Lean of Peak

[BradG]

Ok, so whats the opinion on running an engine "Lean of Peak"? Specifically, a stock 300hp Lycoming IO-540. Is it good for the engine? I have run lean of peak once, and i noticed that the temps were ok, and the fuel flow was pretty low. Im looking for pros, cons, and tips.

Thanks,

Brad

 

[jrav8tor]

Brad,

Check this articles written by John Deakin from AvWeb. They are real informative and go against the grain of many myths.

http://www.avweb.com/articles/pelperch/perchlinks.html

Hope this helps!

jrav8tor

 

[avbug]

Brad,

Temperatures lean of peak will always be cooler than running at peak, just as running rich of peak works the same. The risk of running lean of peak is detonation at higher power settings. You need to consider manufacturer recommendations prior to selecting a setting at which to run the engine.

The 520 tends to be a robust engine, but isn't tolerant of high temperatures, and like any engine, isn't tolerant of detonation, either.

What practices are you using for setting the mixture, what monitoring equipment do you have, and what is your experience with the engine? Are you familiar with the manufacturer literature and publications for that engine (not just the aircraft manufacturer; the engine manufacturer. Hint: it's not in the AFM)?

 

[ChinaClipper]

careful

Not a good idea unless you have a fuel injected engine, read up on GAMI injectors. Unless you have a DC-7 or Constellation with a prt R-3350! then its standard practice with a good flight engineer!

 

[Timebuilder]

One of the great things about the internet is to have access to guys like Avbug and Deakin.

As much as I enjoy our discussions of unions, "regional" jets, and flight schools, I try to learn something every day.

Thanks.

 

[TDTURBO]

Brad,
The 520 tends to be a robust engine, but isn't tolerant of high temperatures, and like any engine, isn't tolerant of detonation, either.

Are you familiar with the manufacturer literature and publications for that engine (not just the aircraft manufacturer; the engine manufacturer. Hint: it's not in the AFM)?

AVBUG,

A Lycoming 520 is a robust engine indeed, so robust they don't even need to make parts for them.

I couldn't help it avbug, you did the same thing to me when I did the same thing awhile back.

Like someone said earlier, read Deakin for a start, but running LOP with a non-fuel injected engine is impossible so if you’re thinking about doing it you obviously have FI. It's a great way to conserve gas and increase time between cylinder overhauls by keeping temps in check. Use a JPI or insight, both will do the job for the same price.

As AVBUG states, reading the manufacurers recommendations will aid in your quest for truth in proper engine management.

ELContre.........The engine manufacturers are at odds with one another, they have exact diametrically opposed philosophies with regards to engine management. It seems Lycoming and Continental can't agree on these "very” pressing"' issues.,

So if I were you, I would make sure I have fuel injection, if you don't then run 100-125ROP, sure you'll burn more gas and foul more plugs. With 300hp running out of a 540, it will be "taxed" to its limits and does not have as much room for error. These engines, especially the turbo'ed ones" can very temperamental and easy to break! AS IN DETONATION! You can solve that problem by running higher-octane gas additives or running a Prism electronic package to alter the timing. Some of the above mention strategies have STC's and some do not.


I ran a 540 to 2300 hrs and it still runs fine i.e.; perfect compressions, oil analysis ect......If you take care of your engine, lean it on taxi, start it up initially past 1200 rpm to get the oil splashed into the top end and begin taxi, your half way .there

Getting up into the air requires the same diligence, full throttle to you attitude, back off for cruise, lean to peak the richen it until you see a 3-4 bar graph drop. Decent is just the opposite, enrichen(maybe, if at all), close cowl flaps and watch your carb ice gauge.

I probably missed some impotent things but it's late and I'M TIRED!

Just READ DEAKEN IF YOU HAVE GAMIS OR FI or do what’s above, I Do and it's worked for me.

AND BY ALL MEANS………….FLY EVERY OTHER DAY!!!!! That’s the most important thing you can do!

 

[avbug]

TDTurbo,

Okay, it's a Wright 520. Hows that? Stupidity and lack of awareness aren't my best qualities, but they still stand out...

On the subject of fuel injection versus carburetion, there is no difference between the two when running lean of peak. At first blush, it may appear that the fuel distribution is the same to each cylinder in an injected engine, therefore making your chances of seeing an even mixture in each cylinder better. However, it's not the case. While the fuel flow divider may distribute the same amount of fuel to each cylinder, and you may even have specific injectors for each cylinder, you must still account for induction irregularities and inbalances.

The same amount of fuel may reach each cylinder, but not necessarily the same mixture is entering the combustion chamber. Also, each chamber doesn't receive the same spark, and volumetric differences will exist which aren't accounted for with injection.

You can run lean of peak in a carbureted engine. You can run lean of peak in a fuel injected engine, too. The engine doesn't know the difference. Until approaching a detonation range, generally at higher power settings or higher compression situations, lean of peak is the same as running rich of peak with respect to temperatures. It works the same on carbureted engines as fuel injected.

 

[tdvalve]

Don't remember the leaning procedure for anything except the 3350, but I think all large radials are run lean of peak. We always ran 3350's (with and without fuel injection) lean of peak in cruise. To not do so would have greatly reduced range. As I remember the procedure, it was: Set the desired RPM and BMEP or torque setting, lean to best power (peak), reset the throttles to the original BMEP/Torque setting, continue leaning until the BMEP/Torque dropped 10%, then reset the throttles to the original BMEP/Torque setting. I have heard of operators leaning as much as 18% below peak BMEP/Torque.

 

[A Squared]

Avbug,

>>>> While the fuel flow divider may distribute the same amount of fuel to each cylinder, and you may even have specific injectors for each cylinder, you must still account for induction irregularities and inbalances.

>>>>You can run lean of peak in a carbureted engine.

Yes, theoretically. In practice though, many ga engines equipped with a float type carburator have such poor induction systems that one cylinder may be leaned out to the point that it will no longer fire while other cylinders are still running slightly rich of peak.

Yeah, that's what the GAMIjectors attempt to do is to match the fuel flow for each cylinder to the air flow for that cylinder, thus making the Fuel/ air ration more nearly equal for all cylinders. I understand that GAMI will work with you in selecting a custome set of injectors, if for some reason your particular engine doesn't get equal fuel/air ratios with their injector set for your engine.

TD valve,

we use a simplified version of that on the R2800's

we just set cruise power, wait 5 minutes for the temperatures to stabilize, then lean. we lean to peak power, as noted on the BMEP gauge, then continue leaning until BMEP has dropped 12 psi below peak. Our engines don't have spark advance, so we obviously con't fool around with that.

regards

 

[Rvrrat]

The same amount of fuel may reach each cylinder, but not necessarily the same mixture is entering the combustion chamber. Also, each chamber doesn't receive the same spark, and volumetric differences will exist which aren't accounted for with injection.

Which brings up FADEC; a topic for a different thread perhaps.