More powerful means using more power. Which also means draining batteries faster. Power is "Watts". If you have a motor that runs on 5 volts and draws 100mA then you'll get 0.5 Watts of power. If you change the motor to one that draws more amperage, say 200mA then you'll be using 1 watt of power. If this is battery powered then you're draining your battery twice as fast. And the speed of the RC Car WILL be higher but it will run out of energy faster.this engine and miles long, more powerful
Engine is often used by those where English is not their first language. !And usually the term applied to describe an electric motor is "motor", while an engine is an internal combustion device.