I am just starting to research the possibility of adding a supercharger (belt drive) as another mod to my Sierra (4.3L engine). In the scant perusing of threads on this subject I am unable to come to a conclusion as to wether or not this will be of benefit to increasing my mpg, assuming I stay with my conservative driving techniques. I am interested in hearing experiences from members about this subject. Meanwhile, I continue my research. Thanks in advance for the assisitance.
Superchargers are always sapping power, so there's no way you'll see a mileage improvement with one. Small turbochargers (because they run off waste exhaust) combined with smaller engines can show mileage improvements, but you're not likely to see any from adding one to your 4.3 L V-6. You'd have to drop to a 2.8 or 2.4 with turbo - something like that.
I've looked into this as well. The best claim I've ever heard, including from a manufacturer, is that you don't lose mileage (which I have a hard time even believing that, since it takes some power even to spin a naked assembly).
The only real way to truly gain MPG with a supercharger is in conjunction with a smaller motor. For instance, swap your NA 4.3 for a supercharged 2.8.
BTW my own prediction is that in the next 10 - 20 years, if we are still using gasoline engines, it will be with very small (0.7 liter) motors with huge turbochargers (30 - 40 #s of boost).
I totally agree with everything that has been posted in this thread.
As allready said: if you compare e.g. an atmospheric 5 liter engine and you downsize it to a 2.8 with turbo. Yes, than you can increase mpg for the same BHP. But with a charger: no way you can increase mpg. A charger's eating fuel on its own !