Compression Test results

e92Nathanson · 11-20-2023, 10:03 PM

How screwed am I? 2008 N54 335i coupe. 120k miles
Cyl 1: 154
Cyl 2: 151
Cyl 3: 158
Cyl 4: 152
Cyl 5: 155
Cyl 6: 135

phils2 · 11-28-2023, 03:55 AM

Not that bad. Can you do a cylinder leakage test to hear where it's going?

marvinstockman · 11-29-2023, 07:33 AM

You're perfectly fine. Have you asked Google for compression numbers?

What problem are you trying to solve?

CLEAN13BOOSTED · 11-30-2023, 08:32 PM

Agreed, what's the concern? #6 stands out but relative to the others there's not a huge variance.

lobotomy · 12-01-2023, 04:36 PM

By normal acceptable industry standards, there should not be more than a 10% drop from the highest (#3cyl), and your lowest (#6cyl). That means your allowable max is a 15.8 difference between #3 & #6. Your test results show a difference between those two cylinders is 23, so yes, #6 is subpar and the difference is over acceptable allowance.
That being said, I agree with all the above replies. Is there a performance or running issue? Are the results from a wet or dry test? If you have an issue, phils2 (post #2 above) recommendation to do a leakdown test on #6 cyl. would be a good place to start. You failed to mention how many miles you have on this engine. While #6 is subpar compared to the others, how is the engine performing otherwise?

phils2 · 12-12-2023, 04:36 AM

Surely it's not still in bits?

11-20-2023, 10:03 PM	#1
e92Nathanson New Member 4 Rep 21 Posts Drives: 2008 BMW 335i Coupe Join Date: Apr 2021 Location: Baltimore, Maryland iTrader: (0) Garage List 2008 BMW 335i [0.00]	How screwed am I? 2008 N54 335i coupe. 120k miles Cyl 1: 154 Cyl 2: 151 Cyl 3: 158 Cyl 4: 152 Cyl 5: 155 Cyl 6: 135
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11-30-2023, 08:32 PM	#4
CLEAN13BOOSTED Private First Class 74 Rep 104 Posts Drives: 2013 BMW E93 3351 Join Date: Oct 2023 Location: FLORIDA iTrader: (0)	Agreed, what's the concern? #6 stands out but relative to the others there's not a huge variance.
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12-01-2023, 04:36 PM	#5
lobotomy Private 26 Rep 69 Posts Drives: 2011 328xi Join Date: Aug 2010 Location: NY iTrader: (0)	By normal acceptable industry standards, there should not be more than a 10% drop from the highest (#3cyl), and your lowest (#6cyl). That means your allowable max is a 15.8 difference between #3 & #6. Your test results show a difference between those two cylinders is 23, so yes, #6 is subpar and the difference is over acceptable allowance. That being said, I agree with all the above replies. Is there a performance or running issue? Are the results from a wet or dry test? If you have an issue, phils2 (post #2 above) recommendation to do a leakdown test on #6 cyl. would be a good place to start. You failed to mention how many miles you have on this engine. While #6 is subpar compared to the others, how is the engine performing otherwise?
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11-28-2023, 03:55 AM	#2
phils2 Private 5 Rep 54 Posts Drives: 318 D Msport Join Date: Oct 2019 Location: uk iTrader: (0)	Not that bad. Can you do a cylinder leakage test to hear where it's going?
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11-29-2023, 07:33 AM	#3
marvinstockman Major 399 Rep 1,080 Posts Drives: 2011 BMW 328i Join Date: Aug 2015 Location: Rockville, MD iTrader: (0)	You're perfectly fine. Have you asked Google for compression numbers? What problem are you trying to solve?
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12-12-2023, 04:36 AM	#6
phils2 Private 5 Rep 54 Posts Drives: 318 D Msport Join Date: Oct 2019 Location: uk iTrader: (0)	Surely it's not still in bits?
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