How does acceleration change as a car increases speed?
It depends on meaximum torque that can be produced by the engine and external forces acting on the vehicle. If a car is moving in a place without any external forces like friction or visous force it acceleration is proportional to torque of engine which is constant. But in real world a car experiences lot of external forces and acceleration decreases which is proportional to difference in engine 's torque to external forces. It also depends on maxmimum rpm of engine. If difference is zero then car experience no acceleration.