Lean burn engines

[Bruce]

60-80% of the heat absorbed into the engine from the reaction is thru the
exhaust valve, and it's guide.   Depending on the amount of heat generated
you can exceed the thermal limits of the metal, and then it just blows off,
similiar to the dome of a piston when detonation is present.   Also, when
running that lean you might be in trace detonation, and localized heating of
some components is even worse.

Thermal barrier coatings will help, some.

The engine mixture is actually a small consideration.  It's going to take x
amount of energy to move a vehicle a certain distance.   Just actually
getting the tune right will get you close, all the exotic stuff is just for
small gains.

Using something more accurate then a ProJection would be my first
suggestion.  If you're going to run other then 14.7:1 (closed loop) then
you'll need to get 1/2 serious with the engine management.
Bruce


----- Original Message -----
From: "Ray Drouillard" <RayLists at quixnet.net>
To: <diy_efi at diy-efi.org>
Sent: Wednesday, October 17, 2001 6:47 PM
Subject: Lean burn engines


> I have heard that running an engine too lean will cause it to run hot, and
> will burn out the valves.  I have never seen an explanation of this.  Why
> does it happen.
>
> Generally speaking, how lean can I run a standard (normally aspirated)
> engine.  Specifically, (if it makes a difference), I want to improve the
> mileage of my Jeep Wagoneer, which has an AMC 360 V-8.  It is fed with
> Holley Pro-Jection, and is fired with a Jacobs Omni-Magnum ignition box.
>
> What can be done to an engine to allow it to run leaner.  The engine is
> currently at the rebuilder (though he hasn't started yet), so I might be
> able to get stellite valves or something like that.
>
>
> Ray Drouillard
>
>
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