Auxuilury Boost Unit?
 

I don't know if anyone watches or follows Reno Air Races, but there is an aircraft entered in the sport class that I personally like that has a very interesting supercharger- it is an oversize unit that is run off of another engine which is mounted in the place of one of the back seats. he has a 360 cubic engine which performs like a 550 ci engine. has anyone ever heard of an ABU? heard of other aplications?