COMPRESSION TESTING

I live at an elevation of 5000 feet. I think the compression reading
to be expected should be corrected from the manual value, for the
reduced air density at this location. Does anyone know the proper way
to make this correction?

John

 

Ooooh, I like this thread already. Methinks it has great potential.

So if you have a reading of 160psi at sea level at (say) 70 degrees F,
what would you expect at 5000 feet?

 

<snip>

*Impressed*

 

You did not read my message, or at least, it did not sink in. I asked
whether anyone KNOWS the PROPER way to correct for density.

 

http://dbhs.wvusd.k12.ca.us/GasLaw/KMT-Gas-Laws.html

It's got something to do with avocados, iirc.

 

All this gas law stuff looks quite familiar, but I'm not sure it is the
answer here.

Could be you don't have to correct for anything (but this needs more tech
input to analyze correctly.) For one thing the gauge is measuring gauge
pressure, not absolute pressure.

I think the important thing is that all the cyl's read close to each other,
like, within about 5%. And if they are different, it could be something like
a valve clearance adjustment. It doesn't mean you have fried valves, or
something worse, if they aren't all the same.

Dave "not really answering the origonal q but thinking he's contributing
something worthwhile" W.

 

Ok, so are you "Pete" or "Dave"?

From the perspective of my feeble experience, I agree with Petey-Dave.

My manual ('83 Kawa KZ440) actually states that exact cylinder pressure, as long as it's not well below the suggested range is not as important as cylinders having matched pressure AND (here comes my contribution)...

the pressure of the cylinder should be taken, then add a tablespoon of oil to the cylinder and recheck the pressure. If the pressure WITH oil is considerably higher (subjective terms, I know) then you likely have a piston ring job in your future.

Careening farther from john's original question but also hoping to add something.

Your mileage may vary.
-Paul