I did that also with my Miatas bag, that puppy launched close to 25 ft in the air.
My best friend who never saw one go off before promptly looked over at his daughters CX-9 which has like six of them in there........ We don't think she would've appreciated us tearing her car apart for a few minutes of explosive fun. 
>Hijack: I have been fortunate enough to not have been involved in a wreck that had bags go off. I could not imagine the deafening sound in that confined of a space.
