I did a compression check on an engine I built years ago.. I cant find the paperwork or build info for this engine... so anyway
All six cylinders are 175 psi!!! I like
is that really 12:1 compression? I did another compression check.. and came up with the same results 175 psi
bored today?
Leave it forgotten--it doesn't work.
The relationship of compression pressure to compression ratio is a complex one, and rather non-linear. Things like the state of charge of the battery, the electrical losses to and from the starter, friction losses inside the engine, and so on add up. So do things like the cam selection--a milder cam will keep more of the pressure "inside" the chamber than a wilder one with lots of overlap. Finally, the pressure-to-volume relationship is not a constant one--what's inside the chamber is very much not an "ideal gas", so you cannot use the Ideal Gas Law on it.
A tight stock 2.0 motor can easily make 150 PSI compression. That does not mean it has 10.3:1 compression...
--DD
Now this is a funny anecdote:
Our GT3RS lost power in one cylinder a few weeks ago.... so we did some forensics
turns out the GT3RS is making 175 psi when we check compression, also our RS just had a bad injector...interesting it has 175 psi on a cold cranking compression test
I know the compression ratio of the RS....built by Porsche Motorsports.. then refined by a rebuild from Peter Dawe.
175 PSI is normal for EVERY engine I have ever built...
Then again... My gauge has been stuck on 175 for 40 years.
So all my engines have great compression....!!!!
On another note. I think DD said it best....
And unless you know exactly what cam you have and what the leakdown numbers are on a HOT engine. All it tells ya is that you probably have good rings and a solid valve/seat interface.
What are the compression numbers for each individual cylinder?
Regards,
Clayton
here is an example....
a 2L 906 motor, may only have 40 psi of compression..... on a test. but it makes 230 hp....
cams make a huge difference....
john rogers had a nice reply to this question once.
Them thar numbers probably mean...... Good things...
Keep dem fingers crossed and fire the bitch up...!!!
Good luck Tim..!!!!
Clayton
adiabats..... worst section of physics LOL
heat engines etc....
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