Unity car tutorial speed boost

I was able to create a working car with the unity car tutorial, however I need help creating speed boosts in my game. Through out my game players will be able to pick up objects that speed up their car for a few seconds. How can I make it so that when a player(car) collides with the objects the car accelerates for a few seconds? What can I call within the car script to do this? Please remember that I'm using the unity tutorial for this car and not my own.