Leaning using EGT - Lycoming O-540 (Aztec)

[Dean]

On my first flight in the Aztec with a fellow pilot who was doing the
flying, he stated to lean using the EGT (a recently installed
Electronics International digital single probe device)to circa 1300 and
no higher than 1350.

The aircraft does not have a CHT.

I am totally new to operating larger engines like the O-540 (no fuel
injection here) and want to ensure I dont damage anything. I hear a lot
of talk and hearsay about LOP/ROP leaning procedures.

Like most owners, I want to operate my aircraft efficiently, but not to
the detriment of engine reliability.

Any advice is welcome.

Regards,

Dean

[Doug]

Take it up to 10,000'. Push the throttle and prop full forward. Lean to
maximum rpm. Note your EGT. Now, for ALL operations, lean to that EGT
(or as high an EGT as you can get). You will be running rich of peak.
Quite a bit rich at high power settings, to running at peak at the
power setting at 10,000'. This is usually about 1350 F on the EGT.

[Jim Burns]

Dean, check out this pps. And as others have said in other "leaning"
threads, check out John Deakin's articles on avweb.

http://www.avweb.com/other/Leaning.pps

Without an electronic engine monitor in our Aztec, I usually lean to 75-100
ROP using the EGT and sacrifice some fuel. My primary goal is to keep our
CHT below 400 and the oil temp below 200, using cowl flaps as necessary

Jim
..

[Thomas Borchert]

Dean,

absolute values of EGT are irrelevant with respect to leaning.
Completely and totally so. What is relevant is the relation to peak EGT
you are at, regardless of what the absolute value for peak is.

Thus, when you have set cruise power, you lean until the EGT indication
peaks and then falls again. That is your peak setting. Then, under
consideration of what the POH says and what people like John Deakin
say, either continue operating at peak (or lean of it, if your engine
will do that) or enrichen to 100 to 150 rich of peak, that is, until
the EGT falls from peak by that amount of degrees. Again, absolute
value is irrelevant.

Your engine is carburetted, so it will probably not run lean-of-peak
without considerable roughness.

Also, you should aggressively lean during taxi on the ground. You
cannot harm the engine at all by leaning at taxi power settings. Lean
at taxi power until the RPM just rises a little bit. If you lean
further, the engine will stumble or quit. That's where you want to be.
Now, should you forget to enrichen again for take-off (or even the mag
check), the engine will stumble or quit since you have leaned it so
aggressively. This prevents you from taking off leaned accidentally.

--
Thomas Borchert (EDDH)

[Thomas Borchert]

Doug,

> Now, for ALL operations, lean to that EGT

Why?

> This is usually about 1350 F on the EGT.

Why is that number relevant?

--
Thomas Borchert (EDDH)

[Dean]

Thanks for the information. I'm already leaning on the ground quite
aggesively as i've been told the O-540 plugs foul really easily with
the very rich mixture the Aztec is set-up for full rich.

One last question (sorry for the ignorance) but how do I know that that
particular EGT is the highest reading. i.e. is it taken off an
individual exhaust outlet or further down the exhaust (i.e.
common/averaged reading). Just wondering what the case is if the EGT is
out, and you lean to an incorrect EGT figure?

Dean

[Newps]

Doug wrote:
> Take it up to 10,000'. Push the throttle and prop full forward. Lean to
> maximum rpm.

No good. He has constant speed props. The rpm won't change until he
pulls the mixture control all the way out.

[Jim Burns]

Just pull the side cowls and look to see where the probe is installed.
Jim

"Dean" > wrote in message
oups.com...
> Thanks for the information. I'm already leaning on the ground quite
> aggesively as i've been told the O-540 plugs foul really easily with
> the very rich mixture the Aztec is set-up for full rich.
>
> One last question (sorry for the ignorance) but how do I know that that
> particular EGT is the highest reading. i.e. is it taken off an
> individual exhaust outlet or further down the exhaust (i.e.
> common/averaged reading). Just wondering what the case is if the EGT is
> out, and you lean to an incorrect EGT figure?
>
> Dean
>

[Doug]

Works on my plane (a Husky with Constant Speed prop). The idea is that
at 10,000' you can lean all you want and it won't hurt anything, at
full power for that altitude. Now, you will be rich of peak, just a
little rich at 8000' full power, and so on down to Sealevel where you
will be 150 or so rich of peak. Works great. You are leaned enough to
be rich of peak and you don't even have to go to peak, at Sealevel
(which can cause detonation), to find out where peak is. You will be
leaned enough rich of peak to be safe, but not so rich as to waste fuel.

[[email protected]]

Unfortunately, for a carb'd O-540 like that, having an EGT gauge isn't too
terribly useful for leaning in cruise. It *is* useful for progressive leaning during
a long climb. That is, note the full-rich, sea-level, max-power takeoff EGT and lean
during the climb to hold that (e.g. 1300).

For cruise, however, you'd be better off ensuring running at 70% or less, and
leaning as much as possible, all the while ensuring that CHT never goes above 375.
If it does, enrichen so it doesn't. If over 75%, enrichen to that same "full-rich"
EGT (e.g. 1300). Likely the O-540 will run with a few cylinders lean of peak, a few
at peak, and a few richer than peak when leaned fully to roughness. That's as good as
you can do... just keep the power at 70% or lower.

<flame suit activated> :)
-Cory

Dean > wrote:
: On my first flight in the Aztec with a fellow pilot who was doing the
: flying, he stated to lean using the EGT (a recently installed
: Electronics International digital single probe device)to circa 1300 and
: no higher than 1350.

: The aircraft does not have a CHT.

: I am totally new to operating larger engines like the O-540 (no fuel
: injection here) and want to ensure I dont damage anything. I hear a lot
: of talk and hearsay about LOP/ROP leaning procedures.

: Like most owners, I want to operate my aircraft efficiently, but not to
: the detriment of engine reliability.

: Any advice is welcome.

: Regards,

: Dean


--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[Newps]

Doug wrote:
> Works on my plane (a Husky with Constant Speed prop).

If you can change your engine speed with the mixture then you have a
governor problem.

[Dean]

Cory,

This is what I was concerned about, letting the CHT go over 400 without
realising it, having no CHT installed. In cruise I am running less than
75% so this shouldn't be a problem. Instead of fitting an expensive
engine monitor I may just purchase a digital CHT so I can see what's
going on, however the panel space is pretty tight at present.

Dean

[Thomas Borchert]

Dean,

> Instead of fitting an expensive
> engine monitor
>

Expensive is relative here. The things are cheap compared to one (or,
in your case, two) engine overhauls.

--
Thomas Borchert (EDDH)

[Thomas Borchert]

Dean,

> but how do I know that that
> particular EGT is the highest reading. i.e. is it taken off an
> individual exhaust outlet or further down the exhaust (i.e.
> common/averaged reading).
>

You don't. But again: You are not looking for the highest value in EGT.
What you are looking for is the first cylinder to reach peak,
regardless of the value it is at. The Deakin columns make all this
clear (after a while...).
The only way to make sure is to install a multi-probe EGT instrument.
Actually, with your kind of engine, I would recommend having one.

But, as long as you don't have one, using the one probe you have will
put you in the ballpark.

--
Thomas Borchert (EDDH)

[[email protected]]

Dean > wrote:
: Cory,

: This is what I was concerned about, letting the CHT go over 400 without
: realising it, having no CHT installed. In cruise I am running less than
: 75% so this shouldn't be a problem. Instead of fitting an expensive
: engine monitor I may just purchase a digital CHT so I can see what's
: going on, however the panel space is pretty tight at present.

Like I was trying to say before, for simple, crude engines like the O-540,
having a whole bunch of readouts probably won't do a whole lot of good. They'll be
all over the map and not much you can do about it.

That said, the first thing I did on my O-360 was install a CHT and EGT probe
for each cylinder. I didn't buy an analyzer, just the Westach gauge and a switch. I
ended up buying the "STC'd" kit, but in reality it's the same thing as the non-kit.
In fact, the rotary switch they supply is pretty cheap and has already become a bit
oxidized internally after 3 years. After switching, you have to wiggle it a bit to
make sure you've got really good internal contact. I'd like to replace it with a
better switch with internal gold-plated contacts.

Depending on how cozy you are with your mechanic (and its corollary of how cozy he is
with your local FSDO), I'd suggest something like this:
http://www.westach.com/images/showcase/2A1P-CHT_Pointer.jpg
or maybe
http://www.westach.com/images/showcase/2DA8-Dual_CHT.jpg
or
http://www.westach.com/images/showcase/2DA1-Dual_EGT-CHT.jpg
to conserve panel space.

A rotary switch (all that the STC kit has, anyway) can be wired in to select
whichever jug you want to look at. That makes the primary cost simply that of the
probes. Like I said, I put multiprobes on mine, but in reality I rarely switch. I
found which one was hottest (right-rear, generally) and leave it on that.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************