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Discussion Starter #1 (Edited)
I had BMW Towson do a compression and leakdown test on my M5. Here are the results:

Miles on engine: 39,800
Oil Type: Castrol TWS 10W/60

Cylinder RMS Compression Pressure Leakdown
1 195 psi 0%
2 195 psi 0%
3 196 psi 0%
4 201 psi 1%
5 200 psi 0%
6 200 psi 0%
7 198 psi 1%
8 199 psi 0%

BMW S62 spec on RMS Compression pressure is 175 psi to 205 psi.
BMW S62 spec on leakdown is 0% to 9%.

I'm kinda floored by the leakdown test. But, the tech said he did it twice and the numbers were consistent.

Regarding compression, the test system measures the RMS value of the cylinder pressure, so the peak pressures in the above range from 275 psi to 284 psi. In a previous thread I had predicted about 300 psi for peak pressure, so in that calculation my estimate of pressure loss in the inlet air system was too low.

Jeff :cheers:
 

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Discussion Starter #3
RRoberts said:
Or the assumed value of volumetric efficiency was too high.

Regards, Dick Roberts
I think we're talking the same thing Dick, but using different languages. I'm referring to flow loss through the inlet system that then manifests itself as below atmospheric pressure when the cylinder fills.

What do you think about the leakdown numbers? Jeff
 

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x703jko said:
I think we're talking the same thing Dick, but using different languages. I'm referring to flow loss through the inlet system that then manifests itself as below atmospheric pressure when the cylinder fills.

What do you think about the leakdown numbers? Jeff
They look pretty good to me, at the low end of the factory acceptable range. I would not be concerned at the difference between 0 and 1%, especially as the two cylinders do not have the lowest compression figures. Plus all the compression figures are close. I assume this engine does not use much oil?

Regards, Dick Roberts
 

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Discussion Starter #5
RRoberts said:
They look pretty good to me, at the low end of the factory acceptable range. I would not be concerned at the difference between 0 and 1%, especially as the two cylinders do not have the lowest compression figures. Plus all the compression figures are close. I assume this engine does not use much oil?

Regards, Dick Roberts
For a while, I had a problem with a leaky oil filler cap (as some others reported). Once I solved that it's settled down to about a qt every 2000 miles.

Jeff :cheers:
 
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