Quote:
Originally Posted by Patrick
1004.9/550 (ft-lbs/sec in 1 HP) = 1.83 HP.
So the "vacuum horsepower" is only 1.83.
|
Wow, I was in the shower and missed this thread. What you left out is that air is compressible and that changes the work done pumping air through a throttle.
The actual formula for throttling power is:
HP = D * RPM * Pm * (k / k - 1) / (12 * 2) * ((Pa / Pm) ^ (k - 1 / k) - 1) * (1 / 33000)
Where D is displacement in cu in.
Pa is 1 atm, 14.7 psi.
Pm is the manifold pressure
k is 1.41 for air (adiabatic index or ratio of specific heats)
divide by 12 to change inches to feet, divide by 2 because 4 stroke, and 1 HP = 33,000 ft-lbs/minute
Using this example (114.3 cid, 2042 rpm, 6.2 psi map) the result is 1.8 hp, which shows your (Patrick) formula was good enough, and this post was superfluous.
-mort