Hot Compression Question!

[ViciousVendetta]

Hey guys, just got my compression tested and heres what it is...

180 - 170 - 175 - 185

When it was done cold the numbers were around 160 or so... A factory compression test is done when the engine is at running temp, correct?

Now is that good compression? And are those numbers indicative of Arias 9:1 forged pistons being in the engine? I bought the car with a supposedly built engine and knowing if it actually does have hig compression would set my worries to rest... Thanks fellas!

 

[larryriverside]

come on! i think you know the answer to that.

 

[ViciousVendetta]

...

I wouldnt have asked the question otherwise...

I just want to know what others think, maybe to give me a little peace of mind. To me the 170 - 185 seems like a big jump, but i dont know that much. I dont know the stock engine compression for a 1g awd, nor am i totally sure if manufactorers get their stock compression specs when the engine is cold or at operating temp. I have an idea for some answers but I just want to know for sure, and to have an idea if those numbers really would match up for having 9:1 comp pistons. I guess im weird like that, but treat me and let me know what you guys think!

 

[Mike 99GSX]

Well 2g compression ratio (8.5-1) pistons is supposed to be 178PSI so I'd say you're maybe just a tad low but not to bad. I'm sure someone here with 9.0-1 can chime in. And yes you are supposed to do the test while the engine is warm with the throttle plate all the way open.

 

[98TsiAWD]

Like he said 8.5:1 stock 2g compression is 178psi, so your engine has a VERY little amount of wear. I would guess that 9:1 compression on a 4g63 should yield about a 190psi compression per cylinder.
You should be just fine.