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Date: Fri, 20 May 2005 12:16:29 -0400
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From: "Gary Casey" <glcasey@adelphia.net>
Subject: Re: ECI "Titan" Cylinders
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<<Yes, this is the change in air temp as it leaves the manifold and is
heated by the intake chamber as it is going into the cylinder. Kinda tough
to measure on the fly. I don't have an air temp gauge right next to the
intake valve.>>

I've found that a good rule of thumb is that a change in inlet air temp
(before it goes into the engine/manifold) is worth about half as much as the
actual change.  In other words a 50F change is only worth 3% or less, not
the 5+% theory would predict.  The reason is that the temperature that
counts is the charge temperature in the cylinder as the intake valve closes
and the air is heated by the engine parts as it goes in.  By the same token
a change in CHT will probably change the charge air temperature less than
half as much as the change in CHT.  Bottom line is I wouldn't recommend
struggling to reduce Chat's to the lowest possible just to get better
volumetric efficiency.  Although science and engineering rule, I'm sure it
has something to do with Murphy's law - any improvement you make is worth
half as much as you predict, but things gone wrong hurt twice as much as
they should.

Gary Casey