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Sea level WOT/2700 RPM


kaba
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Opionions....M20J IO 360 A3B6.....if the engine is designed to run max power/ 2700rpm continuous...

Other than saving fuel by slowing....is there any harm to engine by running fast.......

Should it theoretically reach TBO??

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14 minutes ago, kaba said:

Opionions....M20J IO 360 A3B6.....if the engine is designed to run max power/ 2700rpm continuous...

Other than saving fuel by slowing....is there any harm to engine by running fast.......

Should it theoretically reach TBO??

Not as long as it's got enough fuel flow.

Typically the prop is not most efficient at 2700 rpm. For example, the prop on my plane is most efficient, according to the book, at 2500 rpm. When I had an N/A Mooney, I always ran it WOT. But at 2500 for best pull from the prop and then adjust the mixture accordingly to give best power or best range depending on the requirement of the flight.

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I’m not really sure a 200 HP angle valve Lycoming would handle 2700 RPM for a long time.  The lower powered parallel valve version is more likely to last.  There is a Texas family who have raced their Twin Comanche extensively at full rated RPM with no harm.

Clarence

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I wouldn't run my J that way for long. This time of year with air temps as high as they are mine bumps 380 in initial takeoff seal level climb but not sure what it would do in level flght that low. I'd probably have to keep cowl flaps open at least partially or if I was racing I'd have to adjust to be partially open even when closed. 

I think heat would be the limiting factor. 

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I would climb full power at 2700 RPM every time all the way to altitude in my m20f and would run 2700RPM above 15,000ft. End result. 200 hours past TBO and the engine started making metal from lifter spalling — likely related more to the 20+ years since overhaul. After one 2700 RPM trip, I started getting prop grease down the blades of the Hartzell, but I think that was related to the IA over greasing it at annual. 

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TBO is not a scientific number, it’s basically a guess.
The certification process consists of 3 test runs:
Full power for 50 hours with adequate cooling to keep temperatures in green.
Full power for 50 hours with temperatures at redline.
65-75% power for 50 hours at redline.
Oil changes after each run, engine inspection is done. That’s it, there is no tests to see if engine will make TBO. I believe the warranty on a new engine is something like 2 years/500 hours.
Compare that to automotive warranties.

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9 hours ago, Bartman said:

I wouldn't run my J that way for long. This time of year with air temps as high as they are mine bumps 380 in initial takeoff seal level climb but not sure what it would do in level flght that low. I'd probably have to keep cowl flaps open at least partially or if I was racing I'd have to adjust to be partially open even when closed. 

I think heat would be the limiting factor. 

I’ve spent quite a bit of time at sea level or 1000’ DA and full throttle with 2700 RPM. The CHTs are 330 with a full rich mixture.  That’s cowl flaps closed.  You can even lean a bit down to about 16 GPH. It’s cool and fast. Just not very efficient. 

Edited by jetdriven
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The most harm you can do to your engine comes from neglecting to fly it once a week and/or neglecting to change the oil frequently enough. 

Think about how much abuse flight school aircraft endure and it’s not uncommon to see those engines with 4000+ hours on them with original cylinders. 

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The most harm you can do to your engine comes from neglecting to fly it once a week and/or neglecting to change the oil frequently enough. 
Think about how much abuse flight school aircraft endure and it’s not uncommon to see those engines with 4000+ hours on them with original cylinders. 

I thought flight schools being a commercial operation need to O/H on TBO?
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My cruise setting for anything under 2500' MSL is 2350 RPM, 18" MAP, and leaned as far as possible without running rough.  That nets me about 110 mph and some really low fuel flows.  The only reason I'm flying that low is because there's something I want to look at and if there's something I want to look at, I don't want to blow past it.  

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The mechanical engineers who do things with engines tell me the best way to make you engine last is to run it around 65-75% power.  If you can do it spinning it that fast have at it.  My guess is you'll have an easier time keeping the power down if you run lower RPMs.

The reason we fly Mooneys is their incredible efficiency.  Not terribly efficient running balls out.  Lots of fuel burn for not that much extra speed.

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31 minutes ago, steingar said:

The mechanical engineers who do things with engines tell me the best way to make you engine last is to run it around 65-75% power.  If you can do it spinning it that fast have at it.  My guess is you'll have an easier time keeping the power down if you run lower RPMs.

The reason we fly Mooneys is their incredible efficiency.  Not terribly efficient running balls out.  Lots of fuel burn for not that much extra speed.

There is no problem keeping power in the 65-75% range (if that's what is desired).  Just pull the throttle back.  I run 2600 RPM all the time in cruise.  For 75% I start at 24" MP and for 65% I start at 21" MP.  Lean to just barely LOP, then adjust the throttle to 10 GPH or 8.7 GPH respectively as desired.  I usually don't car that much and am happy with something in the 9.5 GPH +/- range.  I don't reduce the RPM until I need to slow down.  And then I don't pull the RPM back to 2200 unless the MP is below 20" (usually 15").

Both the higher RPM and lower MP push the peak pressure further past TDC which reduces peak pressure and reduces CHT (at least it does for me).  And my engine runs smoother at the higher RPM.  I also think the lower peak pressure helps to reduce blow by which in turns helps to keep my oil clean with less of it blown out the breather tube.

Just my personal opinion of course.

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Some summary...

1) Fuel flow, Oil temps, cylinder temps, vibration, and sound...

All Things to keep an eye on...

2) If your POH lists the power choice as usable then expect that you can safely use it... although, old POHs are not very good for guidance...

3) Read around here and you will see people have the throttle fully in from T/O to Landing.. often climbing out at about 300°F ROP. But....

In a normally aspirated engine at 8k’ it is only generating 65%hp or so... as the MP drops with alt...

4) Pushing it harder by leaving the rpm at 2700 uses a significant amount of fuel with not much benefit... more of an economics question.

5) maintaining CHTs on hot days often requires a lot of extra FF...

6) Having a decent engine monitor is highly recommended...

7) having the prop dynamically balanced makes a lot of sense.

8) Redlines and yellow arcs are worth observing...

9) Experimental Aircraft love to exceed red line for additional power...

10) a well built, and well maintained, and often run engine... goes the distance...

This is a summary of what I read, it is not anything I know about personally... PP thoughts only... :)

Best regards,

-a-

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As I am new to Mooneys and only 25 hours flying my J. I have been operating it as I was when I flew a Piper Arrow, Twin Comanche, Cessna RG, etc

First x country last week from DE to FL and back. Around 6k I have no more throttle left. Run 2650RPM up to altitude (9k-12K) then pull it back to 2400RPM. Lean to -50 LOP. Im guessing im producing around 55%-65% power. No way of telling besides the book. Roughly 150KTAS

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