Message-Id: <5.0.2.1.2.20010428081904.00a78090@olsusa.com>
Date: Sat, 28 Apr 2001 08:20:54 -0400
To: lancair.list@olsusa.com
From: Marvin Kaye <marvkaye@olsusa.com>
Subject: lean of peak
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Reply-To: lancair.list@olsusa.com

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POsted for "Brian Barbata" <barbatab001@hawaii.rr.com>:

I was right in there with those defending LOP operation, until I consulted 
with some of the best rebuilders around last year. I had been running my 
Bonanza 40 to 80 LOP (GAMIjectors/engine monitor) and recording the numbers 
for well over a year. I thought I could defend the reasoning and the 
results to anybody. I had read all the articles. I had talked to GAMI. In 5 
minutes with an unbiased, experienced authority on the subject, I was 
convinced that the risks of an inadvertent detonation far outweigh any 
possible benefits of LOP. Rebuilders will tell you they can almost always 
spot an engine that has been run LOP for a significant time. Saving fuel 
does not justify LOP (maybe you are in the wrong hobby!). Thinking you're 
saving the engine does not either. You will burn a couple of more gph by 
running ROP. There is no basis for believing LOP prolongs engine life or 
avoids catastrophic failures. So, for 5 bucks an hour, you are willing to 
risk detonation? For a more convincing discussion of this, call John Pava 
at Victor Aviation ("Black" engines) in Palo Alto at (800) 207-0061. Hard 
to argue with experience. I'm much more comfortable flying over the ocean 
100+ ROP (best power = best speed).

BTW, if lower pressures were instrumental in preserving engines, we would 
all have engines with design cylinder pressures below 40 psi! Someone did a 
test to determine if pilots were prematurely getting overhauls "to regain 
power" because of cylinder pressures below 60 (seems to be a magic number). 
They began filing down the compression rings on a TCM on a dyno, and 
recording the power output and the pressures under lab conditions. Guess 
what! There was almost no reduction in power until they got below 40, and 
even then, it was minimal. They stopped the test because they feared 
blowing out the sump with the blow-by! Not that we shouldn't pay attention 
to these numbers, but sometimes they don't produce the effect we logically 
assume.

Brian Barbata

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