m30 compression test???

[Robotin]

when doing a compression on a 535i (e28) what should a good compression be???

[slammin.e28]

190+/- 10% across the board should do ya. Whaddya have?

[Robotin]

100 and 105 peak..... what does this mean???

anything i can do??

[LJ851]

Do a leakdown test. Are all the cylinders close to the same compression #'s?
If the engine leakdowns well, cam timing is about the only thing that can bring down all your compression #'s equally.

[slammin.e28]

Do a leakdown test. Are all the cylinders close to the same compression #'s?
If the engine leakdowns well, cam timing is about the only thing that can bring down all your compression #'s equally.

This.

Also, did you hold the throttle open while doing the comp test? This will effect results. Usually if they are all about the same, it's a good sign, unless they are all abnormally low. I think mine were ~170-180 on my parts car before I tore the engine down for HG. (Two cyls were ~50-60). It ran great once I put the new,m uncracked, head on it.

Leak down test is better anyways, and can tell you what is wrong, instead of something is wrong.

[LJ851]

This.

Also, did you hold the throttle open while doing the comp test? This will effect results.

Thank you slambotron, i forgot to mention that!

[slammin.e28]

Thank you slambotron, i forgot to mention that!

I try to be the e28 master, I really do, lol.

[catuned]

Also doing a compression check make sure your battery is charged rely good.
Or have a battery charger on it.
You don't want to mistake for low compression because the engine is barely turning over.

:)

[ross1]

If compression is even on all cylinders then your low numbers could be explained by method or cranking speed. Throttle wide open and be sure battery remains charged as slow cranking will effect results. Also watch how the needle rises with each compression stroke, a healthy engine will get most of the way there on the first stroke. The final reading is typically taken after three strokes.
A leakdown test will tell you more.
If the engine ran well and compression is even I'd not sweat the #s.