Power Setting Chart

[Guest]

Has anyone made any good power setting charts for the IO360 in my M20J?  I don't care for the presentation in the POH.  I also prefer to run at peak EGT or just slightly LOP. I also like to run oversquare around 2200-2300 rpm. I searched for a while and couldn't find anything.  I don't mind doing the work to produce these, but I just don't like burning the brainpower on a problem that has already been solved.

[802flyer]

Has anyone made any good power setting charts for the IO360 in my M20J?  I don't care for the presentation in the POH.  I also prefer to run at peak EGT or just slightly LOP. I also like to run oversquare around 2200-2300 rpm. I searched for a while and couldn't find anything.  I don't mind doing the work to produce these, but I just don't like burning the brainpower on a problem that has already been solved.

This could easily bloom into a thread many pages long. But the short version is that if you are at peak or on the lean side, you can multiply the fuel flow in your IO-360 by 15 and have a pretty good approximation for horsepower, then divide by your max of 200hp for your percent power.

As an example, 8.7gph (LOP) x 15 = 130hp being produced. Divide by 200hp yields 65% power.

So set the prop where you want it, and then do some simple math to set your fuel flow. As long as you’re confident that you’re LOP (eg having performed a Big Mixture Pull and not re-enriched past peak), then you know what your power setting is. At 2200-2300 and reasonable altitudes, you’ll likely be under 65% and therefore have a lot of wiggle room.

I’ve never bothered to make a chart because I know that if I set 65% power, I’ll usually be between 148 and 152 kn depending on exact conditions. if I’m flying at 6000 I’ll set the RPM at 2400, if I’m in the low teens I’ll set it at 2550, and elsewhere will be somewhere in between. Within those boundaries, that gives me enough room on the lean side of peak to set power with fuel flow (all WOT).


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[Guest]

Thanks for the good info.  I like easy rules of thumb like that.  Kind of a side question, I noticed that most Mooney pilots like 2400+ rpm as the power setting.  Is there a good reason for this?  I have noticed that my own engine is much smoother and quieter around 2200-2300 rpm range.  I am no expert, but it seems to me that in general lower rpm should also be better for long term engine health.  I see high rpms as a great way to get more power if you need it, but in cruise, doesn't seem all that necessary to me.  I am sure that I am missing something...

[802flyer]

Thanks for the good info.  I like easy rules of thumb like that.  Kind of a side question, I noticed that most Mooney pilots like 2400+ rpm as the power setting.  Is there a good reason for this?  I have noticed that my own engine is much smoother and quieter around 2200-2300 rpm range.  I am no expert, but it seems to me that in general lower rpm should also be better for long term engine health.  I see high rpms as a great way to get more power if you need it, but in cruise, doesn't seem all that necessary to me.  I am sure that I am missing something...

Many of us have prop/engine pairings with limitations somewhere between 2100-2350 RPM, where we’re not supposed to run in that zone continuously. So 2400 is an effective lower limit for some.

Down around 2100, it would be harder to make 65+ percent power lean of peak at medium/higher altitudes


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[EricJ]

Many keep it very simple:   Full throttle and full forward prop pitch for takeoff and climbout.    For cruise, pull the prop back to 2500 rpm.   Lean as desired.  Throttle stays full forward.

Reduce power as necessary for descent and pattern entry, prop goes full forward once power is pulled back enough in the pattern to not affect rpm.

 

[Igor_U]

^^^^^^^^ 

This pretty ,much describes my operation. Simple!. It helps that anywhere you go from here has to be 8k ft. or higher except to Jeffco for coffee and pie.

 

 

[Guest]

All good info.  Just curious, my POH recommends 26 squared for climb power.  Is there any implication as far as engine wear leaving it max and full throttle?  I am sure that it climbs better with everything forward though. I am at near sea level, so climbing out with full throttle on a day like today, I am getting about 30" MP and 2700 RPM.  (I took off today with a Cherokee on a parallel runway and just ate his lunch. The tower wanted me to follow him, but I was at pattern altitude long before him, and had to throttle back to 15" to follow.)  The motor seems a little rough at wide open and 2700 RPM.  It smooths out a little bit when I pull it back to 25 squared which is kind of the old school generic climb setting that I learned years ago when learning to fly.  It gets much smoother once I pull the power further back and set 2300 RPM.   However, that all being said I like Eric J's simple plan. If it won't hurt anything, that is probably the way to go.

 

[Pinecone]

Current wisdom is full throttle, max RPM for climb.  Lean to target EGT based on take off roll,

[EricJ]

1 hour ago, Kerrville said:

All good info.  Just curious, my POH recommends 26 squared for climb power.  Is there any implication as far as engine wear leaving it max and full throttle?  I am sure that it climbs better with everything forward though. I am at near sea level, so climbing out with full throttle on a day like today, I am getting about 30" MP and 2700 RPM.  (I took off today with a Cherokee on a parallel runway and just ate his lunch. The tower wanted me to follow him, but I was at pattern altitude long before him, and had to throttle back to 15" to follow.)  The motor seems a little rough at wide open and 2700 RPM.  It smooths out a little bit when I pull it back to 25 squared which is kind of the old school generic climb setting that I learned years ago when learning to fly.  It gets much smoother once I pull the power further back and set 2300 RPM.   However, that all being said I like Eric J's simple plan. If it won't hurt anything, that is probably the way to go.

