Thread: S54 Swap
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Old 12-16-2012, 05:44 PM
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dc_wright dc_wright is offline
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Mein Auto: '06 Z4 3.0si, '11 128CiC
Originally Posted by JayMac View Post
Okay just finished the compression test of the current engine. Pleasantly surprised. I have read the following info and do not know if it is true or not but if so I am even more please.
1. More aggressive cam will lead to lower numbers, I have M3 cams in here.
2. Minimum E36 should be 142-156? I got 190 to 200 across all 6 cylinders.
3. You want the numbers to be within 85% and there is a conversion chart for altitude on Pelican parts. I am right on the water so probably less than 100 ft.
Hope all this helps to sell this when the time comes.
Cylinders in order, 195, 190, 190, 195, 195, 200

Now back to pulling some crap apart
Nominal should be atmospheric pressure x compression ratio which would be 14.7 psi x 10.5 = 154 psi. Higher readings are typically caused by carbon build up and/or unburned fuel injected into the cylinders. You've got consistent readings across all 6 and they're all higher than the nominal so you're good!
An aggressive cam depressing the readings is a myth. The compression gauge captures the peak pressure and the only way a cam could affect that was if the valves never closed.
2006 Z4 3.0si Sport Package (But I'll still hang with my "homies" in the E36 forum)
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