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  #1  
Old 10-07-2021, 04:44 PM
Charles in SC Charles in SC is offline
 
Join Date: Aug 2006
Posts: 765
Default Power setting question

I know that you loose mp as you climb, but at lower altitudes say 3-5 thousand what power settings do you run? thanks in advance!
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  #2  
Old 10-07-2021, 04:50 PM
rocketman1988 rocketman1988 is offline
 
Join Date: Jun 2010
Location: Sunman, IN
Posts: 2,677
Default How

How fast do you want to go?
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  #3  
Old 10-09-2021, 01:07 AM
FlyinTiger FlyinTiger is offline
 
Join Date: Feb 2009
Location: Gilbert, SC
Posts: 296
Smile Get in the books

Get into your engine owner's manual, there's power curves.

You'll want to be below 75% power when cruising around so you can get the most life out of your engine.

Using your manual you can determine fuel flow at the different altitudes and power settings.

For my angle valve 200 h.p. Lycoming IO-360 the charts are based on running 150* ROP.

Remember, the charts don't show fuel flow for LOP, so you'll have to baseline your own fuel burns for LOP operations.

I put a little chart on my checklist that shows fuel burn, power settings and % power based on the the Lycoming manual. If I pull the red knob significantly more aggressively, to 30* LOP, my fuel flow goes way down at the cost of about 8 knots. My CHTs come down and even out as well.

My wife, who occasionally flies my RV-7, asked for a cheater chart for power settings when she's cruising around the local area and when going cross country.

3000 feet - 20 inches - 2400 RPM - 8.2 gph - 55%
6000 feet - 20 inches - 2400 RPM - 7.6 gph - 57%
6000 feet - WOT - 2400 RPM - 9.8 gph - 71%
8000 feet - WOT - 2450 RPM - 9.0 gph - 65%
8000 feet - 20 inches - 2350 RPM - 8.0 gph - 55%

These are Lycoming book numbers for the IO-360 angle valve engine (200 hp).

Note that lowering the prop RPM to something like 2350 or 2300, depending on your recommended limits for your engine and prop combo, can reduce fuel consumption because it reduces % power produced. It is worth testing to see what changing prop RPM does to your airspeed.

When sight seeing locally or just enjoying a beautiful day at 3000 feet MSL and not going anywhere, setting 20 inches of manifold pressure with 2350 RPM is relatively quiet, keeps the engine very happy and is plenty fast at around 130 knots indicated, plus or minus a few knots. There's no prop RPM limits with my Hartzell two-blade metal propeller and the angle valve IO-360, so occasionally I'll dial it down to 2000 RPM while just flying in the local area.

When going anywhere the most efficient power setting seems to be WOT at 8,500 feet and 30* LOP. If you want to go faster run 150* ROP and gain 10-12 knots and burn 2 gph more fuel.

Get in your plane and go experiment. I love flying with a purpose and a great excuse to go fly is testing things to see what works well for my own flying style.

Does that help?
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Last edited by FlyinTiger : 10-09-2021 at 01:19 AM. Reason: Best range vs speed
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  #4  
Old 10-09-2021, 07:12 AM
swjohnsey swjohnsey is offline
 
Join Date: Nov 2018
Location: Kingsville, TX
Posts: 365
Default

This is my first airplane with CS prop, RV-4 IO360 so I'm not 'xactly an expert. I was dazzled by the power charts. Someone suggested a cheat. Any combination of MP and RPM that adds to 42 will give my around 55% power, ie, 21" x 2100 RPM or 19" x2300. 44 gives me around 65% and 46 yields 75%. I usually putt around a low altitude 21x21 at around 7.5 gpm and 160 mph indicated.
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  #5  
Old 10-09-2021, 08:35 AM
pa38112 pa38112 is offline
 
Join Date: Mar 2008
Location: Clarksboro, NJ
Posts: 1,001
Default

When running LOP, the FF is the power setting. You can ignore MP. On my O-360-A1A I run set my RMP about 2,400 and then pull the mixture out until I get below 75%. I then play with the throttle setting and FF to get a smooth engine at the max throttle position I can.
To calculate the % power at LOP you multiply FF in GPH by 14.9. That is the HP your engine is producing. you then divide that by the rated power of your engine:

8.4 gph X 14.9 hpg = 125hp

125hp/180hp = 69%

This will hold true at any altitude as long as you are lean of peak.
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  #6  
Old 10-09-2021, 08:58 AM
blaplante blaplante is offline
 
Join Date: Jan 2010
Location: Southern California
Posts: 298
Default

I have a JPI engine monitor and it calculates % power for me. And a lot of other nice features.
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  #7  
Old 10-09-2021, 01:34 PM
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Dan 57 Dan 57 is offline
 
Join Date: Sep 2018
Location: LSZF
Posts: 758
Default

thanks for another pop-corn thread
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  #8  
Old 10-09-2021, 02:35 PM
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RV8iator RV8iator is offline
 
Join Date: Nov 2006
Location: Saint Simons Island , GA
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Default

Quote:
Originally Posted by DeeCee 57 View Post
thanks for another pop-corn thread
Ainít that the truth..
WOT,
RPM for phase of flight
FF as desired

Rinse, repeat!
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