From: Epijk@aol.com
Message-ID: <ea.2087d44e.2967b579@aol.com>
Date: Fri, 4 Jan 2002 20:48:41 EST
Subject: Re: BMEP (again!)
To: lancair.list@olsusa.com
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Reply-To: lancair.list@olsusa.com

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In a message dated 1/2/2002 6:40:26 AM Pacific Standard Time, glcasey@gte.net 
writes:

<<<...FMEP reduction, while desirable, is difficult to accomplish and has 
only a small
effect...>>>

Gary:
Beg to differ. Agreed, it is (a) desirable; (b) often not so difficult, but 
(c) CERTAINLY NOT insignificant. Example: by redesigning the oiling system on 
our development engine, we were able to gain about 15 HP (cruise) and 17.5 HP 
(takeoff). In another development, a redesigned coolant pump provided an 
increase of about 4 HP (cruise) with the same (high) coolant flow rate as 
before. There are more examples. I don't really think those kind of increases 
are insignificant. 19 HP without any increase in fuel consumption or heat 
rejection? I'll take that anytime. (And I know certain Winston Cup engine 
guys who would sell their sainted mothers into slavery for a definitive 4 HP 
increase.)

That being said, the point of my statement about FMEP was not to present it 
as an preferable alternative to raising combustion yield. THE POINT was, as 
stated, to demonstrate that BMEP is not directly related to the combustion 
process. (George was trying to make a similar point in a different way.)

<<<..the theoretical thermal efficiency of the Otto cycle is inherently 
linked to the peak pressure since it assume constant-volume combustion...>>>

Actually, the efficiency of a cycle with combustion at constant volume is a 
function of the ratio V1/V2, the calculated compression ratio (C.F.TAYLOR,  
IC Engine...., Thermodynamics, Volume 1, Chapter 2). And remember that these 
discussions relate to an isentropic process with reversible, adiabatic 
compression and expansion events. Look at the expressions which define the 
theoretical operation of the combustion-at-constant-volume cycle, and the 
proposed improvements become more clear.

THanks for your interest.
Jack Kane
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