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Are my Power Settings OK

Frankster13

Active Member
After Takeoff I retract flaps and turn off boost pump and reduce power to 25 inches MP and 2500rpm for climb. It seems I really only have a few power settings Climb 25"/2500, 24"/2400 rpm (fast cruise) and 23"/2300 (slow cruise). Obviously, as I climb I cant hold that MP but do these values seem reasonable? Is anyone running other settings?
 
I take off and climb at 25/25. I usually cruise at 21/21, 20/22 or 19/23 depending on altitude that gives me around 165 - 170 mph and 195 - 200 above 8,000' at under 8 gph.
 
You didn't say what eng you have but 4 bangers don't do well at low RPM, I suggest 2400 ish as normal minimum rpm, reduce MP as required.
My std cruise is 2400/22 but if just puttering around 2400/18'. Std climb is 2500/25'
 
...TLAR...

RV-7 with Constant Speed Prop and Angle valve IO-360...

I leave everything forward** until I reach cruise altitude, I then reduce RPM as desired, then adjust mixture for LOP -60° (e.g. if peak EGT is ~1450°, continue to lean mixture until EGT is ~1390°).

** I do note EGT on the take-off roll, and adjust mixture during climb to maintain that EGT.**

For high speed cruise I set the RPM at 2500, looking for a fuel flow between 10 and 8GPH depending upon altitude -- ~170KTAS...

For economy cruise I set RPM for 2100, Fuel flow between 8 and 6GPH depending upon altitude -- ~155KTAS...

I *never* adjust the throttle -- it stays wide open until let down/descent. I make note of the MAP but don't try to chase it to a particular value.

There is, of course, a great deal of variability in these numbers due to DA, Pressure, OAT, Weight, bug guts on the wings, size of my midsection :) ...
 
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You didn't say what eng you have but 4 bangers don't do well at low RPM, I suggest 2400 ish as normal minimum rpm, reduce MP as required.
My std cruise is 2400/22 but if just puttering around 2400/18'. Std climb is 2500/25'

Why do 4 bangers not do well at lower RPM?
 
Why do 4 bangers not do well at lower RPM?

Higher cylinder pressures and large degrees of rotation between power strokes would increase the vibe levels, but it likely won't damage anything.

I would be more concerned with prop limitations. Various restrictions Hartzell has published for different props:
1) Continuous operation is prohibited above 22" manifold pressure between 2050 and 2200 RPM

2) Do not operate above 22" manifold pressure below 2350 RPM.

3) Operation above 2600 RPM is limited to takeoff. As soon as practical after takeoff the RPM should be reduced to 2600 RPM or less.

4) Maximum engine RPM must be limited to 2650 RPM.

5) Avoid continuous operations between 2000 and 2250 rpm.

6) Stabilized operation is prohibited above 25" manifold pressure between 2300 and 2550 RPM and below 15" manifold pressure above 2600 RPM.

There's quite a few props that don't like being set at 2100 rpm and left there...
 
Frank,

I suggest that the number of variables precludes a common power setting across airframe, engine and prop combinations. For that matter altitude as well.

Propeller efficiency is not linear, and even the same prop will have different “sweet spots” on the same plane at different altitudes.

What I do (RV-8, IO-360-M1B, standard Hartzell BA prop):
Take off: Throttle, prop and mixture full forward (except for high altitude airports). Prop back to 2600RPM passing 1000’.
Climb: Throttle full forward, 2600RPM, mixture full rich until passing ~4K’ then lean to keep EGTs at about that during the takeover roll, typically ~1250 or so. If a hot day I’ll delay leaning to keep CHTs below 400.
Cruise: 6K’ or so 24” (or full throttle) and 2400-2450 RPM. Leaned to just LOP (10-20 degrees). Yields 170kts at ~8GPH. 11K and above 2500 RPM, full throttle, leaned to 10 degrees LOP - unless CHTS get to low, then leaned to peak (I like to keep CHTs above 350 per Mike Busch’s recommendation - hard to do on a cold day). This will get me ~174kts at ~8gph.

And I’m still exploring settings to squeeze a few more MPG out of Bessie. I could go slower but that is just not in the cards.

But, you need to experiment to find your own “sweet spots”.

Carl
 
How about IO-540s

Good thread. How about those running IO-540s (D4A5) on their RV-10s? I’d be interested in lean and rich of peak power settings and associated fuel burn? Fast cruise and economy cruise LOP and ROP would be great to get info on.

I’ve got 25hrs on a fresh overhaul and have been running 100 degrees ROP so far per my engine shop’s recommendation.
 
Good thread. How about those running IO-540s (D4A5) on their RV-10s? I’d be interested in lean and rich of peak power settings and associated fuel burn? Fast cruise and economy cruise LOP and ROP would be great to get info on.

I’ve got 25hrs on a fresh overhaul and have been running 100 degrees ROP so far per my engine shop’s recommendation.

Look at my earlier post. I did the same process with the RV-10 (stock IO-540 and Hartzell BA prop, James Cowl). The engine was LOP ~90% of the time. Fuel burn at 170kts was 12gph low, 9.5gph high. The plane now has the new six cylinder pMag and the owner reports a ~1gph reduction in fuel burn for the same LOP cruise speeds.

