Well if you are not a jet pilot then the easiest, safest, and cheapest way to quench your go-faster cravings is Go Karting, the most fun you can have on four small wheels.
Go Karting tracks can be found in both the indoor and outdoor variety. The motorised Karts range in speed from around 25km per hour for Joe off-the-street public to anything up to 80km per hour for the professionals.
Despite actually travelling slower than my grandma on the way to the shops, the sensation is of going much faster due to the fact that you are practically sitting on the track.
It's also a great activity for a group of friends, racing each other for the title of grand poomba of the lilliputian F1 circuit.
I'd recommend an outdoor track if the weather is fine as they are usually larger. Larger tracks are more fun because it takes more time to drive around (less repetition), there are longer straights to get up some speed, and the corners are not all so tight you end up dizzier than a dog on a merry-go-round.
Here is a list of the places you can rev it up in Sydney:
Eastern Creek Karts. The biggest and the best. If you can travel that far and it's not raining then this is the place to go.