Related Photo Galleries
Both centrifugal and Roots-style blowers make boost dependant on how fast they're spinning. You can change the drive speed simply by changing pulleys. Drive ratios are calculated by dividing crank pulley diameter by blower pulley diameter. Ex: A 7-inch-diameter crank pulley with a 3.5-inch blower pulley equals a 2:1 ratio, or 200 percent overdrive.