Belt driven superchargers (blowers) used to be faster to spool up than turbos. Turbo lag was a real thing for a long time, that's why dragsters always used blowers.I'm confused. I could see an electric blower for boost at low rpms giving way to the turbo at higher rpms but a belt driven blower would be rpm-dependent like the turbo. I guest low rpms are still pretty high when driving a fan.