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Date: Mon, 11 Feb 2008 09:08:32 -0500
From: Ernest Christley <echristley@nc.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Fuel burn
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Greg Ward wrote:
>
>   O.K., time to throw a little F matter into the fan.  I am sitting in =
my new shop, with a Lancair Legacy RG, and a relatively new 20B "D" serie=
s on a palette.  I got the engine complete with everything it had in the =
Cosmo that it came out of.  There isn't even a coat of grease on this thi=
ng.  Radiator, oil cooler, air conditioner, condenser, ECU, injectors, co=
ils, motor mounts, and about 100 pounds of extra stuff came with it.  My =
buddy (he has been selling engines for 15 years) in LA that sold me this =
engine ($4500.00) is in constant contact with people who race this motor,=
 and I am getting a lot of input on how to set this thing up.  I have ord=
ered Tracy's gear drive, and plan on generating 400 HP on take -off, and =
about 75-80% at cruise.  My max rpm will be 8000.  You have no idea how m=
uch input I am getting from the racing set.  They are saying that with a =
variable boost (electronic) controller, I can vary the boost at any given=
 altitude, as much or as little as I want, and tweak this thing for max p=
erformance.  They can't believe that I am asking so little from this engi=
ne.
>
>   This will get us started;
>   Greg
>  =20
Greg, I don't want to rain on your parade, but there are three questions =

you have to ask yourself:

- Can I reliably pull that many horses out of the motor for hours on end?=

- Can I carry enough fuel to support pulling that many horses for hours=20
on end?
- Can I keep the engine from melting while pull that many horses out of i=
t?

It's been demonstrated on this list several times that not everything=20
from racing translates directly to airplanes.  For instance, 400Hp will=20
require twice the radiator volume that most of us are using, along with=20
the larger associated ducting and cooling drag.  Will the reduction in=20
reliability and increased fuel burn be paid for by the extra speed once=20
the effects of the extra weight and cooling drag are factored in?  ie,=20
you will go faster, just not as much as "double the Hp" would imply,=20
because of the cooling drag.  I don't think most racers have to worry=20
about that to much, but you could wind-up with a system that just cost=20
you more to go to only relatively close places faster.