cooler

splitfires

plugs put in straight from box not gapped

any ideas would be great!!! cheers in advance..

[mitchy_]

plugs put in straight from box not gapped

might be a good idea to check the gap...

[super_s13]

Do a wet comp test on that low cylinder and see if the result changes. That will tell you if its a big problem. Failing that it looks ok to me.

[bnr#@]

It is out by more then the 10% recomended max but not by much, I wouldnt stress about it yet. No, that will not cause your missfire

[rad100]

ah k, so ill gap my plugs and c how we go.. if that dont work anyting else i can do while the engine is pulled apart? lol..

cheers all.!

[sly32]

i would be worried with number 5 cyl down 20psi compared to others, even if all cylinders were on 130psi i wouldnt by the car, not with a rb anyways as comp standard is 170psi,

as for making it loose compression, there are lots of things, but i know for a fact that its normally 5 or 6 that goes from memory? why would this be?

i thought you get alot more wear if the engine leans a bit, screws the rings and/or melts pistons,

JV

[rad100]

hmm... would there be any signs to say that its affecting the car?

coz besides the missfire its GREAT!

[sly32]

nar wont have anything to do with a missfire, your miss fire is most likely either coilpacks, or spark plugs im thinking,

[Bennett]

Souldnt be any obvious signs from those compression readings although you could be making more power if they were all 150 but mot by much.

Lost of peoples cyl 5 and 6 lose compression when they have front facing aftermarket plenums as they are deprived of air. Is your intake plenum stock?

Also if your missfiring is really bad and has been there for ages on the same cylinder could it have caused the low compression?

[(OO)Firty Free(OO)]

As stated above re-gap your plugs. I'm running BCPR7ES copper plugs gapped to .65mm @ 18psi with standard coilpacks and no missfire issues.

[CRoNic...]

15psi variance between the cylinders compression is considered fine.

[rad100]

ill be re gapping on fri ill let u know how it goes... thanks all