Quote:
Originally Posted by Chas H
I doubt it has that much effect, but it has some. When the engine is making power things are happening a whole faster than when you do a compression test. Usually if the engine starts easily and idles on all cylinders the compression isn't that bad.
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Cranking speed and inlet restriction have a large effect on compression measurements. So does engine temperature, and I'd think ambient temperature would have some effect as well. Did you do the test on as hot an engine as possible, all plugs removed, throttle held wide open throughout? I've also seen compression gauges with small leaks around the spark plug seal, it can lead to a large error.