It doesn't hurt anything to run it full throttle.   If it gets rough while climbing, lean as you climb to maintain initial takeoff EGT (assuming you have an engine monitor).   An engine monitor is often useful for sorting out roughness.   If lowering the rpm smooths it out, it may just be vibration which can be improved with prop balancing if that's the issue.   I'd just give it time and see what you get used to or not or what seems to really be a problem or not.

[Guest]

Pinecone,

 

I'm curious, what do you mean to lean based on takeoff roll?   My personal technique is just to pull the mixture until I get a little roughness and richen it just enough to smooth it out.  That gets me quickly to the ballpark.  Then I reference the EGT gauge to find peak and then run anywhere between a little LOP and a little ROP depending on CHTs and oil temp.  I like getting to know other techniques. Thanks.

[skydvrboy]

1 hour ago, Kerrville said:

I'm curious, what do you mean to lean based on takeoff roll?

I'm pretty sure he's referring to high density altitude operations.  If you know what your EGT's are during a sea level full power, full rich takeoff, then you can lean to that target EGT during your takeoff roll and ensure you are getting maximum power without hurting your engine.  As you climb, continue leaning to that target EGT.

 

1 hour ago, Kerrville said:

Then I reference the EGT gauge to find peak and then run anywhere between a little LOP and a little ROP depending on CHTs and oil temp.

It sounds like you are using a single probe EGT.  If so, I would caution you about running a little LOP and certainly a little ROP.  That only tells you when a single cylinder peaks and others may be running richer and and in a danger zone.  Unless you have EGT's and CHT's for every cylinder, you just don't know.  That said, I ran LOP with a single probe EGT for a few  years until I got an engine monitor.  However, I was very cautious to run very LOP to be on the safe side, as in 50 degrees lean of peak.  You can't hurt your engine by running too LOP, but you can certainly hurt it by not running LOP enough!

[midlifeflyer]

4 hours ago, Kerrville said:

Pinecone,

 

I'm curious, what do you mean to lean based on takeoff roll?   My personal technique is just to pull the mixture until I get a little roughness and richen it just enough to smooth it out.  That gets me quickly to the ballpark.  Then I reference the EGT gauge to find peak and then run anywhere between a little LOP and a little ROP depending on CHTs and oil temp.  I like getting to know other techniques. Thanks.

What you eventually discover with leaning is that the EGT for a properly leaned engine for a certain percent power is fairly constant regardless of altitude. So the idea is, if your sea level standard day, full rich, full power Vy climb shows an EGT of 1350, leaning to that value during the climb  will maintain best power.  It's gets you into a small ballpark with a multi-probe engine monitor.  A much bigger ballpark without one. And yes, ultimately you want to be watching those cylinder head temps.

In cruise, it's the technique to bypass the "Red Box" with the "big pull" when operating LOP, but even ROP, it gives you an EGT target to shoot for.

[Wingover]

On 4/5/2024 at 3:38 PM, Kerrville said:

Has anyone made any good power setting charts for the IO360 in my M20J?  I don't care for the presentation in the POH.  I also prefer to run at peak EGT or just slightly LOP. I also like to run oversquare around 2200-2300 rpm. I searched for a while and couldn't find anything.  I don't mind doing the work to produce these, but I just don't like burning the brainpower on a problem that has already been solved.

Maybe this will help. Key numbers for easy power settings plus the whole article 

Mooney instruction .pdf

[Pinecone]

6 hours ago, Kerrville said:

Pinecone,

 

I'm curious, what do you mean to lean based on takeoff roll?   My personal technique is just to pull the mixture until I get a little roughness and richen it just enough to smooth it out.  That gets me quickly to the ballpark.  Then I reference the EGT gauge to find peak and then run anywhere between a little LOP and a little ROP depending on CHTs and oil temp.  I like getting to know other techniques. Thanks.

That is a VERY dangerous way to run.

If you lean to roughness, you might be slightly LOP, then a slight bit richer puts you right in the Red Box/Red Fin zone and at a high power setting.

As stated, best to lean to sea level take off power EGT, and maybe a slight bit richer.

[ArtVandelay]

For high altitudes I use rule altitude (1000s) + fuel flow (gph) = 19.

So in Denver, 19-5=target fuel flow of 14gph.

[Guest]

Art, that's a great rule of thumb. I like it.

Pinecone, I get what you are saying now.  I have an old insight multi-robe egt.  So using that, you are just matching the bar graph to what you see at sea level.  Logical.  

Wingover, thanks for the table.  That is exactly what I need.  I like rules of thumb, but my friend who flew my plane likes the charts and that one is simple. 

[Guest]

Wingover, that article is great information to go with the chart. Thank you so much.