1G DSM with JDM Cyclone compression test

[tcpx]

Hi there,

I have recently done a compression test on my '91 talon Tsi with AT, the car itself has 191,xxx KM's so around 120k miles, but unknown KM's on the engine (probably lower than 120K miles im assuming, as most JDM swaps has less mileage...) and it is a JDM cyclone engine on it..
I got a reading of around roughly 135 on all 4 cylinders but I just remembered.. that when we did that test, it was actually without pressing on the gas pedal to the floor while cranking the engine since I forgot to.

My question is, would that have affected my compression numbers at all if I have done so? I might have to do a re-test soon... and also, is my engine in pretty good shape still?

 

[19Eclipse90]

Yes, it could have. You are supposed to perform the test with the throttle fully opened and with the engine warm. Your numbers are at least consistent, that is a good sign. Repeat the test and see if they improve.

 

[tcpx]

just got back from my friend's house, we redid the compression test before I changed the spark plugs and this time, while also keeping it at wide open throttle while cranking.. definitely did make a difference

I got these results, starting from the "left" cylinder
150, 150, 147, 147

so it's pretty much telling that my engine is still in prime condition right?

 

[19Eclipse90]

Well, not exactly prime, but good enough. Prime would be factory spec, mid 160's across, just so you know.

 

[tcpx]

yeah, I read somewhere that factory compression is 164 .. but I suppose its good enough. definitely would be "mod worthy" though right?

 

[19Eclipse90]

If all scheduled maintanence has been performed and you are satisfied with how the car is running, it should be safe to begin modifying. That is ultimately your call.