[SpEEdyBL]

Obviously your speed threshold has nothing to do with the motor or batteries. Aerodynamics is the ONLY thing that should matter. Next time you are on a highway, stick your hand outside the window and see how much force the wind can push. That's likely the same amount that is pushing against your mini revo. For starters you need the chassis to be as close to the ground as possible by maybe putting some foam underneath to fill in the space if you can't get it low enough. You also need a body that completely covers the wheels.