3s-ge Mr2 Mk2 (1990) Compression Results?!

[Emmy]

Hi all,

Just did a compression test on my MR2 (3S-GE N/A), and got the following:

cyl 1 = 248 PSI

cyl 2 = 248 PSI

cyl 3 = 238 PSI

cyl 4 = 260 PSI

Apparently "normal" compression is > 178 PSI, so my results seem pretty high! Is this still within established norms, or is my mechanical timing out (too advanced)?

Spark pliugs also look like they've been running a little hot too, which further reinforces the "too advanced timing" theory...

Thanks!

Shash

[Kelvyn]

Where does the 178 psi come from? I know the turbo is supposed to be around 165 psi but they are low compression engines. I would have expected around 200 psi. I think they are supposed to be within 14 psi so looking at your figures you appear to have a problem. My guess (worth nothing) would be that number 4 is oiling up slightly causing the higher compression. That could be worn valve stem seals (blue smoke first thing in the morning) or worn rings/bores (blue smoke if you leave it ticking over for 5 min then rev it).If you have either of these its not serious as the readings aren't THAT different. The mechanical timing you refer to I assume is valve timing. If thats so then incorrect timing can only decrease the reading. If you mean ignition timing that has no effect on compression. With your plugs are you sure you have the correct heat range plug for your car??

[Bobby-H]

Those compression test results are definately suspect. To get results that high you would have to have almost 20:1 compression, this would not work, you would get a lot of pinking if the engine would even run at all.

You should get a reading of about 160 PSI ish, it all depends on the atmospheric conditions and how high above sea level you are etc etc. Maybe you should check your gauge is working properly :bookworm: