Engine mixture guidelines

Jose wrote:



Google "lean of peak". There is a company out there (whose name escapes
me right now) that makes engine gauges that are supposed to be so good
you can run LOP safely.


It's not the gauges, it's the fuel distribution. In order to run LOP
effectively each cylinder must peak at the same, or damned close, fuel
flow and therefore at the same time.

It's not the gauges, it's the fuel distribution. In order to run LOP effectively each cylinder must peak at the same, or damned close, fuel flow and therefore at the same time.

Yep, you're right. And this usually requires an engine mod, since stock
airplane engines are not very uniform. In any case, don't these mods
also come with a gauge for each cylender?

Jose
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Newps writes:

The initial lean should be very quick. It's called the "Big Pull."
Fine tune as slow as you need to. You need to avoid the red box, that's
why you lean quickly.

The red box?

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Tony writes:

For that matter, if you do get peak power at max EGT, why run on the
rich side? Wouldn't it make sense in terms of fuel economy to run on
the lean side a bit?

Aside from the most fuel-efficient mixture settings, which settings
are the _safest_? Which settings put the least wear and tear on the
engine?

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J. Severyn writes:

It is called the "red fin" in this write-up by Cirrus....same thing.
http://www.cirrus147.com/training/LOPops-3-195278.pdf

OK, I think I've got it. The red box is the area where you heat up
the engine enough to reduce engine life over the long term, without
any clear advantage for fuel consumption or power. If you are leaner
or richer than the box, you get longer life and a better power/fuel
trade-off.

Mxs, maybe we can get you to fly a real aircraft if we keep this up.

That would require lots of time, lots of money, and some other things.

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Here's a useful URL.

http://www.atlasaviation.com/externa...enginest%2Ehtm

On Dec 31, 1:05 am, Newps wrote:
Jose wrote:
The initial lean should be very quick. It's called the "Big Pull."
Fine tune as slow as you need to. You need to avoid the red box,
that's why you lean quickly.

I've only heard of a red fox, not a red box. What is that?At and below 60% there is no red box, put the mixture anywhere you want.

At 65% power use richer than 100 ROP or leaner than peak.

At 70% power use richer than 125 ROP or leaner than 25 LOP.

At 75% power use richer than 180 ROP or leaner than 40 LOP.

At 80% power use richer than 200 ROP or leaner than 60 LOP.

As you transition from takeoff power to cruise power if you are going to
be LOP make sure you lean rapidly to the values listed for LOP ops.
Fine tune as necessary.

"Mxsmanic" wrote in message
...
J. Severyn writes:

It is called the "red fin" in this write-up by Cirrus....same thing.
http://www.cirrus147.com/training/LOPops-3-195278.pdf

OK, I think I've got it. The red box is the area where you heat up
the engine enough to reduce engine life over the long term, without
any clear advantage for fuel consumption or power. If you are leaner
or richer than the box, you get longer life and a better power/fuel
trade-off.

Mxs, maybe we can get you to fly a real aircraft if we keep this up.

That would require lots of time, lots of money, and some other things.

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Bingo! You've got it.

The red box is also where high peak internal cylinder pressures are
encountered. The combination of the high temps and high internal pressures
are detrimental to the life of the engine, and tend to thin out the owner's
wallet very quickly. (or worse)

The same power output (but less than max power) can be attained ROP and LOP,
but the engine runs cooler and more efficiently LOP. But the pilot must
ensure he/she is LEAN enough to stay out of the red box.

If the pilot needs maximum power (say during max. gross weight takeoff),
then ROP operation is normal. But again, the pilot must ensure he/she is
RICH enough to stay out of the red box. Fuel economy is not an issue during
the takeoff......just max power to clear obstacles and safely climb to a
cruise altitude.

Mxs, if you ever make it to the San Francisco Bay area, look me up. I'll
get you a few hours in the air where you can try it out yourself.

John Severyn

J. Severyn writes:

The red box is also where high peak internal cylinder pressures are
encountered. The combination of the high temps and high internal pressures
are detrimental to the life of the engine, and tend to thin out the owner's
wallet very quickly. (or worse)

The same power output (but less than max power) can be attained ROP and LOP,
but the engine runs cooler and more efficiently LOP. But the pilot must
ensure he/she is LEAN enough to stay out of the red box.

If the pilot needs maximum power (say during max. gross weight takeoff),
then ROP operation is normal. But again, the pilot must ensure he/she is
RICH enough to stay out of the red box. Fuel economy is not an issue during
the takeoff......just max power to clear obstacles and safely climb to a
cruise altitude.

It seems, then, that the only reason to cross through the red box is
to improve fuel economy (?).

Overall, based on some conflicting stuff I've read in various places,
I've managed to distill a handful of fairly common recommendations:

- Use full rich on take-off and landing, unless you're at a really
high altitude

- At other times mixture isn't critical, but leaning slightly with
altitude saves fuel and provides more power.

It sounds like you can fly around with full rich all the time if you
want, except that you'll waste fuel and potentially dirty the engine
in time. More reasonably, you can lean a bit as you get higher in the
air, reducing fuel consumption and possible dirtying of the engine.
Tweaking the mixture beyond that can save more fuel and (perhaps)
somewhat reduce engine wear, but it requires a lot more attention.

Does this more or less look correct?

Mxs, if you ever make it to the San Francisco Bay area, look me up. I'll
get you a few hours in the air where you can try it out yourself.

It's unlikely I'll be anywhere near KSFO in the foreseeable future,
except in simulation. If you're on VATSIM and you spot a Baron with
tail number N9119E or a Boeing Business Jet 2 with tail number N9119F,
that's probably me. At this particular instant I'm parked at Gate 10
at KSAN, but not for long, as I'll be returning to KPHX shortly.

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Mxsmanic wrote:
Up to now when flying in simulation, I've had the simulator take care
of engine mixture adjustments. However, since I'd have to do this
myself in real life, I've decided to make some modest attempts at
managing mixture myself.

Making whole-hearted attempts may prove most effective.
-----

- gpsman

Jose wrote:
It's not the gauges, it's the fuel distribution. In order to run LOP
effectively each cylinder must peak at the same, or damned close, fuel
flow and therefore at the same time.


Yep, you're right. And this usually requires an engine mod, since stock
airplane engines are not very uniform. In any case, don't these mods
also come with a gauge for each cylender?


No, the GAMI's are six injectors that replace the standard six. They
reccomend an engine monitor but it's not necessary. As it happens I can
run real nice LOP without having to buy the GAMI's.