what are good compression number for 944

dreamer944 · 04-21-2008, 05:49 PM

Hi i still have problems to pass my smog test basic high hc numbers 200 need pass with 150 hc

dreamer944 · 04-21-2008, 05:51 PM

sorry I didn't finish I have to buy new o2 sensor, and see if that help I have new cat new oil, new platium 2 plugs, I did check compression today I got 175psi in all 4 , is that right for a 90k mile engine? thanks waht are perfect number comprssion test in 944 na s

hpservertech · 04-21-2008, 05:54 PM

Numbers look good.

dreamer944 · 04-21-2008, 06:06 PM

forgto also I don't know if make difference my car is euro version ! is that number change form usa versions?

dreamer944 · 04-21-2008, 06:07 PM

forgot I don't know if make difference my car is euro version ! still good number of comprssion test?
is that number change from usa versions? or could be same ! I guess If all cylinders are equeal is good but how high is consider perfect number?

Techno Duck · Techno Duck's Garage

The compression numbers will be higher for a euro car because they had higher compression pistons. Most USA cars ('83-87) had 9.5:1 while all euro cars had 10.6:1 compression. Im not sure what your values should be at, but at sea level for a USA car i generally see 150-170 being the norm. There are alot of factors to take into account like how warm the engine is and obviously your altitude. As long as all of the #'s are within 5-10% of each other your in good shape. A leak down test would tell alot more.

Anyhow high hydrocarbon levels mean your running rich. Your on the right track with replacing the O2 sensor. Another commonly overlooked cause is the DME temp sensor which is located underneath the j-boot. It is a blue topped connector. This sensor tells the DME to run in open loop for warmup (defaults to rich condition). When the coolant reaches a certain temp, it will signal the DME to enter closed loop. When the sensor goes bad, it never signals the DME to enter closed loop.

And are you sure your euro car even has a O2 sensor? They did not come with them originally.

dreamer944 · 04-21-2008, 07:09 PM

Thanks weel all number and cylinders were same 172-170 , I will do leak down test my car doesn't burn oil or has starting issues , the temp sensor you said was bought new 1k ago when i have full reseal engine new rings, and tune, but as i said I have web cam racing I not sure is that in fact causing the level of hc so high, , but for same reason i install msd ignition system to get better burn of gas ! I already try all possible ways to get down the hc, even pay mechanic to adjust the afm but he said he adjusted to minimum, I'm not sure , he did check the o2 sensor he said looks new he got me number of 272mvolts to 285 mvoltz is running I'not sure what that means!