Compression test, good results i think.

[89Turbo]

so i was changing my spark plugs and thought why the hell not. Read somewhere that that need to be 148psi as least each with no more that 15psi difference so i think these are alright, little high but im not sure what that means.

Cyl 1:155
Cyl 2:160
Cyl 3:160
Cyl 4:160
Cyl 5:155
Cyl 6:160

i know they're in increments of 5 but the compression gauges arent that accurate.

 

[MKIIINA]

looks good overall to me! variance is well within spec and id say everything looks good man!

 

[Idealsupra]

:bigthumb:

 

[89Turbo]

sweet, my old plugs were horribly gapped to, so these new ones i put in (NGK 3330's) were gapped to .29-.30 and my EGT's went down a bit, so im very pleased.

 

[suprarich]

Did you remember to do the test with the fuel pump shut off?

 

[89Turbo]

Did you remember to do the test with the fuel pump shut off?

nope.

 

[suprarich]

That will raise your numbers because you are adding an extra element to the test. Also, should be done at operating temps.

 

[89Turbo]

That will raise your numbers because you are adding an extra element to the test. Also, should be done at operating temps.

it was definetly done at operating temps though.

 

[theprodigy79]

This may be a stupid question, but what are the factors involved in the numbering in a compression test? I know that usually the higher the better, and I know they should not fluxuate more than around 10% per cylinder (ideally less), but what is the highest compression possible?

I ask because you all are saying those numbers seem good... but I just had a compression test at the Toyota dealer on my car with results of 175, 170, 175, 175, 165, 170 (normal operating temps, fuel pump off) and found out that I have a blow(ing) head gasket... A N/A Supra I had checked out before I bought mine had compression for all cylinders in the mid-to-upper 180s and a couple in the low 190s, which was supposed to be excellent...

Thanks,

-James

 

[CzA]

theprodigy79

Now i may be wrong but you're getting higher numbers because the compression ratio is higher on N/A cars than Turbo cars. Please people, correct me if I'm wrong.

 

[jetjock]

N/A spec is 156 while the turbo is 142. No more then 14 difference between cylinders. Assuming the engine hasn't been modified higher pressures are usually due to deposits. It's always better to check the book rather than go by "read somewhere" memory what specs are. Even though a compression test has to be one of the most basic procedures done to an engine had the OP consulted the manual he'd have seen he was doing things wrong. An EFI engine requires the disabling of fuel and spark when doing compression testing or damage can occur. Any engine should have the throttle blocked open.