Message-ID: <3C5F504A.954F864B@earthlink.net>
Date: Mon, 04 Feb 2002 22:23:54 -0500
From: Marcelo Pacheco <macpacheco@earthlink.net>
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To: lancair.list@olsusa.com
Subject: Re: Engine dynamics
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The leaky exhaust valve issue isn't caused by proper LOP operation.

It's caused by running the engine very close to peak temps.

Typically, single engine EGT gauges are installed on the cylinder known to be
the leanest. So on such system, when you think you're running all cyls at 50
degrees LOP, you're probably running some cyls rich of peak, some very close to
peak, and hopefully at least one lean of peak. The ones at or just rich of peak
are the troublesome ones.

If you have proper (even) fuel and air distribution to all cylinders, then there
should be no problems from running the engine 50 or more degrees lean of peak.
The only way you can be sure this is happening is if you have an all cylinders
engine monitoring package, and depending on the engine, you'll need GAMIjectors
to achieve that good fuel distribution. For example, IO-320 or 360 are known not
to have good fuel distribution with stock injectors.

By the way, I'm just someone who pretends to understand this stuff. The people
that really understand are the engine professionals. I'm just a computer geek
with some aviation experience that likes to read about engines and have physics
knowledge you get out of a computer engineering degree. I read all John Deakin
articles from beginning to end and I think I understood them completely (you
never do, but I still think).

Now, if you're running a non-turbo charged engine at a high enough altitude
where your power output will be about or lower than 65%, then running the engine
just lean of peak is a better idea, as available power goes down from there. For
example, above 10k, I would run any non-turbo charged engine at max MP, 24-2500
rpm and just lean of peak mixture to get maximum power. I would climb full rich
until less than 25" MP is available, where I would start a little leaning to get
some more power. Below 10K, I would run them at full throttle, 2400-2500rpm,
leaning to obtain a fixed fuel flow which gives me the power output I want,
let's say 70% power. If the MP is higher than the MP setting where that fuel
flow results in peak temps, then you'll be lean of peak by definition.

My personal theory about why some engine manufacturers say their engines aren't
to be run LOP is they want to assume all their customers are dumb and can't lean
properly, while also being incapable or don't think there's financial return in
competing with GAMI. But that's just one of my many conspiracy theories.

No, I'm not financially associated with any airplane/engine/accessory company.

Marcelo Pacheco
PP-ASEL IFR 220 hrs
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