Oh boy. I was just thinking that if I made a track five times as long, on a ramp, I could get a 65 MPH pinewood derby car, but it would not be scientific.
Just fun.
Like Mythbusters!
What if you laid a hundred feet of PVC pipe on a good hill, wide enough for the car to roll, sealed as long as you can measure the final speed before it hits a bean bag of bag's worth of cotton balls.
What kind of pressure would you need?