Poll: what power settings do you use on an IO-360?

[AndreiC]

I know this is topic that everyone feels their opinion is better than everyone else's (ha!), but having just started to fly my 1970 M20E (IO-360 fuel injected) which has many more options to set power than my old 1968 Piper Cherokee 180 (O-360, constant speed prop, no engine monitor) I find that I don't have a good idea what power setting to put, what altitude to cruise at, and whether to run LOP, ROP, or at peak.

In my old Cherokee I would generally cruise between 4k and 6k, and set the throttle so the RPM would be around 2400, and then fine tune the mixture and RPM so as to get a fuel flow between 8.8 and 9.3 depending on how fast I wanted to go. That would typically get me between 112 and 117 knots TAS.

Now with the Mooney I have many more choices. To use or not to use "Power Boost" (use unfiltered air) -- gets me another 1.5" of MP. To run WOT all the time? To lower RPM well below 2500 for a quieter ride (say, go down to 2300 or even 2200), or stay at 2500 for going faster? What mixture setting to use? All the experienced pilots at my field, and all mechanics I talked to, are against running LOP, so for now I would prefer to stick to ROP operations. Lycoming's definition of best economy mixture is to run the engine at peak EGT, but this seems stupid as it leads to the hottest CHTs. Should I run LOP 20 degrees? Should I run ROP 20 degrees? I generally don't care about getting the absolute most power possible (so would not run 50-100 degrees ROP) but I would like to get good fuel economy and keep my engine as healthy as possible. 

I have an EDM-700 engine monitor, so I can monitor individual EGT/CHT in real time. I also have the cowl closure mod; I never see CHTs above 320 or 330 degrees, so I think I am doing fine in that respect.

Please let me know your thoughts on the above questions, and what typical power settings you usually use. If you could also add what TAS you tend to get at these settings (specify MPH or knots, please) it would be really helpful too.

Thanks!

[KSMooniac]

You should take the www.advancedpilot.com course and then you'll be able to answer all of your questions and understand why you're getting bad advice from "old pilots and mechanics" that are just repeating the same old wrong information. Hint, 20 ROP is almost the worst mixture setting you can have if you care about your engine. And peak EGT does not yield the hottest CHT!

I run wide open throttle all the time, LOP in cruise, descent, and landing. I know what I'm doing thanks to that course, and encourage everyone else to realy learn what happens when you move the red knob shop they won't blindly follow bad advice. You cannot easily learn all about it in a forum like this.

Sent from my LM-V600 using Tapatalk

[Utah20Gflyer]

I run an O-360 so I won’t comment on rich or lean of peak but I think the WOT and 2400 rpm is a very common power setting for cruise for all vintage Mooneys.  
 

Lately I’ve been experimenting with reducing throttle until I see the faintest sign of manifold pressure reduction and then leaving it there.  I haven’t come to any conclusion however on whether this is a practice that is worthwhile. 
 

Cruise altitude is a function of the distance you are flying and terrain clearance requirements.  I fly in the mountains so 9500 to 12500 is where I cruise at based on not wanting to run into mountains.   If you are a flat lander then the longer the trip the more worthwhile it will be to climb.  For my plane I’ll burn 11 gph at 6500 WOT /2400 for 150 knots or 8 gph at 10500 for 145 knots.    I personally prefer loosing 5 knots and keeping the 3 gallons per hour.   I think a normally aspirated mooney is at its prime in the 10-11k altitude.  
 

Foreflight is nice because it quickly shows you flight time versus fuel burn based on cruise altitude as well as terrain clearance requirements.  That is how I normally choose an altitude.   

