The short answer is yes, the long answer is no... if you are checking cylinder pressure of an engine
. Stop reading here, if you aren't working on an engine
... (Grin... Its late and I won't sleep till its all out on paper.)
Engines have two compression
ratios. Static, and dynamic.
Static, is swept area, the stroke of the connecting rod by the cylinder diameter (Which gives your base volume) over combustion chamber volume. This accounts for head gasket
thickness, valve cutouts, and depth
of the top ring land. Pretty straight forward.
Dynamic involves the overlap of the intake and exhaust
valves. Because there is an overlap, some intake charge exits with the exhaust
. The idea being that at high rpm's the exhaust gas does not have enough time to exit the chamber completely. Engines with less overlap are geared towards low rpm
usage... and develop a lot of cylinder pressure, but still less than the static ratio. Engines meant for high rpm
use develop less compression, but have better cylinder filling... less exhaust in the chamber.
Once you have the static compression ratio, you take the camshaft profile and calculate the dynamic compression.
But... if you were to check the cylinder pressure you still have a few kinks. That is leakage. The piston rings do not seal absolutely, and the valves may or may not seal perfectly. So... if you know the PSI of the cylinder, you can't necessarily reverse engineer
the puzzle unless you know static or dynamic... and guesstimate the engine wear.
Finally getting to your question:
You take your atmospheric pressure in PSI, sea level 14.7. Then you multiply your by the number above the denominator. In your case 10. You end up with 147psi. This assumes a perfect seal at sea level... engines don't. The seals
with flippers on the other hand...
Because of all the other factors, it isn't very reliable beyond a ball park figure. So... for the sake of adding to the ball park figures: A gasoline powered engine meant for low rpm use will have a range between 115-150psi. 100psi is the wear limit on the low side, less than that and no tuneup will cure what ails her. A wild machine will range from 150-250psi. Something thats routine maintenance
involves removing the cylinder head
may start reaching for 275psi... and push the limits of what race
octane gasoline can handle.
Detonation is the reason behind all this. Increasing the cylinder pressure improves the thermal efficiency of the engine, but only increases brake output by about 2-4% a point. Low maintenance
machines sacrifice potential in name of longevity. Detonation is the reason. Gasoline detonates at 1075 absolute... or 615F. This benchmark is a theoretical engine with 13:1 compression at sea level on a 90 degree day. (F to absolute = +460) Raising the compression ratio from 10 to 11 raises the cylinder pressure 147 to 161psi. (On paper!)
... and the math which is used to calculate the difference in temperature between the two compressed ratios is eluding my tired brain. Good stopping point!