I'm sorry, but you cant make a dog go any faster than what it can do.
Keeping the dog fit yes, to maintain it's speed and performance, but not making it faster!
Some dogs are quicker than others, due to size, the x's, the saluki blooded will stay longer than a bull x where a whippet x will have a quicker take off but lack the pace in time.
So the dog is born with what it is born with!