4 stroke engine exhaust fed to high air flow

[Chevreuil]

Hello,

So say that I have a small four stroke engine that is designed to be kept static at ground level. I then take this engine and mount it to a small air plane, feeding the engine with either still air from inside the cabin (cargo) or the outside wind. The exhaust is fed out to the wind rushing by be plane in flight.

What happens to the performance of my 4 stroke engine? What can I do to minimize performance loss as much as possible? Should I put a venturi valve on it? I am assuming that it is not desirable to change fuel consumption or the engines power output.

If this is a weird question then I'd appreciate some tips on what topics to google. I don't really know much about engines.

 

[Mech_Engineer]

An aircraft's engine performance decreases with altitude due to decreasing atmospheric density; the higher you go in the atmosphere the lower the density of the air. Because of this, there is less oxygen available for combustion.

Atmospheric pressure variation as a function of altitude:
https://en.wikipedia.org/wiki/Atmospheric_pressure

A 4-stroke engine will be especially limited unless a form of forced induction is utilized such as a supercharger. See here: https://en.wikipedia.org/wiki/Supercharger#Aircraft

Superchargers are a natural addition to aircraft piston engines that are intended for operation at high altitudes. As an aircraft climbs to higher altitude, air pressure and air density decreases. The output of a piston engine drops because of the reduction in the mass of air that can be drawn into the engine. For example, the air density at 30,000 ft (9,100 m) is 1⁄3 of that at sea level, thus only 1⁄3 of the amount of air can be drawn into the cylinder, with enough oxygen to provide efficient combustion for only a third as much fuel. So, at 30,000 ft (9,100 m), only 1⁄3 of the fuel burnt at sea level can be burnt.[14]