Posted for "George Braly" <gwbraly@gami.com>:

 Craig,
 
 A few months ago,  I spent a day at our place with a former Garrett turbine
engineer.   He now works for the FAA.
 
 I posed this question to him.
 
 He pulled out his  old P & W pocket book  - - and we worked our way through
the rather straight forward equations.
 
 The equations don’t lie.
 
 We did the numbers for the IO-720 that one of our friends tried ( rather
unsuccessfully - - it went slower with the belt driven supercharger than it
did without).
 
 The equations showed why.  The blower required a lot of horsepower.  It was
not 70,  but it was close.
 
 Regards,  George