Impressed by the third party tuned Ariel Atom turbo'd up to 425 bhp (from 2 litre Honda). Not the fastest though, Ariel now have their own 4RR having taken it up to an insane 525 bhp - that relates to 780 bhp per tonne
Having driven the supercharged Atom on a track day even at only 300 bhp ? it was a skittish little blighter and let go without warning on a couple of corners much to my embarrassment
