Hey I just ran a compression test on my s50. My lowest cylinder was number 6 at around 135. 1-5 were all 140-145. I got these numbers on two tests. I'm happy to see the numbers are fairly consistent but over all is this low-ish compression on an s50 with 115k?
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Very very low, especially at your elevation (276ft based on your location).
Get a new tester of quality and try the test again. Make sure you are connected to a strong battery charger, the motor is warm, that you are holding the throttle WIDE OPEN during the test, and that you are cranking till the numbers peak (usually 12-16 cranks).
Last edited by Braymond141; 09-16-2018 at 03:20 PM.
Hmm. I bought the highest rated tester on Amazon. Car was at operating temperature and I had throttle wide open. My buddy said I was peaking at about 4 cranks. Each cylinder I gave it about 8 cranks
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I’ve never seen any of these motors peak at 4 cranks unless using oil for ring diagnostics. I still suspect the tester.
OP, did you pull the fuel relay? If not, fuel will wash the walls and throw off the readings significantly.
04M3 TiAg 69k slick-top 3 pedal
99M3 Cosmos 61k S50B32 euro 6Spd
88M3 AW 43k miles Project FS
WTB: 3.5" Eurosport/Conforti CAI
stock cams, timed correctly (ie, not too much overlap?) Numbers are low, but consistent, so that's definitely good.
As far as internals go this is a completely stock motor. I have no idea on timing as I've never checked it. Yes I ran it for a good drive and pulled it in. Then I pulled the fuel pump fuse and started pulling the plugs
Last edited by AlpineM3OldAsMe; 09-16-2018 at 04:41 PM.
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