Cirrus SR-20 lean assist

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Stets656

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Ben
Wondering how to properly use the lean assist in a Cirrus SR-20 with IO-360-ES. It has the avidyne R-9 package. I do know that once you press start lean assist you can begin pulling the mixture and you can see the peaks of the cylinder's EGTs once they indicate blue. Now the cirrus POH says to set the EGT to 75 degrees rich of peak to achieve best power. The question I have is, once the cylinders start to peak and turn blue the EGT temp turns to a blue color and turns negative. What does this mean and how do you tell that the EGTs are 75 rich of peak?? Thanks!
 
Stets656 said:
Wondering how to properly use the lean assist in a Cirrus SR-20 with IO-360-ES. It has the avidyne R-9 package. I do know that once you press start lean assist you can begin pulling the mixture and you can see the peaks of the cylinder's EGTs once they indicate blue. Now the cirrus POH says to set the EGT to 75 degrees rich of peak to achieve best power. The question I have is, once the cylinders start to peak and turn blue the EGT temp turns to a blue color and turns negative. What does this mean and how do you tell that the EGTs are 75 rich of peak?? Thanks!
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Peak means that the EGTs are at the highest temperature. "75 rich of peak" means that you enrichen the mixture until the egts are 75 degrees cooler (minus) than peak. So when peak is indicated, you enrichen the mixture slowly until you see -75 degrees on the indicator. Within a few degrees is generally good enough.
 
3 - 2 - 1 -


(I'll post for the naysayers)

Oh no, here's another one of these Mike Busch deals...

His data is bla bla bla...

Cirrus owners jump on his bandwagon and he's getting rich...

Don't believe the data...

I don't own a cirri and I don't buy his services but I like what he has to say.
 
PaulS said:
Peak means that the EGTs are at the highest temperature. "75 rich of peak" means that you enrichen the mixture until the egts are 75 degrees cooler (minus) than peak. So when peak is indicated, you enrichen the mixture slowly until you see -75 degrees on the indicator. Within a few degrees is generally good enough.
Click to expand...

So should I be waiting for all the cylinders EGTs to peak? Or should I enrichen the mixture after detecting the 1st peak? I believe the EGT turns to blue and negative after the first cylinder peaks. I was also told by a CFI that if I set the mixture lean of peak then I will burn a whole in the exhaust because the engine will be so hot.
 
Stets656 said:
So should I be waiting for all the cylinders EGTs to peak? Or should I enrichen the mixture after detecting the 1st peak? I believe the EGT turns to blue and negative after the first cylinder peaks. I was also told by a CFI that if I set the mixture lean of peak then I will burn a whole in the exhaust because the engine will be so hot.
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Watch the video and make your decision after. I never lean to a peak. The philosophy will be explained.
 
So doesn't it actually give you a display that says "Best Economy" 30 degrees after the last cylinder goes LOP?
That is the plane telling "You done good boy!"

LOP would be after the last cylinder goes past peak.
 
And to answer your question 75 degrees rich is "Best Power".
When you see them go negative, you have past peak on that cylinder and now are on the lean side.
Keep leaning for "Best Economy" and that won't be -75 degrees. I suspect if you get to -75 it will get really quiet in the plane.
 
Stets656 said:
So should I be waiting for all the cylinders EGTs to peak? Or should I enrichen the mixture after detecting the 1st peak? I believe the EGT turns to blue and negative after the first cylinder peaks. I was also told by a CFI that if I set the mixture lean of peak then I will burn a whole in the exhaust because the engine will be so hot.
Click to expand...

Not sure of your set up or year, but I would go by the poh. Typically with the perspective lean assist for rich of peak, you set power to what you want, typically 75%, fuel boost off, unless you need it for vapor suppression ( really hot day). Cirrus recommends pulling until the first cylinder hits peak, then enrichen until -75 degrees. That's it. For lean of peak, set the power to about 67%, lean until the last cylinder is at peak, then keep leaning until -50 degrees. And that's it for LOP. Cirrus doesn't want the engine run above 65% power, LOP, you'll see the power decrease as lean, that's why you start a little higher. These numbers assume you are running the Continental engine, which it looks like you are.

As others have mentioned, you don't want to be at peak for very long, that's where you can have problems. Leaning is like religion, there are a lot of different opinions out there. I rent, so I run the way the owners want it run, which is per the poh.

On Cirrus approach, they have some pretty good videos on this stuff. You have to buy them, but worth the money.

Time wise, rop doesn't really buy you that much on shorter trips, and lop will save a lot of gas. When you rent wet, it doesn't matter that much though.
 
PaulS said:
Typically with the perspective lean assist for rich of peak, you set power to what you want, typically 75%, fuel boost off, unless you need it for vapor suppression ( really hot day). Cirrus recommends pulling until the first cylinder hits peak, then enrichen until -75 degrees.
Click to expand...

yes this is what I was asking. I was unsure if I should get all of the cylinders to peak or just the first one before enriching again. I don't believe the POH specified one way or another but I could have missed it.
 
Stets656 said:
yes this is what I was asking. I was unsure if I should get all of the cylinders to peak or just the first one before enriching again. I don't believe the POH specified one way or another but I could have missed it.
Click to expand...

The video I mentioned shows this method. Also that engine has an altitude compensating fuel pump, so you may not be able to get to 75 rop. Just something to keep in mind.
 
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