C182 leaning and the EGT gauge

Bonchie

Bonchie

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Bonchie
I'm new to a 182P and the POH says what I was always taught. Lean til rough, rich til smooth. I think it says one turn back in is best economy, two is best performance.

When I do that though, the EGT reads really high (CHTs are still well in the green). We've only got the old single probe with the "25*" divisions. It's got that fancy warning star above "400*" mark but to stay below it, you have to go many turns back in over the point where it gets rough. That means I'm nowhere near best economy according to the POH. So is it dangerous to use the POH's leaning method or is it safe to run higher EGTs in cruise?

I've tried to google answers for my specific circumstance, but they all seem to involve LOP operations and fuel injected engines.
 
What is really high?
You can only over lean if you are above 65% power (some say 75%). Look in the POH to see where that is. If you arent there, you just lean to roughness and richen to smooth. Look at the exhaust pipe when you land. There should be no black soot, just gray. And the spark plugs should not be black etc.
 
Over the 400 degree mark on the gauge with the star above it. I realize that's not the actual EGT temperature but what's the significance?
 
Following, since I fly a 182P and am curious about the answers
 
If this "new to you" 182 is your own personal plane I'd highly suggest a good engine monitor as a top priority. I put a JPI 830 in my Saratoga. No more guessing. Wouldn't fly without it.
 
I fly a Piper with a Lycoming, so my comments are general in nature, not specific to your plane or engine, but may be of some value for reference.

In general, EGT is not something to get too worried about. EGTs can vary widely depending on the probe placement. However, peak EGT is a reference point for leaning. For my engine (Lycoming IO-360-C1C), best economy is peak EGT. You lean until the needle peaks. Best power is 100-150 deg ROP (rich of peak EGT). So, you lean until the EGT needle peaks, and then enrichen until the needle moves 4-6 divisions lower on the gauge (25 deg/division). BTW, I dumped my old gauge for an engine monitor. It's so much nicer dealing with actual numbers rather than that gauge - but I digress.

CHTs are much more important to worry about than EGT. CHT's are measured with a probe screwed directly into the cylinder head (or perhaps a ring at the base of the spark plug, but still in contact with the cylinder head). Therefore, the CHTs are a much more precise measurement. Engine manufacturer's give specific limits on CHTs, which should be observed at all times.

For my engine, the CHT's peak somewhere between best economy (peak EGT) and best power (150 deg ROP). Some people don't want to enrichen all the way to best power, because the fuel burn is so much higher (for me at 75% power it's a difference of 2 GPH). So they will go maybe 50 or 75 deg ROP. This can be a problem because this may well put them in a zone where the CHTs are peaking, or at least are much higher than at either best economy (peak EGT) or best power (150 ROP). In general, it is good to keep the CHTs lower, rather than higher. But no matter what, keep them within the range recommended by the engine manufacturer. (Someone showed me an old Lycoming manual for my engine from the early 70's where they recommended operating at 75 deg ROP, but they don't recommend that anymore - presumably because that setting yields higher CHTs.)

I guess my point is to get a copy of the operating manual for the engine if you don't have one, and follow Continental's instructions/procedures.
 
There is a reason a lot of EGT gauges don't actually have temperatures on them, The actual EGT temperature means very little. The relative temperature to Peak EGT is what matters.

Now if you get an engine monitor and monitor all the cylinders if one is way different than the others, there may be something to investigate, but even then maybe not.

Now CHT temperatures are a different story/lesson.

Brian
CFIIG/aSEL
 
On two different carbureted engines I've flown, with single EGT/CHT gauge, the engine runs rough as you lean and the EGT just keeps going up. Try and figure THAT out. You can't lean with an EGT very well with one gauge and carbureted. You need balanced fuel injection and CHT/EGT on every cylinder. So if your 182 is carbureted youre not going to gain much with full instrumentation.(you will just KNOW which cylinder is the one running the leanest, but so what?)

I just lean it as far as I can if I am running at 65% or less power and if I'm running at higher power I richen it up a bit. I lean all the way and richen 3 half turns at 5000 Density and higher. Then lean 1/5 of the way in for each 1000' lower so its full rich at sea level. Keep an eye on fuel flow, exhaust and spark plug color.

Without balanced injectors (GAMIS etc) and EGT on all cylinders, it's not an exact science.
 
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Worry less about EGT and pay more attention to CHT. EGT is likely measured from just one cylinder. And you do not have GAMI's.

You also didn't mention altitude, as that also affects the ability to lean.
 
I like to lean over 5000' by maintaining my takeoff EGTs as I climb...at twist or two leaner for every 1000 ft., keeping the mixture at least 150 degrees ROP for climb power and to avoid detonation (for my engine that means an average of 1250 F or so). Above 8000' density altitude, no matter what you do with a normally aspirated engine you're not making over 75 percent power (and avoiding detonation zone), so lean to roughness, then slightly enrichen for smooth running. I only bother with economy leaning over 8000' DA. Let your POH be the ultimate guide as to what you can/can't do.

As a general rule, if the CHTs are happy (sub 400 F), the engine is happy.
 
Bonchie said:
I'm new to a 182P and the POH says what I was always taught. Lean til rough, rich til smooth.
Click to expand...

