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From: Gary Casey <glcasey@adelphia.net>
Subject: Ignition timing

All this talk about the relative merits of EI and mags brings up a  
question that I can't seem to get answered - maybe someone out there  
knows:
Just to keep it simple, I'd like to know the BSFC of an engine (my  
engine would be even better) running at 20 inches and 2500 rpm, LOP,  
with the following configurations - dual mags, std timing; one mag  
std timing and one EI optimized timing; and finally two EI's with  
optimized timing.  To put icing on the cake it would be good to see a  
timing sweep for each of the cases.  And even better a map over more  
of the operating range, including full power. I've got a parallel- 
valve IO-540 with 10:1 compression, one LSE-III and my engine builder  
set the base timing at 25 degrees.  He says that he sets all parallel- 
valve Lycomings at 25, even up to 12:1 and all angle-valve engines at  
20 degrees.  I'm uncomfortable having the setting at 25, but I have  
no data to support it.

Gary Casey