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From: "Tracy crook" <lors01@msn.com>
To: flyrotary@lancaironline.net
Bcc: 
Subject: RE: [FlyRotary] Re: Fw: Different Rotary Port configurations
Date: Tue, 19 Jun 2007 11:13:23 -0400
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The very best (economy wise)  piston engine designs today use variable 
overlap. The Prius engine may not have this feature because I think it 
operates at a very narrow rpm range so it is a different case.  The BMW 
(straight 6s) vary both intake & exhause timing to make good power and 
economy(for a performance car)  across the rpm range.  Laura's 330i gets 32+ 
mpg at 65 -70 mph.

>"getting the engine to pump the most air at a given RPM is "THE WAY."

There is absolutely no arguing this (correct) point but it only applys at 
WOT (where the 26B and most all race engines) operated.   This is where the 
best SFC happens due to minimum pumping losses.   But I think the pumping 
losses argument goes out the window as soon as you back off the throttle and 
manifold pressure goes down.   Sucking air past that damn butterfly takes 
energy.  You can operate at WOT and get good SFC but this ignores the real 
world factor that the aerodynamic losses on the airframe go way up at the 
higher airspeed.  This is the dominant factor so in reality, all these BSFC 
arguments are sort of moot unless you are racing.  But fun to discuss none 
the less.

Tracy


>
>
>Bob,
>  The engine in a Toyota Prius has overlap. My point is that it is NOT the 
>sole determination of economy. This isn't the biggest factor for 
>efficiency. I believe managing charge contamination is important, sure but 
>not the only factor. I think the new direct injection systems will work 
>very well with the rotary. The point is that getting the engine to pump the 
>most air at a given RPM is "THE WAY."
>Bill Jepson
>
>-----Original Message-----
>From: bmears9413@aol.com
>To: Rotary motors in aircraft <flyrotary@lancaironline.net>
>Sent: Tue, 19 Jun 2007 5:54 am
>Subject: [FlyRotary] Re: Fw: Different Rotary Port configurations
>
>
>
>And let me assure you, a P port will NOT get the same GPH. Theres a lot of 
>fuel wasted with the P Port due to the overlap in timing.
>
> 
>
>Bob Mears
>
>Supermarine Spitfire
>
>
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