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-   -   Constant Speed Prop Power Settings (https://vansairforce.net/community/showthread.php?t=192844)

VF84Sluggo 03-01-2021 06:43 AM

Constant Speed Prop Power Settings
 
Folks,

For those running an IO-360, what power settings do you use? What are your nominal TAS cruise speeds and fuel burn?

I realize this will vary with cruise altitude, OAT, etc. Just looking for "ballpark" settings for cross-country planning purposes.

Thanks in adevance.

calpilot 03-01-2021 08:01 AM

There is a graph in the operators manual, takes into consideration density altitude.
A quick and dirty rule of thumb is RPM in hundreds and manifold pressure:

43 - 55% 45=65% 48 = 75%
Most run 65%; your engine at 22" 2300 RPM leaned to peak should burn 8.2 to 8.5 gph depending on the injector balance. or full throttle and 2300 at 9000' density altitude. depending on propeller, should see 175-183 mph.

RVDan 03-01-2021 08:33 AM

I have an O360 converted to FI with the Airflow Performance system. Hartzell CS prop (wide blade). Electronic ignition. For economy cruise I use 2280RPM 23.5Ē and LOP -30 or so. Depending on altitude which for me is mostly below 6,000 MSL, yields 6.8 gph or so. According to Dynon it is somewhere around 55% power and 150 kts true.
Above 5,000 if I am in a hurry, I cruise at 2300 RPM, WOT, which yields about 70% and 7.5gph and a bit more than 160 kts true. I can usually go LOP -40 in this condition. The go fast mode would be 2450 RPM, WOT above 5,000 ft. I rarely go there for an extra 5 to 8 kts.
As Lindberg proved during WW II, if you can go over square or better yet, WOT you reduce the engine pumping losses and generally get better economy.

Stay out of the Red box. If you donít know what that is search the forum and you should find a lot.

swjohnsey 03-01-2021 08:35 AM

I use a similar formula. I cruise 21x21 until I can't get 21" Hg then increase RPM to get 42. I indicate around 165 mph which trues out around 200 mph at 10,000. Burn is around 8 gph.

VF84Sluggo 03-01-2021 08:38 AM

Quote:

Originally Posted by RVDan (Post 1506910)
Stay out of the Red box. If you donít know what that is search the forum and you should find a lot.

I do not know what that is.

RVDan 03-01-2021 08:49 AM

I donít know how to post a link to a thread, but search in the forum for ďlean red boxĒ, and you will find several threads on it.

scrollF4 03-01-2021 08:51 AM

Mike Buschís red box video
 
Itís long but definitely worth the time.

https://youtu.be/X-tKyiUZ3ts

RV10inOz 03-01-2021 03:49 PM

It is not Mike Busch's red box actually, but anyway.

The simple answer is Wide Open throttle all the time unless you need to slow down.

Prop.....anywhere in the 2300-2500 range, that is smooth and happy, most find the 2350-2450 area works well.

Red Knob..... Full rich for take off, WOT/2700 in the climb, lean occasionally to keep your EGT's in the 1280-1320 range. Once at cruise altitude do a big mixture pull, then fly LOP to destination.

IO360 will burn about 7.9USGPH in the 8-9,000 feet range, more down low, less up higher. I can give you a rough number but you just need to refine the BMP technique.

John Deakins articles make this easy to read and understand. Read articles 63-66 here https://www.avweb.com/features/avweb...s-perch-index/

Read the rest too.

https://www.advancedpilot.com/onlinecourse.html

VF84Sluggo 03-01-2021 05:22 PM

Great info.

Staying at WOT is something new to me. I was taught the ol' "keep it square" rule from my early days. I'm going to have to get my mind around all this, that's for sure.

Toobuilder 03-01-2021 05:27 PM

Quote:

Originally Posted by VF84Sluggo (Post 1507065)
Great info.

Staying at WOT is something new to me. I was taught the ol' "keep it square" rule from my early days. I'm going to have to get my mind around all this, that's for sure.

That is an OWT that started back in the radial days. If Im going somewhere cross country the throttle is advanced to the stop on takeoff and not touched again until on the descent. Power is managed with RPM and mixture, just as David suggests.


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