Bob, you are correct 30” Hg (or
29.92”Hg) is standard day sea level ambient pressure and 15 psi is approx
30” Hg. However, normally when you are talking about boost - you the
convention is that you are talking about pressure above ambient air pressure. So 15 Psi Boost = 14.7 psi (ambient)
+ 15 psi(boost) or if you prefer = 29.92 “Hg(ambient) + 30”Hg(boost)
= 59.92” Hg Total absolute pressure in the manifold – so, Ok, shoot
me - I was 0.08” Hg off in my estimate {:>).
Ed
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Bob Darrah
Sent: Friday, January 23, 2009
9:58 PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: HP was :
Mark's BBQ Run / 20B numbers
Hay, Ed, I always thought 15 Psi boost was about only
30" Hg of boost-atmospheric pressure (about 15 Psi) equals only (about )
30" Hg. Where did I go wrong?
----- Original Message -----
Sent: Friday, January
23, 2009 2:10 PM
Subject: [FlyRotary] Re: HP
was : Mark's BBQ Run / 20B numbers
Should be a fire belching dragon of an
engine at over 15psi, Greg.
15 Psi boost would be roughly
60” Hg of boost which at an A/F ratio of 12 (assume you would run it a
bit rich at those boost levels) would give at 6000 rpm approx 550 HP burning 51
gph (more power at high rpm and boost naturally) and producing a
total of 25000 BTU/Min of heat to be dumped through the radiator and oil
cooler. Boy, you will produce more heat energy that gets dumped through
your oil cooler (8484 BTU/Min) than my total (coolant and oil heat) entire
engine puts out. Hope you have big radiators and oil cooler {:>).
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