Compression test over the weekend...

[///M3Turbo]

I did a compression test on my 97 M3 with 99,600+ miles on the odometer and this is what I have down.

Cylinder1: 201 psi
Cylinder2: 200 psi
Cylinder3: 205 psi
Cylinder4: 200 psi
Cylinder5: 205 psi
Cylinder6: 203 psi

I know they are all within 5 psi of each other and that is what I should go off of, but what is the normal compression pressure that BMW recommends for each cylinder?

[ChipM]

Looks great. Pressures are normally in the 170 to 180 range; the 200s isn't bad and could be due to carbon buildup in the cylinder, or simply an inaccurate gauge.

[vjlax18]

170-180 is when the engine is cold...

And as long as they are all with in a certain range, you are fine. Gauges vary a ton.

[///M3Turbo]

Thanks for the replies. I know it's good as long as the cylinders are all within range of each other.

[danp412]

I as well did a compression check this weekend when I replaced my Spark Plugs. First Cylinder was 225 and the rest were around 210-215. I also found A LOT of oil in 2 of the spark plug shafts so I think that means I need to replace my valve cover gasket. Did you lower your compression at all when you got the Blower put on your car??

[///M3Turbo]

I as well did a compression check this weekend when I replaced my Spark Plugs. First Cylinder was 225 and the rest were around 210-215. I also found A LOT of oil in 2 of the spark plug shafts so I think that means I need to replace my valve cover gasket. Did you lower your compression at all when you got the Blower put on your car??

Stock internals and stock compression on the motor. I'll probably lower the compression if I decide to go turbo over the winter.

[danp412]

Looks great. Pressures are normally in the 170 to 180 range; the 200s isn't bad and could be due to carbon buildup in the cylinder, or simply an inaccurate gauge.

I thought that higher compression readings ment a better/healthier engine. You made it seem like higher than 200 is not good.....??

[northeaste36]

I thought that higher compression readings ment a better/healthier engine. You made it seem like higher than 200 is not good.....??

Up to a point. If there is more pressure than the motor should have with perfect sealing, something is taking up space,be it oil,carbon,etc. Or else the CR has been changed.

[ex wrx]

sorry for being off topic, how do you like your dinan set up? very interested but skeptical :/

[///M3Turbo]

sorry for being off topic, how do you like your dinan set up? very interested but skeptical :/

I like the Dinan SC kit and it's been reliable to me since I'm only running 6 psi, but I just want to go the turbo route in the near future.

[Perculator00]

are there any good DIY for the compression testing?

I cant seem to find it in my bentley

[///M3Turbo]

are there any good DIY for the compression testing?

I cant seem to find it in my bentley

E36 Bentley manual ---- section 100-6 :D

[Perculator00]

E36 Bentley manual ---- section 100-6 :D

good looks

[Perculator00]

Can anyone speculate on the type of compressor tool they use....I went to the auto parts store and they had 3 different types....well...the one for 65 bucks! has all these different adapters and o-rings....I dont think I need

what size does the connection piece at the end of the line(hose) need to be?

I ended up buying the one for 23 bucks....comes with nothing but a guage and a hose attatched to it...

id like to see if I could get one from Sears...craftsman perhaps...\

what yall say?

[Perculator00]

Okay....here are my results

4 ignition turnovers

Cylinders

1......180
2......178
3......170
4.......190(I think I held the key for too long on this one)
5......180
6.......187

motor was fairly cold...just turn it on for 3 minutes

[Def]

Proper procedure on a comp test is to idle/run the engine for at least 5-10 mins to get the piston temp up, then take all plugs out, hold the throttle open and crank it until you really don't get more pressure built-up(typically 4-6 cranks depending on the car).

Make sure your injectors and coilpacks aren't going to fire while you're cranking the car.

[Perculator00]

Proper procedure on a comp test is to idle/run the engine for at least 5-10 mins to get the piston temp up, then take all plugs out, hold the throttle open and crank it until you really don't get more pressure built-up(typically 4-6 cranks depending on the car).

Make sure your injectors and coilpacks aren't going to fire while you're cranking the car.

according to the bentley...warm vehicle....take out the two relays...(main engine relay and fuel...the two square lookin ones in the fuse box)....then remove all coils and proceed on....

I just stuck with 4 cranks....

my question is this....I read in a DIY that he/she only removed the fuse#18 (fuel injection I think) and ran the car until it died..then perform test.......said nothing about removing the two relays....