Leaning out the mixture on the ground Op's

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gege21
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Re: Leaning out the mixture on the ground Op's

Post by gege21 »

Piper_EEWL wrote:Yes those A2A planes bring so many hours of enjoyment!

Happy flying
I just bought the C182T yesterday and haven't yet fly with it to day... I only read all the manual from the beginning to the end...Took some time ;) but the history is very interesting plus the how to manage to run this bird correctly is truely attractive.

I will go to discover this superbe airplane...
Thanks

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Gerard
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t.manua
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Re: Leaning out the mixture on the ground Op's

Post by t.manua »

That's a very interesting discussion. I'm having issues leaning the engine on the ground though. The problem that I have is, when I get the RPM to 1200 and start leaning, very slowly and gently, the RPM starts dropping instantly, I don't record a slight rise in RPM, not the slightest. The AGL is about 150ft. OAT is -1.

The other issue is when I'm leaning for cruise. I've read that's its recommended to lean 100F rich of peak. I'm in the air right now at 6000ft, I lean the engine to peak EGT and the increase the mixture until I'm at 100F rich of peak, what happens is that I'm ending up with a full rich mixture, almost. But to my knowledge it's not advisable to run the engine at peak EGT. So I'm leaning for 50F rich of peak.

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Oracle427
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Re: Leaning out the mixture on the ground Op's

Post by Oracle427 »

Proper leaning for cruise is between max EGT and 50 degrees ROP. Max EGT will provide max duration and 50 ROP will provide an optimal cruise balancing duration and speed.

100 ROP is just shy of a full power mixture of around 125 ROP. Lots of fuel being wasted there for no gain.
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t.manua
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Re: Leaning out the mixture on the ground Op's

Post by t.manua »

OK, thanks Oracle. Yeah, 100F ROP just sounded too much.

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Piper_EEWL
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Re: Leaning out the mixture on the ground Op's

Post by Piper_EEWL »

t.manua wrote:OK, thanks Oracle. Yeah, 100F ROP just sounded too much.
Yes but 100F ROP at 6000rpm shouldn't result in a full rich mixture I think!? I can't check right know but it sounds wrong. How do you lean for peak EGT? Are you allowing enough time for the EGT to stabilize?
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Oracle427
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Re: Leaning out the mixture on the ground Op's

Post by Oracle427 »

Correct that 100ROP at 6000 feet would not be the same as if at sea level for a given RPM.

100 ROP whether at sea level or at 6000 feet should yield more or less the same fuel flow for a given RPM, and it will be wasting fuel during cruise. It is very close to "full rich" at sea level.

If you move the mixture to the physical full rich position, it will be dumping copious amounts of unburned fuel out of the exhaust and power will be greatly reduced. There is a graph from Lycoming that Akar published here some time back. IIRC, it shows the relationship between EGT, Power and CHT.
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AKar
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Re: Leaning out the mixture on the ground Op's

Post by AKar »

IMO, the current A2A engine simulation behaves a bit weirdly at rich, as if not really running rich enough, but I've never plotted the response or anything. Might as well play with it some one day to be more specific.

For ground leaning, I'd just pull the mixture until the engine starts to run bad or power loss occurs, and then increase just enough for smooth running. This also works for cruise leaning, if you don't want to concentrate on the EGT gauge: lean until roughness / power loss, and enrich just a bit to restore. It gives you about the best economy mixture as a result.
t.manua wrote:But to my knowledge it's not advisable to run the engine at peak EGT. So I'm leaning for 50F rich of peak.
That shouldn't be a problem at all when done sensibly, actually all else equal, the 50 °F would be more "stressing" to the engine.
Oracle427 wrote:There is a graph from Lycoming that Akar published here some time back. IIRC, it shows the relationship between EGT, Power and CHT.
Like so. :)

Image

-Esa

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Re: Leaning out the mixture on the ground Op's

Post by t.manua »

Piper_EEWL wrote:
Yes but 100F ROP at 6000rpm shouldn't result in a full rich mixture I think!? I can't check right know but it sounds wrong. How do you lean for peak EGT? Are you allowing enough time for the EGT to stabilize?
I set an RPM, 2200 for example, then I start gently reducing the mixture. At a certain point the RPM starts to increase, by maybe 25 to 50 RPM. I continue to reduce the mixture until I notice an RPM drop, I increase the mixture just enough to increase the RPM to the point before it started to drop. I wait for the EGT needle to stabilise and note the value, then I continue to push in (increase) the mixture until I'm 50F ROP. If I would increase the mixture to 100F ROP, I'll end up pretty much at a full rich mixture.

I've read that running the engine at peak EGT is not advisable, over a long term, since the cylinder head temperature is fairly high and can decrease the life expectancy of the engine. Is this part even simulated in the A2A 172?

Thanks for the graph AKar, very interesting.

-Tom

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Oliver Branaschky
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Re: Leaning out the mixture on the ground Op's

Post by Oliver Branaschky »

I've read that running the engine at peak EGT is not advisable, over a long term, since the cylinder head temperature is fairly high and can decrease the life expectancy of the engine. Is this part even simulated in the A2A 172?
Hi Tom,

See Esa's graph: At peak EGT you're actually on the cold side of peak CHT, whereas at 50°F ROP you're pretty much spot on at peak CHT. So running your engine at 50°F ROP is actually the worst you can do in regards of CHT.


Viele Grüße | Best regards,
Oliver

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AKar
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Re: Leaning out the mixture on the ground Op's

Post by AKar »

t.manua wrote:I've read that running the engine at peak EGT is not advisable, over a long term, since the cylinder head temperature is fairly high and can decrease the life expectancy of the engine. Is this part even simulated in the A2A 172?
Well, to this problem running the engine at 50 °F rich of peak would not be a solution: if anything, the cylinder head temperature is even higher, everything else being equal. Still, this doesn't mean that even if you ran the engine at 50 °F rich of peak, or at peak or wherever, the cylinder head temperatures are necessarily excessively high in absolute terms. At reduced power levels (limited either by the throttle reduction or by altitude), and with sufficient cooling airflow, the CHTs can remain reasonably low at these mixture settings too.
Piper_EEWL wrote:Yes but 100F ROP at 6000rpm shouldn't result in a full rich mixture I think!? I can't check right know but it sounds wrong. How do you lean for peak EGT? Are you allowing enough time for the EGT to stabilize?
I recall I've had difficulties to see much more than that of a drop in EGT by going full rich at low altitudes in A2A Comanche at least, running at high power levels. As if the full-rich wasn't that rich it ought to be. Anyways, this is actually something I might specifically test for once, to see if it is really so.

-Esa

t.manua
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Re: Leaning out the mixture on the ground Op's

Post by t.manua »

Hey Oliver and Esa,

upon taking a closer look at the graph I'm really surprised to see that. You're absolutely right, the CHT is actually lower at peak EGT than at 50F ROP. That's very interesting and I just learned something new.

Thanks for that!

- Tom

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