JPI 700 - Lean of Peak

Beachcomber

Beachcomber

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Beachcomber
Just purchased an aircraft that has the JPI 700. The IO-540 has GAMI injectors so I can run lean of peak. Prior to purchasing this airplane, all the others I’ve flown, I’ve never been disciplined before about leaning. I’d just always pull the mixture back until it started to run rough, and then give it a few twists on the rich side.

I’m learning that’s not how to lean, especially if you have engine instrumentations that help you lean most effectively. So my new plane has the JPI 700 and I’ve read the manuals and watched the videos. I’m still not sure how to really lean this engine effectively lean of peak.

Does anyone know how best to lean it or have written instructions available? I’ve read to stay out of the ‘red box’....so clearly my old way of leaning would not be a good idea here.

What used to be something so simple to me, now seems a bit complex.
 
Tap LF button. It should say LOP. If it says ROP, hold both buttons in about three seconds until it switches to LOP. Start leaning the mixture until you get LEANEST, that will tell you the cylinder than peaked first. Keep leaning until you get RICHEST. This will be the last peaked cylinder. The thing will now be displaying a negative number which is how far LOP you are (in degrees). You can tweak the mixture to get what you want.

As long as you do this at some sane cruise setting (65-75% power), you won't have any red zone problems for the brief time you're doing this operation.
 
Download the JPI 700 pilots guide from the internet and go to page 16. It will explain.
My IO-540 with GAMI’s can be leaned to 10.5 gph, but I lose about 5 knots of true airspeed. I do very long cross countries and save a lot of gallons.
 
When leaning, note the fuel flow for peak EGT at your selected MP and RPM. Next, note fuel flows at some target LOP operating points (20, 50, xx degrees LOP). In the future you can set rpm and MP then make the big mixture pull to a selected fuel flow. Some guys leave the throttle wide open and just use mixture to set power at a selected RPM. I’d prolly want to be above 5,000 ft so engine power would be below 80%.
 
Oh, by the way, an STC'd install of the unit almost certainly requires the flight manual supplement AND the pilot's guide be in the plane.
 
flyingron said:
Tap LF button. It should say LOP. If it says ROP, hold both buttons in about three seconds until it switches to LOP. Start leaning the mixture until you get LEANEST, that will tell you the cylinder than peaked first. Keep leaning until you get RICHEST. This will be the last peaked cylinder. The thing will now be displaying a negative number which is how far LOP you are (in degrees). You can tweak the mixture to get what you want.

As long as you do this at some sane cruise setting (65-75% power), you won't have any red zone problems for the brief time you're doing this operation.
Click to expand...

This is perfect, can’t thank you enough for this write up. Will give it a shot on Saturday. Thanks again.
 
You know you are lean of peak when you lean the engine and it gets cooler.
 
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