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  #1  
Old 11-14-2018, 09:22 AM
HansR HansR is offline
 
Join Date: Jun 2018
Location: Sweden
Posts: 18
Default MAP / RPM chart

I have the combo
O-360 and a Harzell HC-C2YR-1BF CS prop

Now I am looking to find out the most economical combinations of
MAP / RPM at altitudes, ie 2,4,6,8000ft

I try to understand the Lycoming owners manual, and it seems perfectly ok to go significantly under "square".

So I would like a chart in the cockpit with recommendations, ie at 4000ft, what is a good MAP / RPM combination to achieve 55% power.
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  #2  
Old 11-14-2018, 10:18 AM
DanH's Avatar
DanH DanH is offline
 
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Location: 08A
Posts: 8,006
Default

Quote:
Originally Posted by HansR View Post
I have the combo O-360 and a Harzell HC-C2YR-1BF CS prop.

I try to understand the Lycoming owners manual, and it seems perfectly ok to go significantly under "square".
I think Hartzell restricts the combination:

"Do not operate above 22” manifold pressure below 2350 RPM".
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RV-8 SS
Barrett IO-390
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  #3  
Old 11-14-2018, 03:37 PM
Aggie78 Aggie78 is offline
 
Join Date: May 2014
Location: Fort Worth, Texas
Posts: 359
Default

Quote:
Originally Posted by DanH View Post
I think Hartzell restricts the combination:

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

Actually, it also depends on the blades installed, as well as such items as electronic ignitions, etc.

I emailed Les Doud at Hartzell giving him my configuration along with the actual blades installed and the fact that I was running a single Pmag.

Les emailed me back pretty quickly with a reply (which while in my case did not exactly match up with what they had tested, but operating "conservatively" would result in a limitation of "Continuous Operation prohibited above 24" of MP between 2350-2550 RPM."

Here is a quote:

As torsional vibrations increase due to either compression ratio, aggressive electronic ignition systems, Hp increase etc., the operating limitation that is introduced is:

- Continuous operation is prohibited above 24” MP between 2350-2550 RPM

So if you want to operate conservatively, use takeoff and climb power above 2550 RPM and cruise below 2350 RPM, which is how most people operate anyway.

Also, the most important limit to observe is the 2700 RPM redline. Stresses increase dramatically above 2700 RPM. I always scold people when they tell me they’re racing around at up to 2900 RPM!


Doud, Les <ldoud@hartzellprop.com>

Regarding operating over/under square, Mike Busch just had a great webinar on the efficiencies and benefits of operating our engines oversquare.

http://www.eaavideo.org/detail/video...autoStart=true

Worth a listen....
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RV-7/N75WV
YIO-360-M1B
T67-Hicks Airport, Texas
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  #4  
Old 11-14-2018, 04:02 PM
Aggie78 Aggie78 is offline
 
Join Date: May 2014
Location: Fort Worth, Texas
Posts: 359
Default

Quote:
Originally Posted by HansR View Post
I have the combo
O-360 and a Harzell HC-C2YR-1BF CS prop

Now I am looking to find out the most economical combinations of
MAP / RPM at altitudes, ie 2,4,6,8000ft

I try to understand the Lycoming owners manual, and it seems perfectly ok to go significantly under "square".

So I would like a chart in the cockpit with recommendations, ie at 4000ft, what is a good MAP / RPM combination to achieve 55% power.
Hans,

Go dig out your Lycoming Operator's Manual that came with the engine and look in Section 3 for the power chart appropriate to your situation. For example, for my IO-360, I'm using the chart on page 3-36 of this manual.

The power chart gives you both the sea level and altitude performance numbers and also will tell you the safe limits of MP and RPM to operate the engine.

For example, using this chart tells me that at 4000' PA I can operate my engine as low as ~2050 RPM and up to just a little under 25" of MP.

Any combo of MP/RPM can be cross-checked on this chart to make sure you're not outside the operating limits of the engine and obviously, you still have to comply with whatever MP/RPM limits imposed by the prop manufacturer as well.

Hopefully, not taking this topic too far off into the weeds....
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RV-7/N75WV
YIO-360-M1B
T67-Hicks Airport, Texas

Last edited by Aggie78 : 11-14-2018 at 04:06 PM.
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  #5  
Old 11-15-2018, 06:25 AM
Red Mtn flyer Red Mtn flyer is offline
 
Join Date: Jul 2017
Location: Carson City, NV
Posts: 42
Default original point 55%

Hans -

You're looking for 55% numbers: You can generate these from the charts in Lycoming's engine operating manual. Unfortunately, I know of no 'table of values' for % power operating undersquare -- plenty around for oversquare. Roll your own, specific to your engine model charts -- then adjust your table for ram pressure/ loss, etc., with flight test. Get to do it again myself soon, with new LyCon overhaul [IO-320].
If you want a solid introduction to 'best efficiency of operation', look at: INTRODUCING VZ: BEST EFFICIENCY OF CLIMB SPEED
FOR SMALL AIRPLANES, Master's thesis by Norm Howell. If you want to devise operating patterns specific to your airplane, consider buying the BENCHMARK program.
If you "just want numbers to fly" consider buying Benchmark for that geek in the corner at your EAA Chapter, in return for her doing the work...
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  #6  
Old 11-15-2018, 02:13 PM
Canadian_JOY Canadian_JOY is offline
 
Join Date: Aug 2007
Location: Ontario, Canada
Posts: 1,806
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Quote:
Originally Posted by HansR View Post
So I would like a chart in the cockpit with recommendations, ie at 4000ft, what is a good MAP / RPM combination to achieve 55% power.
Hans - I fully appreciate your desire to run at low power settings. You will likely discover if you do some additional reading here that consistent low-power operations can be detrimental to engine health. You might want to consider varying your power setting up to 65% and 75% to keep internal temperatures/pressures up in a healthy range.

