If speed of a car becomes 2 times, its kinetic energy becomes

Kinetic energy (K.E): The energy possessed by a body and by the virtue of its motion is known as kinetic energy.

We know that, kinetic energy,

$E=\frac{1}{2}m{v}^2$

For same mass, $E\alpha v^2$

Therefore, if the speed will increase by 2 times, then the kinetic energy will increase by 4 times.