130 compression on all cylinders

[karmakaze]

i did a compression test on my engine and got 130 across the board. i know the minimum is 128.

but my questions is, do i have anything to worry about? the important thing is that it is all the same right? would wear on the engine make them all that low?

i am going to redo it tomorrow and pour some oil into a cylinder and see what happens and check to make sure my gauge is reading right just to make sure.

is it possible i got lucky and that my engine has a thicker head gasket installed? that would affect these readings wouldn't it and it would explain the even numbers?


Modified by karmakaze at 12:07 AM 3/8/2006

[AmoebAssassin]

Did you do the test warm, using the starter? Or did you do it cold, or with hand-cranking?

[karmakaze]

warm with starterhowever, i did not depressurize the fuel system.

[Dori Dori]

Seems odd they'd read low across the board. Maybe you do have a thicker HG although IDK how much lower it should read with one. Maybe try a different gauge if you have access to one.

[karmakaze]

Seems odd they'd read low across the board. Maybe you do have a thicker HG although IDK how much lower it should read with one. Maybe try a different gauge if you have access to one.

tried a different gauge. it read a few psi lower, but i don't trust its readings because it has a design flaw that makes it hard to secure firmly into the spark plug socket.

however, i did stick an extra o-ring on my first gauge and depressurized the fuel line and it read 35 across the board.

and upon further inspection, i took a look at my head gasket, in the very front of the engine there is this place were a few tabs stick out and i am pretty sure that this is an aftermarket head gasket. it is 2 pieces of steel (what i am guessing to be stainless) with fiber inbetween. the stock one is some paper like material isn't it?

what i don't get is, why would you put an aftermarket head gasket on the engine and not put anything else? when i got the engine it was bone stock. unless osaka took the aftermarket stuff off and put stock back on??

i also found this zerothread?id=112393but he does not specify what size HG he is using.

so i sort of wonder what size HG i have. *goes off to borrow a micrometer*

[spider_slayer]

stock headgasket is carbon paper i believe. metal tabs indicate that it most likely is an aftermarket headgasket.

[karmakaze]

well i measured it and came back with about 1.4mm is that measurment on a head gasket the size when compressed or as is?that so rocks.

what would you guess the chances are that anything else has been done to the internals?

i am not going to open up the engine and check, but i would think the odds are fairly good.

[S13240]

126 psi is minimum per fsm and if all cylinders are within each other...it just shows that they're all detiorating altogether slowly.

[karmakaze]

126 psi is minimum per fsm and if all cylinders are within each other...it just shows that they're all detiorating altogether slowly.

what fsm are you using? lolmine says 128psi.

the likelyhood that all cylinders are deteriorating within the exact same tolerence is very unlikly.

and the fact that i now know that my car has a 1.5mm head gasket explains the compression being on the low end of the spectrum. a thicker head gasket will decrease compression.

[TheSparo]

it wouldn't decrease it that noticeable... you see how little 1.4-5 mm is... not a big difference... not like 10psi

[karmakaze]

when your talking about height, no, it isn't very much. but when you start talking about volume and circumference it can be.

there is not any definite numbers on what the compression ratio should be after going with a bigger or smaller head gasket at least that i can find. but either way, the numbers are solid across the board on my engine and its very unlikly that the wear would be that even. and since there is a 1.5mm head gasket on the engine, i have no idea if anything has been changed on the inside.

how about some of you guys with thicker headgaskets post some of your compression tests so we can have some numbers to reference.

it wouldn't decrease it that noticeable... you see how little 1.4-5 mm is... not a big difference... not like 10psi

[Vr6WantSr20det]

when u did the compression test u disconnected the CAS and held open the throttle fully? When i first did a compression test on my s13 sr20 i didn't open the throttle body and got 130psi accross. After i tried it again with the throttle open all the way and got around 150-155psi on all cylanders.

[karmakaze]

i did not disconnect the CAS but i did have it held at WOT.why would you disconnect the CAS? that has nothing to do with a compression test?

[Vr6WantSr20det]

with the cam angle sensor disconnected the engine wouldn't start. Is the motor currently running/installed?

[karmakaze]

with the cam angle sensor disconnected the engine wouldn't start. Is the motor currently running/installed?

ah, i just disconnected my ignitor chip.

i have had it running. at the moment i have everything pulled off of it though.

[nv240fastback]

I just pull the fuel pump fuse, then hold the pedal wot and crank the motor like 3-5 times.

while its cold.