I dont have a link to it but I saw the original on TV (DAVE) the other night, they were showing the video recording system on the WRC cars, including the sound recordings from the pilot and co pilot and the engine "Effects" channels, one of which sounded distinctly like the knock sensor (if you have ever listened to the knock sensor output). It was clattering away like a mad thing, so bad that I'd be worried about smashing my engine to bits if it sounded like that. Am I being too gentle or are their engines invincible?!