Message-ID: <3AE9F8F9.60A4EAAA@progress.com>
Date: Fri, 27 Apr 2001 18:55:53 -0400
From: Marcelo Pacheco <pacheco@progress.com>
Organization: PROGRESS Software Professional Services
MIME-Version: 1.0
To: Lancair Mail List <lancair.list@olsusa.com>
Subject: Re: Running lean of peak
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Reply-To: lancair.list@olsusa.com

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> The word "new" is operative here.  How many of these engines are in the
> air, and how many total flying hours do they have?

Yes, but GAMI has some instrumentation on a test stand that is capable of
graphing a cylinder pressure through the combustion cycle with enough resolution
with amazing resolution. They show there how much better running lean of peak
is. It seems like you're so ingrained in the no LOP that you never even read
through the LOP articles on Avweb. Look at:

http://www.avweb.com/articles/pelperch/pelp0033.html

The information there is VERY HOT !!! Specially the chart (here's the link just
to the chart):

http://www.avweb.com/articles/pelperch/graphics/pp33_rich_to_lean_lg.jpg

This shows the pressure versus degrees before and after TDC (top dead center) of
an IO-470 in various power settings. It will show that running an engine
100 degrees LOP is much better than running an engine 100 degrees ROP, because
the
pressures inside of the combustion chambers are way lower and they build far
more slowly, reducing the amount of combustion energy hitting the pistons right
about when they're at TDC, where most of the energy operates trying to break the
crankshaft, break the pistons, instead of generating usefull crankshaft energy.
Well let me stop trying to write the article to you before I get too caried
away. This is due to the combustion happening in a slower, more controlled
fashion (the exact oposite of detonation)

> When they have half a hundred engines flying with a 1700 hours each without
> burned up cylinders,  we should give their technique serious 
> consideration.

If hard measurement data is not worth a damn to you, then that's your way to go.
Not mine. No offense intended please.

> If they cannot substantiate it because of lesser numbers, I would not want
> to be their test pilot contributing my dollars to prove their theory.

John Deakin shows that he was able to lean his Turbo Normallized IO-550 engine
all the way to 8GPH. If you want to have a hassle free engine management
technique, don't run rich of peak by the numbers, just go 150-200 degrees lean
of peak. If you descend without pulling on the power nor changing the mixture,
you'll end up with an overleaned engine that eventually will stop producing
power, it will not overheat, because as you descend you're leaning the engine
further.

All I'm trying to tell you is there's enough data out there to prove that this
isn't a theory, this is FACT. If you want to be conservative, just lean to
12-13GPH, where the temps will be so low that if you should be concerned about
anything, it will be that your engine is just running to cold instead of too
hot. I believe that if you run your engine as rich as recommended on climb, then
lean way agressively on cruise, you will get 50% more durability out of it, as
the pressures and temps will be so much gentler on the engine.

When you reply, please let me know if you have actually looked and understood at
least the chart or better the whole article. Again, you'll be glad you did.
Aproach this information with an open mind and you'll start wondering if those
folks with burned engines are really running their engines LOP or just around
peak.

A reply to Tony's e-mail follows. Look carefully at the numbers he's showing.

>My IV-P operates just fine LOP. Here are my cruise numbers, 500 hours on 
>TSIO-550
>
>@25,000'.........2400 RPM,    29"MAP,    15GPH,   277 KTS TAS,     5PSI cabin.
>EGT's 1550          CHT's 290          TIT's 1580       OIL TEMP 180
>
>I get 5 hours range (1325 NM) and still land with one hour fuel.
>Its a no-brainer.
>I do have winglets, and cooling louvers under the cowl
>Tony Durizzi

Have you tried increasing MAP while leaning to maintain 15GPH ? This should give
you lower yet temps. Maybe not quite full throttle but a good boost from 29-30"
sea level ambient pressure. You're running a quite conservative power setting,
about 58% power (15GPH * 13.7 ~ 205.5HP -> 58% power), at lop, you can find out
what power setting you're running at by multiplying the fuel flow by 13.7 for
8.5:1 compression ratio engines.

This is exactly my point: CHT: 290, that's very, very cold, how can this ever
damage this engine. Tony have you ever performed a engine borescope to help us
convince the folks which are incapable of believing in it ?

Isn't the TSIO-550 recommended to be run at a minimum of 2500rpm ?

Thanks for the info,

Marcelo Pacheco
PP-ASEL
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