Leaning (redux)

[chrixxer]

Is this article good info?

Is this ($400 online) course a good way of learning how to properly lean?

Have a '69 M20F, IO-360-A1A, with an EDM-700 engine monitor, FS-450 fuel totalizer, and other goodies (including cowl closure and oil cooler relocation mods). Also has a scimitar prop with "continuous operations between 2350-2550 rpm above 24" MP prohibited" placard. Still getting a feel for how to configure her in cruise, for maximum speed and/or efficiency. But at least now I have the information in the cockpit to do it (vs. single probe E-1 EGT and a fifty-one year old Garwin CHT gauge).

Looks like a lot of my flying will be in the 6500-8500 range (just not quite long enough of a trip to climb to 10,000+), and if "2500 RPM and WOT" is decent advice, I will usually be above 65% power if I follow it, so I worry about leaning into the Red Box of Profound Engine Unhappiness... Would love to find some Mooney (especially "Vintage" Mooney) specific engine operation education... Is leaning into 1500°+ EGT normal? (CHTs stayed well south of 400°.) On a 10°C OAT, 7500', 30.14" Hg day, what's a reasonable peak EGT to see? (Can the EDM-700 Lean Find work for CHT, or just EGT? Looks like just EGT, though Busch recommends using CHT...) Questions, questions, so many questions...

[KSMooniac]

That course is the best education you can buy as an owner/operator. Only thing better is the live course in person.

The principals are suing each other, unfortunately, so the live courses are suspended now. If you can still take the online version you should do it, and soon.

Sent from my LG-US996 using Tapatalk

[chrixxer]

24 minutes ago, KSMooniac said:

That course is the best education you can buy as an owner/operator. Only thing better is the live course in person.

The principals are suing each other, unfortunately, so the live courses are suspended now. If you can still take the online version you should do it, and soon.

Sent from my LG-US996 using Tapatalk
 

Copy that, thanks. Yeah, I saw that the live course had no future dates.

[Hank]

Lean until EGT peaks, then either lean more or richen up. The exact number doesn't matter, many older planes don't even have numbers on their EGT gage. Why? Because if yours is installed 1/2" closer or further away than mine, our EGT numbers will be rather different. 

So find your peak and go from there.

[BigD]

44 minutes ago, David Herman said:

 

Cruise, (usually 9000’-11000’) for the carbureted C,

        I reduce the throttle until I see the MP reduce slightly (this closes an enrichment circuit in the carburetor, not found in your injected F) so I’m basically WOT (less closing the enrichment circuit)  (the MP is anywhere for about 19.5 - 22.0 depending on the altitude) 

 

 

 

 

Just curious about enrichment circuit. I left my throttle full at 11,000 with prop at 2400 in cruise. I was getting about 8.8 gph. My temps were always below 400/1400 (cht/egt)... should I be pulling back Mp? At 11,500 my Mp was already pretty low. Thanks. 

[carusoam]

24 minutes ago, BigD said:

Just curious about enrichment circuit. I left my throttle full at 11,000 with prop at 2400 in cruise. I was getting about 8.8 gph. My temps were always below 400/1400 (cht/egt)... should I be pulling back Mp? At 11,500 my Mp was already pretty low. Thanks. 

Your carb has an enrichment circuit.  You can see it’s linked operation under the cowl.  It is only open at full throttle... (on the ground)

Pulling back the throttle to see a small amount of MP wiggle is all it should take... (in the air)

@Hank has the best description for how he handles it...

There are a few drawings for the M+S carburetor posted around here.  The entire manual section for Mooney is about 2.5 pages long with drawings...  worthy of a good read...

Best regards,

-a-

[Hank]

Wow, I feel so appreciated!

In my C, I climb WOT/2700/Full Rich as high as I'm gonnna go (which may be an ATC intermediate clearance). When I remember, I lean using the Target EGT method. Let her accelerate, and if I'm high enough per my Performance Tables, I pull the throttle until the MP needle wiggles, set RPM (generally 2500, but may be 2400 below ~7500msl), and lean away.

But none of this applies to your F--since you don't have a carburetor, there's no enrichment circuit to shut off (it supplies extra fuel for cooling when running WOT). Many people fly their injected Mooneys LOP per the instruction from Ada, OK. Leave the throttle at WOT, set desired RPM, and do the Big Pull to get on the lean side of Peak EGT. But leanness is measured from the last cylinder to reach peak, so that all cylinders will be on the lean side when you're done.

Wish I could help with fuel flow data, but I'm not yet instrumented for that. When trying to fly a carbed engine LOP, try these:

• Reduce throttle to shut off the enrichment circuit. This leaves the throttle plate less than wide open inside the carb, with the goal of creating turbulent flow through it. The turbulence will break up the fuel into smaller droplets, and mix the fuel more thoroughly into the air in hope of a more even distribution of fuel between all cylinders. 
• Add partial carb heat, which will warm the air up some, richening the mixture. This allows further leaning. Also, the warmer air, being slightly less dense, may be more turbulent and will certainly be easier to mix up.

Even with this, my C would not run smoothly much below peak, judging by the 25°F increments on my EGT. But I spent two annuals resurrecting my doghouse, and now I can run smoothly almost 25°F LOP without using any carb heat. So it's possible. But it's also slow, i think I lose around 10 mph indicated, so it's not something I use often or for travel. I generally run 50°F ROP, turning in ~148KTAS with 9 gph fuel burn measured fuel pump to fuel pump divided by flight time. There's about a 25° variation in my Peak EGT value depending on OAT and altitude, another reason to ignore the actual number. 

Descents are simple, push the yoke for 500 fpm, trim away the forces and come down at 170mph indicated. As I descend, MP increases and the mixture leans out, increasing EGT, so I periodically reduce throttle and richen mixture to regain my cruise values of MP and EGT. Then start slowing down a couple of miles from my destination and enter the pattern as close to 90mph with Takeoff Flaps down as I can; sometimes I don't get the flaps down until downwind as I'm still above 125mph. 

Fly safe, ya'll!

[Hank]

If only I could figure out how to write short posts . . . . .  

[carusoam]

David,

Expect that there isn’t any automation on the enrichment...  

Full throttle opens it up.  Where this happens and un-happens is an adjustable mechanical link.

 

Looking at it from a logic point of view... there are four sources of fuel flow in the carb...

• Accelerator pump
• idle flow, 1-3 gph
• The primary fuel jet, 0-18gph
• Enrichment jet, 2-3 gph

Take a look at the carb drawing to see where these flows come in...

Throw On the use of mixture control... you might not see the enrichment jet working even with the best FF instrumentation...

Unless you are really looking for it...   

My C had no extra instrumentation... No FF or JPI or carb temp...

Leaning was done with the single EGT, without direct temperature calibration...

With FF, and a JPI, It would be interesting to see if the EGTs improve or get worse with the enrichment jet operating...

Best regards,

-a-