how to properly lean a carb engine

[Mooneyjet]

Hey guys, i dont have much experience with carb operated engines and i would like to know how to properly lean an engine, any tips and instruction in how to properly do it. thanks

[eldeano]

Wow, Thank god you are not fuel injected! If you only new what a can of worms you just opened!!  Do you have an engine anylizer?  Generally, you would lean to about 100 degrees rich of peak.  At altitude, after about 8000 ft or so you will no longer be at full power, you can then lean to about peak.  Basically, lean until the engine runs rough, then give about three turns in.  Don't know what kind of equipment you have, but will assume you are running around 24/24.

Let the posts begin!!!!

[GeorgePerry]

Quote: Mooneyjet

Hey guys, i dont have much experience with carb operated engines and i would like to know how to properly lean an engine, any tips and instruction in how to properly do it. thanks

[eldeano]

Quote: GeorgePerry

No EGT guage...lean until rough, then three full twists toward rich. 

W/ an EGT guage lean until peak then enrichen to 100 deg rich of peak if at 70-75% power.  65% or less, 50 deg ROP for best power and peak EGT for best economy.

[Mooneyjet]

Thanks for the replys, i got a digital egt/cht, with the airplane, it just seems to be burning more fuel than what i planned for fu, between 11 to 12 gph @ 6000 feet running about 24mp and 2500 rpm.

[lahso]

Mooneyjet, not sure what model you have, but in my C I use WOT/2400 RPM at 6/7,000 feet (usually 22"). I use my EDM700 to get the hottest cylinder EGT around 1400. This gives me 10 GPH.

[Mooneyjet]

The mooney that i'm picking up is a c model, with a Lycoming O-360-A1A, so do you run your egt at about 1400.

[lahso]

Quote: Mooneyjet

...so do you run your egt at about 1400.

[Shadrach]

Quote: GeorgePerry

No EGT guage...lean until rough, then three full twists toward rich. 

W/ an EGT guage lean until peak then enrichen to 100 deg rich of peak if at 70-75% power.  65% or less, 50 deg ROP for best power and peak EGT for best economy.

[Z W]

1500 EGT gives me about 380 on the cylinder temps and I believe is closer to max economy than the numbers described by Iahso.  At those same MP/RPM settings that will do around 9 GPH instead of his 10.  Either setting works just fine, his probably gives a little more power but less economy.  If you don't have a full EDM to show the cylinder temps you may want to stick with the richer setting, to make sure you arent cruising around at 400+ dF on the cylinders.

[Shadrach]

Quote: Zane

1500 EGT gives me about 380 on the cylinder temps and I believe is closer to max economy than the numbers described by Iahso.  At those same MP/RPM settings that will do around 9 GPH instead of his 10.  Either setting works just fine, his probably gives a little more power but less economy.  If you don't have a full EDM to show the cylinder temps you may want to stick with the richer setting, to make sure you arent cruising around at 400+ dF on the cylinders.

[Hank]

Mooneyjet--

I lean my C to find peak [often 1500-1525ºF] then enrichen. Play with the Performance Tables and find some "standard" settings; I copied them and carry them on my kneeboard to preserve the fragile, brown 40+year-old pamphlet titled "Owner's Manual."

Two twists or three on the mixture is something I cannot help with, as I have levers on a quadrant. I just watch the EGT needle move.

Low level I often run 23/23; around 5000 msl I run 22/2400; starting about 7500 I begin running 2500. Once WOT gives suitable power settings, I back the throttle off until the MP needle starts to move [around 10,000 msl this can be almost 1/3 travel] to give better atomization and mixing coming through the carb. Overall, I average 135-140 kts [125-135 MPH indicated] and very close to 9 gph. Highest sustained level cruise 183 kts; lowest sustained level cruise 105 kts. East is often faster than west, and I fly more N-S than anything with prevailing crosswinds.

Enjoy your new ride! Fly lots, have fun, take notes on how she does for future reference as you learn her quirks.

[Z W]

Quote: Shadrach

[Z W]

That's 2400-2500 RPM, WOT, 7k-9k feet, in a carbeurated C model, like the other posts have been talking about flying. Can't get this to show in the post above for some reason.

[Shadrach]

Zane, that's really not useful interms of context. EGT values are only useful relative to peak. TIT values are only really useful relative to peak and TIT redline. Other than that, nada, zilch, zero... Different set ups and instalations yeild different raw numbers on EGTs and even TIT, but that's the best we've got in that case.  Two M20Js (insert whatever type here) from the same year, with the same type engine, with the same hours and the same brand and type instrumentation could and likely would generate different raw number even if flown at the exact same power setting side by side at the same alt...

[danb35]

Quote: Zane

That's 2400-2500 RPM, WOT, 7k-9k feet, in a carbeurated C model, like the other posts have been talking about flying. Can't get this to show in the post above for some reason.

[lahso]

Dan and Ross make a good point - my aircraft is different than yours, and I consulted my A&P on his recommendations for engine performance based on its equipment and his experience with the plane. My numbers work for me, but yours may vary slightly.

[jetdriven]

If our A&P is not a licensed pilot and is telling you to lean to an EGT number, I would take that with caution. 

FWIW our peak EGT at 20 degrees of timing was 1585.  At 25 degrees timing its like 1510.

[Hank]

FWIW, my carbed C model usually peaks [on my EGT] between 1500 and 1525, depending on conditions.

Unlike you guys in E, F and J models, our carbs often do not perform well LOP. Thus the bit about back off on throttle enough to move the MP needle. Depending on how I feel and how high I'm flying, sometimes I will lean to peak then richen up, sometimes I will lean to rough and richen up. When my wife is with me, I don't even need to watch the needle, SHE is my rough alert!

Sometime soon I plan to make the normal weekend run one way at 23/2300 and back at 22/2400 [almost always at 3000 msl] and see if there is any difference. I'll record IAS, GS and actual fuel burn at the pump [one tank each way, usually 8 gals roundtrip]. Leaning will be the same-old same-old. If the rain holds off, maybe this weekend?

[jetdriven]

Some 182 guys mix a touch of carb heat with the slightly cocked throttle trick.  In some cased, they can run just LOP smoothly.  I'd guess if you run it at the edge of smooth above 5000' you cannot hurt it.  Might save a few gallons.  Your plane talks to you.  Ours speaks French.

[Ned Gravel]

Quote: Hank

FWIW, my carbed C model usually peaks [on my EGT] between 1500 and 1525, depending on conditions.

Unlike you guys in E, F and J models, our carbs often do not perform well LOP. Thus the bit about back off on throttle enough to move the MP needle. .......

[Hank]

And now you know why "everyone" says that the actual peak temperatures are irrelevant. The important thing is where you operate in relation to your peak, and with a E, which way you move the red knob/lever to get there. For me, 1450 if often a good spot, for you, maybe not so much. To each his own.

Another wrench to throw in is that I only have the single factory probe, while others here have multi-cylinder probes. Even then, they often use the factory probe on one cylinder, so that one reads different from the others. "Degrees Rich/Lean of Peak" is important, your actual displayed peak temperature not very much at all.

Ain't life great?

[Shadrach]

My cylinders peak anywhere from 1580 to 1430df depending on which one, MP and RPM... What does that tell anyone? 

[Ned Gravel]

Quote: Shadrach

My cylinders peak anywhere from 1580 to 1430df depending on which one, MP and RPM... What does that tell anyone? 

[Shadrach]

ding ding ding!