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2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
XENTRY Compression Test
XENTRY allows you to perform a "compression test" which measures the speed of a cylinder during a fuel-less start cycle and compares the difference between the slowest and fastest cylinders. I performed this test on my two cars, a 2014 C350 (M276 3.5L NA engine) and a 2015 SL400 (M276 3.0L Bi-turbo engine). The comparative results show the engines to have good relative compression. Not sure what the threshold is between healthy and sick engines.
PFL205.064 with M276.823 (Oil pump solenoid defeated)
Originally Posted by JettaRed
XENTRY allows you to perform a "compression test" which measures the speed of a cylinder during a fuel-less start cycle and compares the difference between the slowest and fastest cylinders. I performed this test on my two cars, a 2014 C350 (M276 3.5L NA engine) and a 2015 SL400 (M276 3.0L Bi-turbo engine). The comparative results show the engines to have good relative compression. Not sure what the threshold is between healthy and sick engines.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
New Compression Test after changing my oil to Pennzoil Platinum Euro 5W-40. Interesting results. There is now about a 15% increase in rpm speed. I did capture oil, coolant, and transmission temps this time (see note in image). Ambient temperature is 78°F. Not sure how to interpret a faster spinning engine. Certainly there is less resistance to compression that the starter has to overcome. I know my battery voltage was 14.4V this time and with a battery charger attached. I do not know the voltage of the previous test, but I did have the battery charger attached then, as well. Master Investigator @S-Prihadi and Master Analyst @CaliBenzDriver , any ideas?
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
There could be multiple differences between the conditions the two were tested at. And initially and intuitively, we would say slower speed means better compression, but I'm not sure of that. Faster speed means less resistance, either due to friction or greater pressure (or both). I would like to think it is due to less friction. The Pennzoil Platinum Euro is more than just another 5W-40.
I have another oil change coming up for my C350, which had similar result to my earlier SL400 tests. I'm not sure now if I want to go with the Pennzoil or the Motul Molygen I was going to use. If I use the Pennzoil, I can then compare with the SL400 to see if there are similar results.
04-12-2024, 11:14 AM
