Leaning the SR 22

[Fly_Unity]

I'm flying a brand new cirrus SR22 Turbo w/garmin perspective. I was taught by UND (at Duluth) to lean using lean of peak, by pulling mixture till arrows match up. However on the 100 hour inspection, the mechanic recommended that I use the rich of peak technique to save on wear. Is there a way I can set the garmin so the arrows are set to Rich of peak?

Also how much cooler of Lean of Peak are you guys running it?

 

[Roger, Roger]

John Deakin of Avweb has a lot of good columns on mixture management.
Also, your mechanic is just saying what is taught in just about every maintenance school out there-that running your engine lean of peak will ruin it. I know because I went through A&P school and that's what they taught. There's plenty of evidence that that is not the case.

 

[USMCmech]

Your mechanic hasn't kept current with modern research and operating pratices, and is relying on information passed down from the 1950s.

LOP is has no effect whatsoever on mechanical wear of the engine. This applys not only to Ciruss, but all piston engines as well.

 

[Fly_Unity]

Ok, I been continuing to fly LOP, however every hour or so I feel the engine like misfire, or detonate. If I turn one (either) mag off the engine runs really rough and detonates pretty bad instantly. CHT's and EGT's are all in the normal limits.

When I'm running ROP, I never noticed detonation, and when I cycle the mags (rich of peak), The engine runs perfectly fine on either mag.

Is this normal? I talked to different mechanics, and they are all against cruising using LOP.

(btw I always ran with full rich mixture in a climb in the Turbo Charged Model)

 

[Roger, Roger]

How do you know that it's detonating instead of just running rough?

Maybe get the mags and ignition harnesses looked at? Running at high altitude is pretty rough on them, and a lot of times a misfire will only show up at altitude.

 

[USMCmech]

Ok, I been continuing to fly LOP, however every hour or so I feel the engine like misfire, or detonate. If I turn one (either) mag off the engine runs really rough and detonates pretty bad instantly. CHT's and EGT's are all in the normal limits. When I'm running ROP, I never noticed detonation, and when I cycle the mags (rich of peak), The engine runs perfectly fine on either mag.

When running LOP what you are feeling is NOT detonation, but rather a mismatch of power from the different cylinders. Your engine obviously does not have a very well matched set of fuel injectors.

When running LOP, Hp drops dramaticly as you reduce fuel flow. If you look closely at the EGT as you lean past peak, you will see that each cylinder hits peak at a different time. This means that instead of you 300Hp/6cylinder engine puting 50 Hp per cylinder, you are getting 45 from some, and 40 or 50 from some others. This results in the vibration you are seeing.

Get a set of GAMIjectors ASAP and you will see a vast improvement.


Climbing full rich is very wise, keep doing that.

 

[Fly_Unity]

How do you know that it's detonating instead of just running rough?

Maybe get the mags and ignition harnesses looked at? Running at high altitude is pretty rough on them, and a lot of times a misfire will only show up at altitude.

I dont think its High Altitude misfire because the combustion chamber as well as the magnetos and sparkplugs are pressurized in this plane through the turbo system

 

[Fly_Unity]

When running LOP what you are feeling is NOT detonation, but rather a mismatch of power from the different cylinders. Your engine obviously does not have a very well matched set of fuel injectors.

When running LOP, Hp drops dramaticly as you reduce fuel flow. If you look closely at the EGT as you lean past peak, you will see that each cylinder hits peak at a different time. This means that instead of you 300Hp/6cylinder engine puting 50 Hp per cylinder, you are getting 45 from some, and 40 or 50 from some others. This results in the vibration you are seeing.

Get a set of GAMIjectors ASAP and you will see a vast improvement.


Climbing full rich is very wise, keep doing that.

Its not a "vibration" Im feeling, its a sudden jolt through the airframe that only happens once an hour or so. (the instant I run it on either mag it happens every other second or so, AND the engine runs very rough)

This does not happen when Im running it rich of peak. running it on either mag has no noticeable affect.

So is what happening here normal? is it still a good idea to run LOP?

I'll have to check into the GamIjectors. Know off hand how expensive this is?

 

[Blip16]

we always leaned the SR20 at UND main campus by using the Lean Assist. doesn't Garmin have something like that?

 

[Fly_Unity]

we always leaned the SR20 at UND main campus by using the Lean Assist. doesn't Garmin have something like that?

Garmin does have Lean assist, did you run Lean of peak or Rich of Peak? The new Garmin 1000 Perspective you just pull the mixture handle back till the arrows match up with each other, which sets it to LOP. To set ROP you have to use the Lean Assist

 

[Blip16]

Garmin does have Lean assist, did you run Lean of peak or Rich of Peak? The new Garmin 1000 Perspective you just pull the mixture handle back till the arrows match up with each other, which sets it to LOP. To set ROP you have to use the Lean Assist

the Avidyne setup lets you do both i think. Well Best economy (so just peak) and then Best Power (ROP)

 

[ppragman]

I'm flying a brand new cirrus SR22 Turbo w/garmin perspective. I was taught by UND (at Duluth) to lean using lean of peak, by pulling mixture till arrows match up. However on the 100 hour inspection, the mechanic recommended that I use the rich of peak technique to save on wear. Is there a way I can set the garmin so the arrows are set to Rich of peak?

Also how much cooler of Lean of Peak are you guys running it?

If you can, find what the thing does at sea level with fuel burn, then lean to that. I've heard both sides of the story, and I trust my mechanic, and try not to run it LOP. We did an experiment at my old company where on only one airplane, everyone ran it LOP, and the motor missed TBO by 400hrs. I hear the same thing everytime I lean as well, I try not to.