>>>What's "true" pressure?<<<
David,
"True" (remember I did say I wasn't sure what it was called) pressure is
the sum total of what Theo and Tim explained. So, basically, yea..., what
they said (better than I could).
To me "True" compression is the cylinder pressure (in PSI) that is the
end result of the cam used. Static compression (the one expressed in a ratio
like 12:1) assumes the valves are closed for the full 180 degrees of the
compression stroke.
The reason I brought the issue up is that you spec-ed a 12:1 ratio
with a stock motor. Given that motors with those ratios (12:1) often have
cams with significantly longer durations the end result could be the same
cylinder pressure (in PSI) as a stock motor with a 9:1 compression ratio.
Thus, a stock motor with 12:1 ratio could have a cylinder pressure that
might be WAY too high. I don't know that for a fact, but it is something
that needs to be considered.
This may not be a perfect analogy, but compression ratio is like the square
footage of a building. And, cylinder pressure is the people you are going to
put into it. However, whether those people are 100 NFL line men of 300 Paris
Hilton's (the cam specs.) does make a significant difference. In this
case there is the "true" occupancy based on who is in the building, not
just it's size.
Now, if I can just figure out what Bob said... .
Tom
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