View Full Version : compresion and Vac

02-12-2004, 04:36 AM
I have a e30 with a 93 325is m50 motor swap ( car that motor came out of had only 96,000 kms ) and am just doing some research. When i put the motor in two years ago i did a compression test and found this:

1 = 185 psi
2 = 185 psi
3 = 190 psi
4 = 190 psi
5 = 180 psi
6 = 185 psi

now.. what should the psi be for a motor in good shape. The Bentley does not say it just says more then 145 psi and no more then 7 psi between cylinders (sp).

Also i have changed out the cams for 95 m3 cams and have a bored out throttle body. I also installed headers and a custom exhaust. I want to do another compression test to see how the motor is doing. Will these above mentioned things affect my compression +/- . I have only put about 10,000 kms on the motor since install but theses have been hard kms with dyno runs and track days and many 1/4 mile runs. And lots of spirited driving.

I would also like to do a vacuum test on the motor to make sure that i don’t have any vacuum leaks. What should i be reading for vacuum off the intake at idle . Any help on this would be great guys.

02-12-2004, 05:32 AM
i had just over 200 psi in each cylinder after my rebuild.. so maybe that gives you and idea. my my compression is 10.5-1 by the book

02-13-2004, 06:21 AM
bump... come on guys... lets hear your thoughts

02-14-2004, 12:15 AM
What about Vacume.... what should it be at idle ?