Hello,
Is there a general rule of thumb as to what density altitude gives you only 75% power or less? Is it fair to say that above that height you will not be able to get in the red box?
Do you have a full meal deal engine monitor? What are your numbers (EGT, CHT, OT)Hello, Is there a general rule of thumb as to what density altitude gives you only 75% power or less? Is it fair to say that above that height you will not be able to get in the red box? Also, has anyone had much luck running a O-360 LOP? If so, do you wait for the last EGT to peak then lean to 50 degrees? I’ve heard some people say that at reduced throttle you cause a more turbulent flow and that helps fuel distribution enabling a carb engine to be run LOP.
FWIW: I have an O360-A4M and over 500hrs of flying with a full Dynon Skyview engine monitor. After trying everything my standard procedure is to set the power where I want, lean until the engine starts to run rough then enrichen until it smooths out. Miraculously the engine monitor shows I am ever so slightly LOP with CHT & Oil temperatures within limits every time.
I guess after 60+ years of experience Lycoming really knows what they are talking about.
I guess I should have said with fixed prop you don't have direct control of RPM for a given MAP as you would with constant speed prop. This is why fixed pitched prop certified planes don't have MAP gauge. RPM is what you set for power. MAP is at a fixed ratio to RPM... for a given altitude."If fixed pitch you can't control MAP (unless you fly higher or lower altitudes). So RPM and density altitude will give you ball park percent power. "
You CAN control manifold pressure up to full throttle with a fixed pitch prop. The throttle controls RPM and MAP at the same time. To get 75%, just move the throttle till the rpm (rounded to the nearest 100) and the manifold pressure added together = 48. As this number drops, so does the % of power.
but always wondered if it held true as the RPM drops precipitously LOP. After you add in more throttle to bring the sum of MP and RPM back to 48, are you really at 75% power again?
I guess I should have said with fixed prop you don't have direct control of RPM for a given MAP as you would with constant speed prop. This is why fixed pitched prop certified planes don't have MAP gauge. RPM is what you set for power. MAP is at a fixed ratio to RPM... for a given altitude.
Yes, but MAP will tell you if you are getting the power loaded to the prop. An under pitched prop will give you 2700 rpm without using all of the available power.