Compression Test Results::

[m3f_resisTm3]

Before i order/ install a supercharger, i wanted to have a mechanic run compression tests on my engine, since it is running fairly high miles.



Here are the results:



1-140

2-130

3-130

4-130

5-125

6-130



The mechanic did not know normal bmw #'s, so i was wondering if these PSi readings were good?



They seem pretty consistent, but just curious to what it should be at.



Also, safe to go FI w/ these numbers? ( AA S/C )





Brett.

[m3f_96M3Power_4547fc3d60]

mine were 180-190... I heard that those numbers were normal, but I'm not sure.

[m3f_beemertek]

Bmw spec is 10-11 Bar (1 bar=14.7psi@ sea level)

[m3f_Sirius_880bd69485]

So, 141-161.70 is good...

[m3f_PurpleM3Pursuit]

im glad sirius is here.. he can clear it all up.. lol

[m3f_Sirius_880bd69485]

Lol.. simple math... :chair:



As long as I did it right, it looks like its somewhat below par.

[m3f_mighty-dog_11395d17be]

10-11 bar x (14.7 psi / bar) = 147-161.7 psi.



I'm an engineer so I'm used to more difficult calculations!

[m3f_Sirius_880bd69485]

Didn't I say that before? :chair:

[m3f_Drifter_23d8df4bc6]

Ask AA, they have a pretty hard test before they work on cars.

[m3f_DoctorBentValve]

Your compression is fine. Spec is 142-156 psi.

[m3f_astan100_7ef66fbe89]

Sirius...put that beaten' chair away.

[m3f_Sirius_880bd69485]

Must be perfect! Not one cylindar meets min specs... :chair:



Your engine is blown.. time for a new one.

[m3f_beemertek]

Blown is a little harsh. Keep in mind that two people can do a compression test and get complete different results. I've seen guys count strokes and only turn the engine over a few times. When I do a compression test I let the guage go until it stops building pressure. Another factor is that 1 bar=atmospheric pressure. 14.7 is at sea level. I would have someone do a leakdown test on it. If you have low compression the combustion pressure is gong somewhere. A leakdown test is your next step. BMW says that 15% leakdown is acceptable.

[m3f_Sirius_880bd69485]

Heheh. I was being scarcastic.



He is in Pa, so parts of that are close to sea level.

[m3f_beemertek]

So his engine really is weak or his mechanic didn't know what he was doing.