Cruise RPM
Posted: Thu Apr 20, 2017 4:19 pm
by bakerde36
I have the Hummel 2400 and I am getting 3100 on Takeoff and about 3200 in cruise. My question is should I pull back my RPM in Cruise to 80% and would I use 3200 I see in straight and level and use 2600 or Use stated RPM for engine 3600 @ 80% and use 2900? Or does it even matter about reducing RPMs I want my engine to last and be reliable. Thanks Densil
Re: Cruise RPM
Posted: Thu Apr 20, 2017 5:09 pm
by radfordc
Your numbers are a little strange. My old Aerovee would turn up 3100 on takeoff and max out at 3500 in level flight. Cruise rpm was 3200…which was about 80% power.
What prop do you have?
Re: Cruise RPM
Posted: Thu Apr 20, 2017 5:12 pm
by radfordc
Here is a power chart for the Aerovee: http://www.sonex604.com/percent_power.html
Re: Cruise RPM
Posted: Thu Apr 20, 2017 7:31 pm
by rizzz
What propeller do you have?
My engine is largely a Hummel as well (the accessory package being the biggest difference).
I have a prince P-Tip 54x48
I see around 3000 on takeoff, climb out at 60KT and get up around 1000fpm with just myself in the plane.
I can max out at around 3450 full power straight and level. That pushes me to about 150KT (see: https://www.youtube.com/watch?v=tqVj2IJEbHI&t=13s)
I tend to pull back to 3100 for cruise which gives me about 125KT at lower altitudes.
You shouldn’t compare the Hummel to the AeroVee numbers too much.
The Hummel has a little bit more power but more importantly a significantly longer stroke (86mm) which makes the higher torque is at lightly lower RPMs (that’s my understanding anyway).
Re: Cruise RPM
Posted: Fri Apr 21, 2017 9:02 am
by bakerde36
I have the Prince 54x50 P-Tip which is what Lonnie Recommend.
I normally climb out around 90 to make sure I keep temps cool.
at WOT I am seeing 3200 and showing about 120mph now I do not have my landing gear fearing’s on yet or wheel pants maybe this weekend I will get them done.
Re: Cruise RPM
Posted: Fri Apr 21, 2017 9:04 am
by bakerde36
I am using MPH
Re: Cruise RPM
Posted: Fri Apr 21, 2017 6:05 pm
by rizzz
Honestly, I think your prop might be overpitched for the 2.4L Hummel. I always thought my 54x48 was a bit ambitious and I have considered switching back to a 54x46.