Rusty,
Are you sure you’re allowing
yourself enough margin on the top end by using .55 bsfc. This chart (snitched
from the other list) indicates that .55 is about right up to around 7500, but at
8000 rpm bsfc will be up around .60. What does that do to your hp
numbers?
Mark S.
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Russell Duffy
Sent: Tuesday, March 22, 2005 2:25
PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: fuel
injector size, and redrive losses
RC Engineering's calcs show that you are good to 302 HP at 43 psi fuel
pressure, .50 BSFC, and 100% duty cycle. Of course you can't run the
injectors at 100% (except maybe briefly like a drag race, not applicable to
aircraft). So at 80% duty cycle the 38 lb injectors should be good for
242 HP. Enjoy your idle!!! Your injectors are big enough unless you
P-Port and turn at least 8000 RPM.
RC Engineering's calc shows the same as the
fuel calculator that I posted the other day. Four 38 lb/hr
injectors, at 80% duty cycle, .55 BSFC, should be good for about 220 HP at
the flywheel. I imagine that will be enough for the current engine,
but not by a wide margin. I plan to run this engine as high as
8000 if I can, though I'll be amazed if I can get beyond 7500. Don't need
no stinkin' P-Port for these rpms :-)
On the fuel spreadsheet that I posted
(stolen) the other day, it gives a HP figure for the flywheel, and rear
wheels. The estimate for the power loss due to a manual
trans and diff is 15% on this spreadsheet. Anyone know what
this amounts to for our redrive, and prop?
Rusty (hoping Ed out types me)