The kit comes with a "stock" motor.  While stock doesn't necessarily mean cheap, the one that comes with the kit is cheap.  Although it will serve you well for getting started and you should use it until you learn how to control your car, you will undoubtedly want more performance.  And there are lots of performance options in this area.  The motor used on 1/10th scale electric cars is called a 540 size motor.  Many different types of motors are available from many different manufacturers.  The stock motor that comes in the kit has bushings instead of bearings, non-adjustable timing and non-replaceable brushes.  Motors are rated primarily by the number of turns.  Stock motors have 27 turns (27T) of 22 AWG copper wire on the armature.  "Hotter" motors have less turns, such as 10 (10T), adjustable timing, ball bearings, stronger magnets, capacitors to minimize arcing, and replaceable/better brushes.  As the number of turns decreases, so does the resistance thus drawing higher current.  While the higher current produces more power, battery life per run is reduced.  The same goes for better conductive brushes and stronger magnets.  The idea is to increase current draw and higher power at the cost of run time.  Although stronger magnets and better brushes can increase efficiency.  Few motors have efficiency ratings.  Some motors have double and triple windings.  These are used primarily to spread power to the mid and high RPM ranges.  I like the Trinity P2KPRO2 "stock" motor which is a stock replacement 27T fixed timing (24 degrees) motor.  It has replaceable brushes and a copper end bell for better heat dissipation.  I also use ball bearings to replace the bronze bushings.  This motor has plenty of power for me and provides a decent efficiency and long run time.  However, for "stock" racing rules, you would have to put the bushings back in.