PDA

View Full Version : 325e compression


SamE30e
08-14-2007, 09:31 PM
I did a compression test on my car today not knowing what the spec is. I got these all while cold.

#1 - 170
#2 - 167
#3 - 166
#4 - 166
#5 - 166
#6 - 170

What is factory spec? My online manual didn't say anything. It just said pull half the engine apart. All I did was unplug the maf, pull the intake boot off, pull the fuel pump fuses, and all the plug wire then test each individual plug.

e30_kid89
08-14-2007, 10:10 PM
you shoulda done compression numbers when its hot those numbers are what counts.

SamE30e
08-14-2007, 11:03 PM
Yea I guess so, but they numbers can't really go down when it get hot.

everlast
08-14-2007, 11:37 PM
That seems a little high; it should be 155 if I'm not mistaken, plus or minus 10% (likely to account for gauge variance.) You held the throttle open while cranking too, right?

I think high compression can mean carbon build up; try running some STP or something through it maybe... perhaps other peeps know more about this?

Wannabe
08-15-2007, 02:42 PM
why should the throttle be held open while doing this?

everlast
08-15-2007, 02:47 PM
It allows as much air into the cylinder as possible. My instructions on the compression testing kit I have agree.