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From: "Rumburg, William" <william.rumburg@cdicorp.com>
To: "'lancair.list@olsusa.com'" <lancair.list@olsusa.com>
Subject: RE: GAMIs for 4 cylinders
Date: Thu, 10 Jan 2002 18:53:32 -0500
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Reply-To: lancair.list@olsusa.com

          <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>>
          <<  Lancair Builders' Mail List  >>
          <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> 
>>
	Could you describe a bit why you decided to go with GAMIs and what
results you
	found with your engine pre and post.  Also, what instrumentation do
you have
	for temps?
	Much interested,
	Ed de Chazal
Ed-
Please pardon my taking awhile to respond. I've been working "offsite" and
away from my computer (and email)...
The effects of mixture variation on engine combustion dynamics are explained
by John Deakin on his AvWeb site
http://www.avweb.com/articles/pelperch/pelp0018.html 
LOP operation is a much kinder mode of operation for your engine than ROP.
It results in less engine stress and cooler CHTs; however, it can cause
objectionable roughness if cylinder power (fuel) flow isn't well balanced.
Very few engines have naturally well balanced fuel flow and those that do
have it by chance. I believe operation at 50 to 80 LOP to be optimum for
most engines.
Like you, I also have the VM1000 engine/fuel monitor. My CHTs have always
been 360-380 in the Summer and 300-340 in the Winter and well balanced,
usually no more than a 10 degree spread; however, my EGT spread was 80-100
with the Lycoming injectors and my engine wouldn't operate 30 LOP without
experiencing roughness. 
I bought the "stock" set of GAMI jectors for my engine model, in lieu of
submitting EGT/fuel flow data. The before and after results were impressive.
I taxi at 900 RPM and noticed right away that with GAMI jectors, I could
pull the mixture considerably further out (leaner) before roughness occured
and idle was smooth all the way down to 700 RPM! Furthermore, I could
operate 100 LOP before I felt the slightest roughness! My fuel flow went
from 7.4 GPH to 6.4 GPH at 180K IAS, 8K ft. and the extended range is
noticable on longer flights.
Bill Rumburg
N403WR  Sonic bOOm
 


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