tspear
Well-Known Member
Due to time constraints in life, my wife convinced me to buy a plane instead of building one. (Definitely a keeper, agreed to build when retired)
Anyway, one of the planes I am considering purchasing is a turbo charged Velocity, my largest concern is Velocities are known for cooling issues, and this is a turbo charged engine which likely has more cooling issues.
When you look at the Velocity, the typical cooling is a downdraft solution using duck on the top of the engine cowling. Here is a reasonable accurate image of what they look like: http://www.c74.net/xplane/Velocity_XL/0_full.jpg
Now the ducks are in theory NACA shaped and setup. However, the reality is they are so far back the boundary layer has already broken up, and at high angles of attack there is insufficient cooling. Part of the problem is the NACA scoop completes toward of the back of the engine, then the plenum chamber is usually running back to the front of the engine, and the air turns again and runs backward and out for normal downdraft cooling. The S curve adds a lot of inefficiency and likely drag. Armpit scoops have also been tried and work very well, however they add a lot of drag.
The solution most commonly used to pour fuel down the engine and run 200+ degrees rich of peak and climb at a shallow angle with a higher speed.
I view these as band aids; not solutions. In addition I would like to change from standard mags and mechanical injection to the SDS EFI solution, add an inter-cooler and run LOP at high power with a descent rate of climb. Ideally on mogas, but that might be a bridge to far.
The only Idea I have is to move the NACA ducks forward above the existing fuselage, and place an inter-cooler where the existing NACA ducks reside. But I have no idea what this will do to aerodynamics, or if there is a better solution. Any ideas? Is this too complex?
Tim
Anyway, one of the planes I am considering purchasing is a turbo charged Velocity, my largest concern is Velocities are known for cooling issues, and this is a turbo charged engine which likely has more cooling issues.
When you look at the Velocity, the typical cooling is a downdraft solution using duck on the top of the engine cowling. Here is a reasonable accurate image of what they look like: http://www.c74.net/xplane/Velocity_XL/0_full.jpg
Now the ducks are in theory NACA shaped and setup. However, the reality is they are so far back the boundary layer has already broken up, and at high angles of attack there is insufficient cooling. Part of the problem is the NACA scoop completes toward of the back of the engine, then the plenum chamber is usually running back to the front of the engine, and the air turns again and runs backward and out for normal downdraft cooling. The S curve adds a lot of inefficiency and likely drag. Armpit scoops have also been tried and work very well, however they add a lot of drag.
The solution most commonly used to pour fuel down the engine and run 200+ degrees rich of peak and climb at a shallow angle with a higher speed.
I view these as band aids; not solutions. In addition I would like to change from standard mags and mechanical injection to the SDS EFI solution, add an inter-cooler and run LOP at high power with a descent rate of climb. Ideally on mogas, but that might be a bridge to far.
The only Idea I have is to move the NACA ducks forward above the existing fuselage, and place an inter-cooler where the existing NACA ducks reside. But I have no idea what this will do to aerodynamics, or if there is a better solution. Any ideas? Is this too complex?
Tim
