The “Red Box”

[jakearey]

62C - O-360 engine 

Hey guys. New Mooney owner here with about 30 hours in the bird so far. I’m getting some standard power settings figured out, depending on how far I am traveling.  I am working on becoming more exact with my leaning. I currently have an EGT gauge that is nothing special.  What I am curious about is the best way to lean this engine? 
 

The EGT gauge was set by the IA/AP. This gauge only has one needle and has an asterisk that is supposed to be set to peak.  I generally will lean to the asterisk but the engine doesn’t roughen up any at the asterisk.  
 

Should I forget the asterisk and just lean until I feel a stumble in the engine, note that setting on the gauge and then richen a few notches on the gauge?   I have just been leaning to the asterisk, as taught, but lately I have read about this red box and became concerned that I am operating the engine incorrectly. 
 

I ultimately want to get an engine monitor and that will be my next mod but I don’t currently have one.   
 

And the concern is above 65% power, right?  Can someone help explain the red box and also share their leaning procedure for the C, please? 
 

thanks! 
JA 

[jakearey]

[EricJ]

The asterisk doesn't really mean anything.   You have a relative EGT gauge, and it'll say on it how many degrees per graduation, but it is not calibrated to values.   You find peak and make relative adjustments from there, i.e., richen it up however many degrees you want to run it.

 

[jakearey]

Just now, EricJ said:

The asterisk doesn't really mean anything.   You have a relative EGT gauge, and it'll say on it how many degrees per graduation, but it is not calibrated to values.   You find peak and make relative adjustments from there, i.e., richen it up however many degrees you want to run it.

 

Right, I appreciate that.  The gauge is supposedly set to be at peak on this aircraft when it was calibrated at OH recently.  
 

And to find peak, the best way is to just lean until a stumble is noticed, correct? 

[EricJ]

Just now, jakearey said:

Right, I appreciate that.  The gauge is supposedly set to be at peak on this aircraft when it was calibrated at OH recently.  
 

And to find peak, the best way is to just lean until a stumble is noticed, correct? 

On a carbureted engine, yes.    Peak can move depending on conditions, it may not always be at the same place on the gauge.

[Hank]

Just now, EricJ said:

The asterisk doesn't really mean anything.   You have a relative EGT gauge, and it'll say on it how many degrees per graduation, but it is not calibrated to values.   You find peak and make relative adjustments from there, i.e., richen it up however many degrees you want to run it.

 

This. The asterisk just makes it easier to remember where it reached peak. The EGT in my C has numbers, which makes it even easier.

Search around here, there are many threads on setting power in C models, with some pretty good explanations. If that doesn't work, type your search into google and add MooneySpace to it.

Many people with IO engines prefer to run Lean of Peak, but it's rather difficult to do with a carb. So I make sure Im below 75%then lean to 50°F ROP. Confirm in your manual, but the EGT marks are often 25° apart. Happy flying!

Oh, a good hint:  the numbers on your Manifold Pressure and tach should add to 47 or less, then you can't hurt anything with the mixture knob. 

[DXB]

1) Should I forget the asterisk and just lean until I feel a stumble in the engine, note that setting on the gauge and then richen a few notches on the gauge?   

YES!! Or if you have fuel flow, just use that instead of the EGT gauge. You'll find it more reliable.

2)I ultimately want to get an engine monitor and that will be my next mod but I don’t currently have one.   

Definitely do that - it is a terrific diagnostic tool and safety feature...sadly on a carb'd bird it doesn't help leaning much more than the lean to rough/rich to smooth method.

3) And the concern is above 65% power, right?  Can someone help explain the red box and also share their leaning procedure for the C, please? 

Mike Busch's EAA seminars and books explain in some detail.  Bottom line on the 180hp O-360 is that you're pretty safe leaning under 75% power. The concern is greater on higher power to displacement ratio engines, with 65% power a great rule of thumb in those cases.

[Hank]

6 minutes ago, jakearey said:

And to find peak, the best way is to just lean until a stumble is noticed, correct? 

You can tell peak with your eyes closed. My non-rated wife can tell from the right seat while looking out the window . . . . It stumbles, runs rough, vibrates and loses power rapidly with little bitty movements of the mixture.

Edited April 21, 2020 by Hank

[jakearey]

9 minutes ago, Hank said:

This. The asterisk just makes it easier to remember where it reached peak. The EGT in my C has numbers, which makes it even easier.

Search around here, there are many threads on setting power in C models, with some pretty good explanations. If that doesn't work, type your search into google and add MooneySpace to it.

Many people with IO engines prefer to run Lean of Peak, but it's rather difficult to do with a carb. So I make sure Im below 75%then lean to 50°F ROP. Confirm in your manual, but the EGT marks are often 25° apart. Happy flying!

Oh, a good hint:  the numbers on your Manifold Pressure and tach should add to 47 or less, then you can't hurt anything with the mixture knob. 

I appreciate that. I searched and found several threads that did help but most spoke on power settings and not so much to leaning procedure for the C, specifically.   I’ve seen the Key Number rule vary from 46 to 47 but I suppose both will work and 46 would be more conservative. I appreciate the help! 
 

8 minutes ago, DXB said:

1) Should I forget the asterisk and just lean until I feel a stumble in the engine, note that setting on the gauge and then richen a few notches on the gauge?   

YES!! Or if you have fuel flow, just use that instead of the EGT gauge. You'll find it more reliable.

2)I ultimately want to get an engine monitor and that will be my next mod but I don’t currently have one.   

Definitely do that - it is a terrific diagnostic tool and safety feature...sadly on a carb'd bird it doesn't help leaning much more than the lean to rough/rich to smooth method.

3) And the concern is above 65% power, right?  Can someone help explain the red box and also share their leaning procedure for the C, please? 

Mike Busch's EAA seminars and books explain in some detail.  Bottom line on the 180hp O-360 is that you're pretty safe leaning under 75% power. The concern is greater on higher power to displacement ratio engines, with 65% power a great rule of thumb in those cases.

thank you for the detailed responses! I’ve got Mike’s book Engines but haven’t gotten to this section yet. I’ll refer to that.  Thanks! 

[carusoam]

More about that asterisk....

Rusty asked just the other day...

-a-