[DCarlton]

First, I'm not a mechanic but I'm a retired mechanical engineer so I tend to be technical.  I've flown behind an IO-360 for decades.  My personal opinion; we way overthink this stuff.  I've done a few deep dives into the subject but ended up just keeping it simple.  Once I'm at pattern altitude and the manifold pressure has dropped in the climb, I roll the RPMs back to 2400-2500; usually 2500 at pattern altitude or higher climbing and then 2400 in cruise (sometimes I'll throttle back a tad down low until the MP starts dropping).  Cruise at 8500 to 9500'.  I cruise WOP unless I'm down low or descending.  Never been too concerned about fuel burn, since the 360 is so efficient.  I use the RAM air if I'm on a cross country and feel like a little boost in pressure.  I have an engine monitor and have used the LOP / ROP procedures but most often, I just look at the old EGT gage and roll out a few turns of the mixture until I'm 100ish deg ROP.  For some reason, I've just never warmed up to LOP operations.  Now to. be critical of myself; I should use the engine monitor to find the best ROP setting more often.  It'll be interesting to see what other folks say; the whole LOP ROP thing always results in debate.  BTW, my CHTs are always good; never a challenge to keep in the green.  On a good day, my F with all the J mods is a 153 kt airplane in cruise (from the GPS).  

[Hank]

Andrei, you should be able to run any MP / RPM combo shown in your Owners Manual. I have a C with a carbureted engine, and travel at 7500-10,000msl. When nice and high like this, I run WOT / 2500; I'd be shocked if your IO-360 won't do the same. 

You just need to check your Performance Tables on every flight [I still do after 16 years], and you will soon find yourself using a few repeating power settings most of the time.

An easy way is to learn the Key Number for your engine; this is a tiny part of the training provided by the MAPA PPP [Mooney Aircraft Pilots Assn. Pilot Proficiency Program]. My own Key Number is 46, so your IO-360 is like 48 [read the numbers on your MP dial and Tach, add them up--for me, 20" / 2500 shows on the gages as 20 & 25, which sum to 45; because this is at or below my Key Number, I can put the mixture pretty much anywhere safely. The higher I cruise, the closer I can run to Peak EGT, and fuel economy approaches 8.5 gph block time from engine start to the fuel pump.

Good luck, study hard, fly often and enjoy the process!

[MikeOH]

First off, I absolutely agree that we overthink this!

If I’m going somewhere I climb to 8-10K with WOT and max rpm. I lean to sea level full power EGT (about 1250 for me, yours may be different) during the climb. Ram air on as soon as I’m a few thousand AGL. After level off, WOT, 2550 rpm, 20 LOP. This typically results in 142 kts and 9 gph. (Nets around 65-70% power, IIRC)

1970 M20F IO-360A1A

[Ragsf15e]

I use the “power boost” any time above about 2000’, clean air and not imc.  I also run full throttle all the time unless I’m in the pattern, instrument pattern or sightseeing.  However, I’m always higher than you as I’m out west.  You probably want ~75% or below power, so around 23”/2500 rpm or less for engine longevity according to lycoming.

The mixture is up to you.  Peak isn’t the hottest and it is fine up higher. In fact, it’s probably better than lean of  peak if you get down around 60% power (up around 10,000).  Around 50 rich of peak will be the hottest. You probably won’t want to be there.

you need to learn about 100 rich of peak or ~20 lean of peak and the reasons to use them.  Of course you can use other settings, but these are a starting point.  Up around 8000’ you can use full throttle and experiment with the mixture without hurting anything because youll be at a low power due to the thin air.  I wouldn’t experiment down at your 2-4000’ cruise as you could actually hurt it - which is hard to do in an na 360, but you could potentially get really hot or even detonate down there.

[Oscar Avalle]

Hi my O-360 in my M20C, runs mostly at 2350/23 at 5500 feet with a fuel flow of 8.6 gal/hr. That yields around 138 kts TAS

 

Oscar

[BrianWilkins]

I run 25 square, or at least 25k RPM and whatever full throttle with ram air open gives me, and I lean it to about 11GPH.

[A64Pilot]

I won’t give you any old pilots or IA opinions, but this is Lycoming’s recommendation, but even then some seem to think that Lycoming doesn’t know anything either.