If you keep reading, you should see that your POH has a blurb about how to use the optional EGT gauge.
 
SoCal RV Flyer said:
I like to lean over 5000' by maintaining my takeoff EGTs as I climb...at twist or two leaner for every 1000 ft., keeping the mixture at least 150 degrees ROP for climb power and to avoid detonation (for my engine that means an average of 1250 F or so). Above 8000' density altitude, no matter what you do with a normally aspirated engine you're not making over 75 percent power (and avoiding detonation zone), so lean to roughness, then slightly enrichen for smooth running. I only bother with economy leaning over 8000' DA. Let your POH be the ultimate guide as to what you can/can't do.

As a general rule, if the CHTs are happy (sub 400 F), the engine is happy.
Click to expand...

This works well if you take off on a standard day near sea level--it is called "Target EGT," and that umber can be safely used again and again.

Even works in my plane with a mixture lever in the quadrant, where the "twist" method does not apply.
 
The little star sounds like an Alcor EGT gauge. The temp value of that little star is adjustable and needs to be set by you to represent peak EGT for your normal flying conditions. It helps you get to whatever temp value you prefer to operate at. In no way does it represent 400*. I've never seen a star on a CHT gauge. Ideally you'd have a digital readout but old instruments use green and red range markings. You'd be well served to find out what the ranges really represent for temps. Don't assume it's accurate for a specific temperature. You can change senders and the range will change. In fact I used to sort through senders to get the gauge to operate where I wanted it. Digital gauges are a better solution.
 
Stewartb said:
The little star sounds like an Alcor EGT gauge. The temp value of that little star is adjustable and needs to be set by you to represent peak EGT for your normal flying conditions. It helps you get to whatever temp value you prefer to operate at. In no way does it represent 400*. I've never seen a star on a CHT gauge. Ideally you'd have a digital readout but old instruments use green and red range markings. You'd be well served to find out what the ranges really represent for temps. Don't assume it's accurate for a specific temperature. You can change senders and the range will change. In fact I used to sort through senders to get the gauge to operate where I wanted it. Digital gauges are a better solution.
Click to expand...

You are talking about the adjustable bar you set for peak EGT for future reference I think. The star is different.

Look at an Alcor EGT gauge. Count up 25 degree divisions until you get to what would be 400 degrees. There's a star on that line that's not adjustable.

46150.jpg
 
400* isn't a useful number for EGT.

You calibrate peak EGT to the asterisk using a little screwdriver. The needle is adjusted using the finger screw under the instrument face. That's just a quick visual reference tool for the pilot.

http://alcorinc.com/PDF/59185.pdf
 
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coloradobluesky said:
On two different carbureted engines I've flow, with single EGT/CHT gauge, the engine runs rough as you lean and the EGT just keeps going up. Try and figure THAT out. You can't lean with an EGT very well with one gauge and carbureted. You need balanced fuel injection and CHT/EGT on every cylinder. So if your 182 is carbureted youre not going to gain much with full instrumentation.(you will just KNOW which cylinder is the one running the leanest, but so what?)

I just lean it as far as I can if I am running at 65% or less power and if I'm running at higher power I richen it up a bit. I lean all the way and richen 3 half turns at 5000 Density and higher. Then lean 1/5 of the way in for each 1000' lower so its full rich at sea level. Keep an eye on fuel flow, exhaust and spark plug color.

Without balanced injectors (GAMIS etc) and EGT on all cylinders, it's not an exact science.
Click to expand...
One of your plugs is misfiring, and still burning in the exhaust stroke. That causes roughness and high EGT at the same time. Or, your timing is retarded.

It needs to be checked out.
 
Bonchie said:
You are talking about the adjustable bar you set for peak EGT for future reference I think. The star is different.

Look at an Alcor EGT gauge. Count up 25 degree divisions until you get to what would be 400 degrees. There's a star on that line that's not adjustable.

46150.jpg
Click to expand...
400 deg is an extremely low EGT. The markings can't mean what you think. Maybe 1400 deg.

400 deg is a common limitation for CHT.
 
MAKG1 said:
400 deg is an extremely low EGT. The markings can't mean what you think. Maybe 1400 deg.

400 deg is a common limitation for CHT.
Click to expand...

On this gauge, the temperature divisions do not add up to an actual temperature. I'm not confused about that. It's just a relative measure for leaning from peak EGT once seen. The gauge doesn't actually say "400" on it. But the 25 degree divisions add up to that amount, hence me referencing it to show what point I'm talking about on the gauge.

Stewartb said:
400* isn't a useful number for EGT.

You calibrate peak EGT to the asterisk using a little screwdriver. The needle is adjusted using the finger screw under the instrument face. That's just a quick visual reference tool for the pilot.

http://alcorinc.com/PDF/59185.pdf
Click to expand...

Thanks. It just clicked and I get it now. I didn't realize there was a separate screw under the thumbscrew that you adjust the peak EGT to match the asterisk with. Then the adjustable bar is set lower (50-75 degrees) as a reference for setting a safe ROP quickly.

So in that case, this gauge isn't actually warning of any dangerous temperature over a certain mark. Makes sense.
 
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