On the dyno, I had measured BSFC of 0.49 for lean cruise settings to 0.54
 for WOT 5000 rpm, lambda of about 0.93 (max power mixture).

 So when I'm cruising at 7500' at 170 KTAS I see 9.3 gph.  Assuming a BSFC of
 about .5 means a power of about 115 hp (mogas weighs 6.18 #/gal).  That's a
 believable number. That's 21 mpg (statute).  At 183 KTAS (210 mpg) the fuel
 burn was 11.2 gph, about 19 mpg.  Not bad.

 When I'm taking off at WOT and about 5400 rpm I see about 19 gph.  My dyno
 hp curve shows about 230 sea level, standard day hp for that rpm.  Adjust
 that for 1500' elevation and using a BSFC of .54 says I should burn 18.7
 gph.  That's very consistent.

 My dyno curve also says 270 hp @ 6200 rpm. Adjust that to 7500' (about 80%)
 and varying the speed as the cube root of hp says if I get 170 KTAS at 115
 hp, I should get 210 KTAS at WOT and 6200 rpm.  Guess what - actual speed
 for those conditions was 208 KTAS readout on my GRT EFIS.

 It all hangs together. (Don't forget that SAE rated hp is normalized to sea
 level, 60F day.)

 These BSFC numbers should be fairly consistent with what a Lycoming could
 get.  The fact that I get better fuel economy than the Lyc powered Velocitys
 suggests that I have a bit lower drag.

 This also suggests that the 20B on my Velocity doesn't ever have to really
 work very hard.

 Al

 http://www.velocityaircraft.com/newsV5/al.html
 http://members.cox.net/alg3/airplane.htm
 http://www.rotaryeng.net/Velocity_Vignette.wmv

Sweet!!

:)


Matt-


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