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+--- Thread: Compression Readings (/showthread.php?tid=3078)
Compression Readings - Greazzer - 11-01-2011
Checking the compression on my tired OM617.952 and the results are as follows:
COLD: Cylinder 1 300 psi, Cylinder 2 300 psi, Cylinder 3 310 psi, Cylinder 4 280 psi, and Cylinder 5 260 psi. The latter 2 is explainable by the fact that I have a nice oil leak in my head gasket.
WARM (running temps) Cylinder 1 280 psi, 280 psi, and 260 psi. Did not check 4&5.
What's up with that. What is "good" compression? I've seen numbers as high as 440 as "good" on the various forums. The valves were adjusted in Spring 2011 and I have very limited blow-by. Does cold vs. warm have any impact ?
RE: Compression Readings - Captain America - 11-02-2011
I need to check mine! Mr. D*ckface (FI) posted his readings a few times... in his build threads
RE: Compression Readings - Greazzer - 11-02-2011
The FSM puts the readings at 22-24 Bar, so 22 - 24 x 14.503 = 319 psi - 348 psi. BUT, my readings went down from a cold engine to a warm engine. My temps never get to 80 C -- too good of a radiator now -- LOL. The FSM says 80 C and 8 revolutions to get the reading. I was wondering why it went down as the engine was warmed up -- about 50 C when I checked it. This is for the OM 617.9XX engine. The 4 cylinder version has much higher PSI.
Thanks,
RE: Compression Readings - ronnie - 11-03-2011
normally they should be more when warm, about 50 psi. I don't really have an answer. Mine range from 300-350psi measured cold. 616 engine.
RE: Compression Readings - Volker407 - 11-05-2011
When my temperature never reached 80C (everything stock) the thermostat was broken.
Gruß
Volker
RE: Compression Readings - Greazzer - 11-06-2011
After I replaced my radiator with a Be Cool 3" all aluminum radiator, my car never hits 80C again. One of the best modifications / upgrades I have done and under $200.00 All aluminum radiator is FAR BETTER than the OEM Behr.
RE: Compression Readings - plurkje - 11-08-2011
(11-06-2011, 09:25 AM)Greazzer After I replaced my radiator with a Be Cool 3" all aluminum radiator, my car never hits 80C again.
Even with a swimming pool of cooling fluid, your car should reach 80C in a short driving period. If not, then your thermostat is too weak to close as it should. Due to driving with low engine temperatures the engine loses it's compression much quicker.
The OEM radiator is very capable of cooling an OM617a, I admit; it is made of aluminium.
RE: Compression Readings - Greazzer - 11-08-2011
I had a BEHR which was OEM and the top and bottom were not aluminum. Some sort of plastic. With my former BEHR my car hit 90+ C all the time, every day, especially in the summer. With an ALL Aluminum 3" radiator, which is x2 the thickness of the OEM, my car NEVER hit 80C. So, same exact situation in all regards except different radiator and my car does not reach 80C. With the OEM, well over 90+, so I cannot see how the thermostat would be "working" with a BEHR radiator and somehow it knows not to work with a 3" aluminum radiator. However, that is not the purpose of my thread.
I wanted to know why the compression readings went DOWN when the engine warmed up, although it did not hit 80C per the FSM. Any ideas ?
RE: Compression Readings - DeliveryValve - 11-08-2011
I agree you should be getting about 50 psi greater when warm than cold.
Are you using a Harbor Freight compression tester?
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RE: Compression Readings - Greazzer - 11-09-2011
Of course I am using a Harbor Freight junk line tool. LOL ..... do you think that could be it ?
RE: Compression Readings - iheartboost - 11-09-2011
The harbor freight tester has been shown to not be the most reliable thing.
RE: Compression Readings - DeliveryValve - 11-11-2011
(11-09-2011, 05:54 AM)Greazzer Of course I am using a Harbor Freight junk line tool. LOL ..... do you think that could be it ?
Yes I think it is. I have found they are reliable on one Round of use, then you throw it away.
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