I have investigated this a bit more and consulted with a friend who is a
powertrain development engineer. Randall, you are absolutely correct about
this. I used 3 squirts of oil from my oil can for the wet compression test.
I measured this last night and it comes to about one teaspoon or 5 cc. The
cylinder volume at TDC is about 61 cc, so 5 cc of oil is significant. Our
preliminary calculations show this can give about a 9% increase in peak
pressure. I saw between 4% and 17%. But I didn't precisely measure the oil,
I just squirted.
I would like to calculate more precisely, but need a couple of bits of data
that do not appear in my shop manual. Does anybody know the intake valve
closing timing and the con rod length for a 72 TR6? If so, I will complete
the calculation and post it.
Thanks,
Hugh Fader
72 TR6
> conditions, caused by the octane-lowering effect of the oil. The
> increase in 'wet' compression is probably caused by the oil taking up
> part of the combustion chamber, in effect temporarily increasing the
> compression ratio. It's unusual for rings to wear that
> I have just completed a compression test on my 72 TR6. The test was
> performed using a screw-in compression gage, with the engine hot, and with
> all plugs removed. Here is the data.
>
> Cylinder/Dry psi/Wet psi/Plug Condition
> 1/100/115/brown, dry
> 2/100/117/brown, dry
> 3/105/115/brown, dry
> 4/105/110/oily, pitted
> 5/107/113/brown, dry
> 6/101/110/brown, some oil
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