Also, it's very important to note that one must use exactly the right power charts from the Lycoming manuals. I had been using the wrong one for some time. Our engine is an O-360-A1F6. I was using the chart for O-360-A engines. It was only last night, as a result of seeing this discussion thread, that I thumbed further through the manual and discovered a completely different chart which was specific to our A1F6 variant (and several others). I noted this (correct) chart doesn't have a line delineating maximum over-square manifold pressure. What an interesting discovery!
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  #7  
Old 11-16-2018, 12:26 PM
Reaver Reaver is offline
 
Join Date: Sep 2017
Location: Claremont, CA
Posts: 50
Default

Quote:
Originally Posted by Red Mtn flyer View Post
Hans -
If you want a solid introduction to 'best efficiency of operation', look at: INTRODUCING VZ: BEST EFFICIENCY OF CLIMB SPEED
FOR SMALL AIRPLANES, Master's thesis by Norm Howell. If you want to devise operating patterns specific to your airplane, consider buying the BENCHMARK program.
If you "just want numbers to fly" consider buying Benchmark for that geek in the corner at your EAA Chapter, in return for her doing the work...
Do you have a link to that software?
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  #8  
Old 11-17-2018, 07:36 AM
Red Mtn flyer Red Mtn flyer is offline
 
Join Date: Jul 2017
Location: Carson City, NV
Posts: 42
Default Benchmark

Meant to include it - sorry:
Go to the Mac App Store, look for 'Seqouia Benchmark'. Long-term development by Alfred Scott, who was Sequoia Aircraft - Falcos, don'tchuno....
But if you generate the base data, it will work for RVs, too. Honest!
"Benchmark allows you to create an interactive flight manual for a piston-engine airplane with a constant speed propeller, single or multi-engined. It is based on a method of performance flight testing and analysis first developed by Boeing during World War II to create accurate flight performance manuals for the B17 and B29 bombers.... it provided the ability to create fuel efficiency charts for a wide range of aircraft weights, payload... at any altitude or temperature..."
You'll need OS X 10.6.6 or later. I don't know of any windows versions.
There's also a VERY good prop perf program out there - windows so not on this computer, don't have the name in front of me -- but that one is not cheap. Predicts calculated values/ needs for prop installations... I use it to convince trike guys NOT to buy that 'sexy' unit, wrong for their engine and flight speeds.
The data crunching available now is SO much better than when I started doing this stuff [mufflemuffle] decades ago.....
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RLSA - A,G,W/S; Falco F-8L
50 yrs of flight and counting
Dues paid 2017, 2018
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  #9  
Old 11-17-2018, 08:49 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 4,557
Default Consider the Kevin Horton Method

I used the Lycoming book values for ball park, then used Kevin Horton's spreadsheets to generate fuel flows & speed for any engine setting at any altitude, temperature, and gross weight. It works phenomenally well as applied to an RV10 and RV7. It takes about 10 data points with two A/F each. Within .2 gph

He wrote, and Kitplanes published, the method. He allows us peons to download the sheets from his website.
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  #10  
Old 11-18-2018, 10:02 PM
Reaver Reaver is offline
 
Join Date: Sep 2017
Location: Claremont, CA
Posts: 50
Default

Quote:
Originally Posted by Red Mtn flyer View Post
Meant to include it - sorry:
Go to the Mac App Store, look for 'Seqouia Benchmark'. Long-term development by Alfred Scott, who was Sequoia Aircraft - Falcos, don'tchuno....
But if you generate the base data, it will work for RVs, too. Honest!
"Benchmark allows you to create an interactive flight manual for a piston-engine airplane with a constant speed propeller, single or multi-engined. It is based on a method of performance flight testing and analysis first developed by Boeing during World War II to create accurate flight performance manuals for the B17 and B29 bombers.... it provided the ability to create fuel efficiency charts for a wide range of aircraft weights, payload... at any altitude or temperature..."
You'll need OS X 10.6.6 or later. I don't know of any windows versions.
There's also a VERY good prop perf program out there - windows so not on this computer, don't have the name in front of me -- but that one is not cheap. Predicts calculated values/ needs for prop installations... I use it to convince trike guys NOT to buy that 'sexy' unit, wrong for their engine and flight speeds.
The data crunching available now is SO much better than when I started doing this stuff [mufflemuffle] decades ago.....
This looks very promising, thank you!

Quote:
Originally Posted by BillL View Post
I used the Lycoming book values for ball park, then used Kevin Horton's spreadsheets to generate fuel flows & speed for any engine setting at any altitude, temperature, and gross weight. It works phenomenally well as applied to an RV10 and RV7. It takes about 10 data points with two A/F each. Within .2 gph

He wrote, and Kitplanes published, the method. He allows us peons to download the sheets from his website.
I found the spreadsheet on his site, but the calculations seem to be broken. Any chance you have a working copy? Otherwise I'll reach out directly to Kevin.
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