Hate to rain on anyone's parade, but i8 ASD works like all the models, meaning it's sort of a recording that gets played back depending on throttle, etc. There aren't any microphones by the engine or anything. The i8's system actually incorporates an exterior speaker as well, which
is different than other models.
ASD sound files, B38 is included (not my pic):
http://bmwi.bimmerpost.com/forums/showthread.php?t=960956