Grid is a racing game for the PS3 Xbox360 and PC, the throttle is velocity sensitive and can be "feathered" and "stabbed" producing different sounds. In the video there are examples of both these.
When the throttle is applied smoothly the sound is smooth and progressive. when the throttle is applied in stabs the sound seems more throaty and harsh. weather this is just an imagined effect or this is true is unknown.
The resulting engine sounds in grid make the game experience very realistic