Cruise rpm in 912 motor

Re: Cruise rpm in 912 motor

by Tom Kodey » 10 years ago

Tom Kodey

5 48 15

Thanks, Roger. That's really interesting. I remember, way back when I first started flying behind a constant speed prop, I was taught the more efficient prop setting was higher M.P. and lower RPM, both within the manufacturer's "safe" envelop. I guess I never really questioned what "efficient" actually meant in that context.

I can see I'm in for some experiments with pitch settings ...

Re: Cruise rpm in 912 motor

by Rich Provenzano » 10 years ago

Rich Provenzano

20 59 30

Roger,

I read your indept answer to this question.
You certainly stand out in a crowd. I follow your advise, both here and on the CT Forum.
Very few would take the time to so thouroghly answer a question.

Thanks,
Rich

Re: Cruise rpm in 912 motor

by Rob Seaton » 10 years ago

Rob Seaton

3 1.32k 251

I agree Roger is a great asset to the community.
Also this article should have a gold star placed on it! Very interesting and informative! Or maybe a new section just for props?
Rob

Re: Cruise rpm in 912 motor

by Roger Lee » 10 years ago

Roger Lee

131 5.38k 5.44k

Thanks gentlemen.
It makes all that long post finger nub wearing key punching all worthwhile. :lol:

Props are a very important part of an engine setup and seems to be a little misunderstood.
To make it more confusing every prop MFG will tell you they have the best thing since sliced bread. If you don't believe it just ask them. ;)

---

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

Re: Cruise rpm in 912 motor

by Sean Du Toit » 10 years ago

Sean Du Toit

5 9 4

Hi Roger

Thanks for an interesting and informative artical. Could I ask a question from another angle? I have a very short and high field, 500meter at 4700 feet, summer temp around 35 deg C. My plane configuration is an Bushbaby Explorer (similar to a supercub) with a 914T. I have a ground adjustable IVO 3 blade prop. You explanation explains the prop setup from a cruise mode perspective. Does this also apply for setting the prop in a climb mode for short field take off. My prop is set currently at 13 deg. When I tested the WOT the engine rev climbed way over 5600 rpm. With the current adjustment I cruise at around 5000 rpm at 110mph at 30mgh fuel flow around 20l/h, nice and stable. If I course the prop I find the cruise rpm is around 4600 rpm with a low manifold pressure good fuel flow of around 16liter. I read that it is important to ensure a cruise RPM of around 5000 rpm with a pressure of around 30, it is better for the engine. After reading your artical I am concerned that my prop is to flat and "spinning my wheels".