Carl
 
OK, here it is.... some may disagree, but I have been flying for over 45 years, over 30,000 hours, ATP A&P IA CFI DAR. The skinny on engine management...
1. for certification, engines must meet the ability of running 50 hours at full rated power, maximum oil temperature, and maximum cylinder head temperature, and then be inspected, and no anomalies found!
2. I have torn down a lot of engines, many with coked up oil rings, coked up valves, excessive deposits on the piston, and excessive cylinder wear were from operators that thought they were "babying" their engines, running them rich. those that have been run at leak, show very little wear, low deposits, and most likely could keep running for a lot longer with reliability.
3. Most carbureted and fuel injected (non turbo) engines are set for an approximate 13/1 air to fuel ratio. The last bit of throttle enrichens the mixture even more for take off and climb. Throttling back in the climb where there is not as much air flow over the engine than in cruise will cause the EGT and CHT to climb (Bad!!). I leave the throttle full bore, after take off and cleaning up the aircraft, I leave the throttle parked full bore, but bring the prop back to 2500, if fixed prop, don't do a thing! Then, I take a peek at the EGT for any cylinder I like, and use that egt to lean to every 1000 feet or so. (That is the only time that the EGT value means anything to me). At level off, leave climb power in until cruise speed is reached, then reduce power to what you like for cruise, I use 21-22 inches and 2300 below 10K, and full throttle and 2400 above 10K. Then do the big "pull". I know my engines, and know what fuel flow I want to see that will represent "peak" at various power settings. I always lean to peak! Peak egt is a bit flat over the top, my engine runs about .3 gallons per hour from the first to last cylinder to peak. I split the difference. If you look carefully, you will notice that as you lean, the EGT and CHT both climb until about 100 degrees rich of peak, and leaning past that point, the egt continues to climb, but the CHT begins to drop. wonderful! Very efficient, low deposits in the engine, and she purrs like a kitten! So ask yourself, if you are burning less fuel, and the engine is running cooler, what is the problem again?

4. It's your engine, but from experience, there are a lot of old school guys still out there, think running very rich is treating the engine well, when just the opposite is true! (Remember when...probably don't... we sued to pull the prop through before every start to "limber the oil"? Total BS! It was a hangover from the radial engine days, preventing hydraulic lock starts.

5. If you get a chance, read all about running your engine from the articles written by John Deakin, mostly published in AvWeb. There is a lot of pure scientific data there, not old tales, but alas, still can't convince the poorly informed of their poor engine management!

fly Safe!
Regards,

DAR Gary
 
After Takeoff I retract flaps and turn off boost pump and reduce power to 25 inches MP and 2500rpm for climb. It seems I really only have a few power settings Climb 25"/2500, 24"/2400 rpm (fast cruise) and 23"/2300 (slow cruise). Obviously, as I climb I cant hold that MP but do these values seem reasonable? Is anyone running other settings?
Yes very reasonable. Keep in mind you can run OVER SQUARE (slightly higher MAP, 1" for example vs RPM) with some restrictions. Some props may hav limits with RPM/MAP combos.

Consider different RPM's 2250 or 2325 or 2430 for example for least vibration. You don't have even RPM in 100's. If you got your seat of the pants sensitivity on high, you can tell the RPM's that the engine likes, where vibrations are less. A 25 RPM (indicated) change can make a difference.

Keep in mind RPM indicated can be off. Calibration is a good idea.

PS It is recommended to not make any power changes below 500ft to 1000ft after takeoff. Typically loss of power on takeoff happens with change of power.... Up to you.
 
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Yes very reasonable. Keep in mind you can run OVER SQUARE (slightly higher MAP, 1" for example vs RPM) with some restrictions. Some props may hav limits with RPM/MAP combos.

^ This

Recommendation on oversquare...
https://www.youtube.com/watch?v=A1fmNFWNHD4

Also, a fixed pitched cruise prop is operating over-square in a climb until about 6000' MSL. No reason to think a constant speed prop needs to operate differently unless there's other operational reasons (performance, RPM limits, etc.)
 
You didn't say what eng you have but 4 bangers don't do well at low RPM, I suggest 2400 ish as normal minimum rpm, reduce MP as required.
My std cruise is 2400/22 but if just puttering around 2400/18'. Std climb is 2500/25'

Why do 4 bangers not do well at lower RPM?

And would you, Walt, amplify on what you mean by “don’t do well”? Does it do damage? Thanks.
 
After Takeoff I retract flaps and turn off boost pump and reduce power to 25 inches MP and 2500rpm for climb. It seems I really only have a few power settings Climb 25"/2500, 24"/2400 rpm (fast cruise) and 23"/2300 (slow cruise). Obviously, as I climb I cant hold that MP but do these values seem reasonable? Is anyone running other settings?

What altitude do you touch your engine controls and shut the fuel pump? I see too many people who turn off their fuel pump or pull back their engine controls way too early. .I feel if you don't think you could make it back to the field in the event of an engine failure, you shouldn't touch anything yet. .
 
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