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Compresion Pressure.
Posted: Wed Nov 25, 2009 8:29 pm
by Ambidextarous
What is the correct cylinder compression pressure for the Perkins engine. One of my cylinders is well below the other two. Also, if there's trouble with one, is there likely to be trouble with the other two?
Posted: Thu Nov 26, 2009 7:39 am
by JC
I don't know for sure what the compression pressure is, but here's my best guess. The compression ratio is 16.5 to 1. Atmospheric pressure at sea level is 14.7 psi. 16.5x14.7= 242.55. Subtract 14.7 for the atmospheric pressure and you have 227.85 psi. Even a new engine is not 100 percent efficient, so it should be a little less than that.
Anyone else want to guess?
Posted: Thu Nov 26, 2009 8:27 pm
by Ambidextarous
Thanks JC, i've tried looking on the web but have found nothing so far. I thought it worth posting on the forum but i'll keep looking.
Cylinder Pressure.
Posted: Thu Nov 26, 2009 9:33 pm
by Bensdexta
Ambidextarous wrote:One of my cylinders is well below the other two. Also, if there's trouble with one, is there likely to be trouble with the other two?
I read that a pressure difference between cylinders of more than 10% is indicative of a problem.
As to the actual cylinder pressure values, it seems to be quite a complicated subject because the compression is approx adiabatic (ie no loss in heat) so the air heats up, which increases the pressure, but it also depends on valve timing etc. So JC's worthy effort above may be a bit out! Unfortunately I can't suggest a better value so maybe the difference between cylinders is the most reliable indicator
All the best,