I got rid of the ugly prism hanging outside of the fuselage and equipped the airframe with a Rolls Royce Merlin and a new custom sound profile that sounds good at and through all rpms. I also improved the physics. The engine and its sound profile runs at 3,000 rpms for rated horsepower.

If you wish to reuse the sound profile simply add a thruster that makes 3 Newtons (N) of thrust at max and 0.8 Newtons at min thrust, and hook the throttle of the thruster to an rpm Sensor on your main engine.