The CX 500 was the first (and perhaps only) motorcycle engine that was designed from the beginning to be turbocharged.
According to the book I read, Honda were actually surprised how civilized and tractable the engine was in normally aspirated form and decided to release the N/A version of the bike as a leader to the "real deal".
I got to ride both a CX500 and a CX500T shortly after they were released, and due to a friend who owned a CX500T having a very long term holiday from his license I got to ride it a lot - including nearly losing my own license in the process. The performance of the turbo version was awesome, but perhaps fortunately for a lot of us the whole turbo experiment kinda of fizzled out after a very short number of years.