I bought my son a thing that plugged into the cig lighter socket and made a brilliant v8 noise through his radio.
He'd just sold a TVR which made a wonderful noise and we plugged this into his fiat panda 4*4 thing he uses on the fields down there taking straw etc. to their horses, and it was a complete hoot. Revved matching the engine revs somehow though only plugged into socket, no other connection.
It really was smile making although he threw it away after a week or two.
Another £30 down the drain....
Nick