Barnhart wrote:

Going thru maps tonite.  Turbonetics have maps online now.

A 20bt at 300hp will fuel burn approximately 20 gallons/hour. This would

be 20 x 6 = 120 lbs

fuel/hour and 1440 lbs of air/hour. Total 1560 lbs mass air flow/hour.

26lbs/min.

At 200hp fuel burn is about 10 gallons/hr.  780 lbs/hr mass air flow or

13 lbs/min mass airflow.

Pressure ratio is 14.3 (ambient pressure) + 10 (lbs boost) divided by

14.3 =  1.69  at 1000 ft.

How is the ambient pressure determined for higher altitudes?

Barny
MGDQ

How I wish this were true.  That would be a BSFC of .3 at 200 HP, too good
to be true.
On a nice cool day (like today) at 1000 ft, full throttle and 214 MPH, my
13B will be sucking down 20 GPH at max power mixture.  It goes down to 15
GPH at best economy mixture (but the speed & power goes down a bit).

I figure on loosing about 1" Hg per 1000 ft altitude.  Actual value is a bit
less.  NA engine will be down to around 50% at 18,000 ft which is the target
cruise of my 20B powered RV-8.

Tracy Crook
tcrook@rotaryaviation.com
www.rotaryaviation.com

200 HP at 20 gallons an hour is BSFC of 0.6. 
That is right in the ball park with this air cooled aircraft
engine. Note the BSFC is .550 at 2700 RPM and full throttle. 
At 1700 RPM WOT it is .675!

Paul Lamar
 
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