Message-ID: <39E2A719.FDB86212@progress.com>
Date: Tue, 10 Oct 2000 01:20:25 -0400
From: Marcelo Pacheco <pacheco@progress.com>
Organization: PROGRESS Software Professional Services
To: lancair.list@olsusa.com
Subject: Re: TSIO 550 -E Lean of Peak or rich of peak
Reply-To: lancair.list@olsusa.com
Mime-Version: 1.0

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Jeff,

Disclaimer: I don't own a IV, I'm building my 360, and hope not to have
those issues by running a Diesel/Jet Fuel engine.

I have to admit that I've been converted by John Deakin (www.avweb.com),
as far my cessna flying is concerned. His argument is so thorough
technically, that it leaves little doubt:

"The only type of engine that shouldn't be run lean of peak is when fuel
distribution across cylinders is not even enough." - That's my bottom
line interpretation of his articles.

Running your engine lean of peak results in a cleaner exaust, because
you're using excess air, not excess fuel to limit combustion temps. This
means that all the fuel is getting burned unlike what happens when you
run rich of peak.

The issue is when you don't have good fuel distribution you get one of
two conditions:

1 - Some cylinders are lean of peak, some cylinders are rich of peak -
Not good
2 - Some cylinders are nicely lean of peak, some cylinders are so lean
there's no combustion - Even worse - That's what the roughness is all
about

But with the GAMIjectors, you should get such an even fuel distribution
you can lean your engine right down to the point you don't get any
combustion at all. No roughness because all cylinders quite burning at
the same time. Well that's the sole technical reason they're suposed to
be so great.

If you have individual cylinder engine monitoring package, you can
confirm that by watching how even your EGT's and CHT's will be as you
lean.

If you don't have such engine monitoring package, use a power setting
lower than 65% and see how far can you lean. If you can get 100 degrees
lean of peak, smoothly add power until you get the indicated airspeed
you'd get at 75% power settings. Remember that when using power settings
under 65%, any mixture won't hurt the engine by definition.

The bottom line is if you can get the power up while keeping the mixture
that low, you ARE alright. It's great for the engine to run drastically
lean of peak. It's not that great to run it just a little lean of peak.

Once you can get a 75% LOP setting, add MP while reducing mixture as
much as possible. The farther you can get the better for the engine.

The only potential negative factor is the turbos will be working harder,
which long term reduces their useful life. But it looks like you're
saving a lot more on fuel that on a shorter turbo life.

John Deakin's articles (http://www.avweb.com/toc/columns.html). All
that's said here is just interpretation of what he said.

Marcelo Pacheco
PP-ASEL IFR
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