Hi Compound
It depends on a number of factors; the track that you are racing on, the power that is available, the type of hand controller that you use, what modifications the rules permit, and most importantly, the size of your wallet!
The fastest slot cars in the world -- excluding drag cars -- are Group 7 "wing" cars, such as the one below. They get around a 155' long track in around 1.5 seconds.....
Picture courtesy of
Old Weird Herald.
However, you will most probably find that the fastest way around any slot car track, regardless of the class of car, is a combination of good handling, coupled with good brakes and acceleration -- not necessarily out and out straight-line speed.
Short of scratch-building your own chassis and buying a $300 cobalt magnet motor to go in it, your best bet is probably a TSRF32 car, available in the UK from
AB Slot Sport.
Kind regards
Russell