My Compression Test Results...with a flaw.

[BadAss95-530i]

Bizzare i signed on today to see that e34.535i.sport just posted this very question when I just did this test yesterday. I didnt wanna pirate his thread though with my results. Please fellas, chime in. I Grabbed a $25 comp test guage from advanced auto

1.i warmed the engine
2. i pulled the plugs
3. disconnected my dme and fuel relays
4. screwed on hose
5. cranked with throttle at full wide approx 5 rotations
6. noted where it started to even out when i bumped the starter for a roughly 4-6 reps
7. repeated with a little oil in each for the 'wet' test

*My variable/flaw. It was a bit cool out and i wasnt exactly swift with getting the deal done. I am willing to bet that the engine was no longer warm by the time i got everything pulled and cranked. How bad is this? Would a cold engine mean my results are worthless or appear better/worse than my readings indicated?

Results
Dry
Front bumper
5-198 1-205
6-180 2-195
7-175 3-198
8-185 4-188


Wet
Front bumper
5-205 1-218
6-183 2-205
7-185 3-225
8-192 4-200

So, im nervous about the coldish engine first of all, and the (as high as) 25psi difference in wet to dry makes me worry as well. IIRC someone said I should mark the very first reading (which for all was around 130, but it spiked up, slouched down, then spiked well above that on the 2nd rotation so fast i could not possibly record it.) I am planning on going ahead and leakdown testing it next regardless. But i am curious to hear some speculation as to the state of my Nik engine.

Thanks guys
Terran

[e34.535i.sport]

Hey there, could I just ask quick question - When you took the sparks out with the engine hot did you encounter any problems? Only because I'm going to do it myself tomorrow but I'm dubious about pulling the sparks out with the engine hot incase I damage the threads on the head...

[Tiger]

The right way to do the test is when engine is cold or warm. Take all plugs out... no need for any throttle... just crank. You should pull out the fuel pump relay... or best is use a remote starter so your DME and fuel injection is off

The right reading from the tester is the third jump and stop. Do not crank for more than 20 seconds at a time without 5 minutes cooldown. Set the gauge to face you when you sit in the car... so you can stop cranking after the third jump.

[BadAss95-530i]

Hey there, could I just ask quick question - When you took the sparks out with the engine hot did you encounter any problems? Only because I'm going to do it myself tomorrow but I'm dubious about pulling the sparks out with the engine hot incase I damage the threads on the head...

In the last few months Ive had the plugs out 3 times in various states of temp. I encountered no problems even at their hottest. hope this is helpful.


I did the full throttle cuz Bill R. mentioned it specifically in another guys post.

http://www.bimmer.info/forum/showthread.php?t=13429&page=3&highlight=dry+compression+test+disable

The bently also said "with accelerator pressed to the floor, crank engine..."



So Tiger, you think i should do it again? Cuz i am leaning toward agreeing with you. 3 pumps would make more sense to me than just letting it run till it tops off. But again, I went by the bentley it said "Record the highest value indicated by the guage" in section 100-6.

At this point im committed to the leakdown anyways though. So i guess we shall see...

[Tiger]

Leakdown test is far more accurate... although it takes more time to do. With your readings, I am not concerned with your engine condition.... it is good.

[632 Regal]

3 cranks is normal, peddle to floor shuts the fuel off.

[Dave M]

The issue is torquing a plug into a hot head. Greater chance of stripping threads. Remove em whenever you want, just watch when you put them back in.

Tiger, why is 3 cranks is the 'proper' way to test compression. I've not heard this before. On many occasions, depending on the vehicle and the tester, I would not have gained a stable, max comp by three cranks. I'd have a difficult time interpreting results in these circumstances.

Also, I've also been under the impression (from others here and Bentley) that the throttle should be wide open. Can you enlighten me as to why it should be closed.

Dave