Decreasing the accessory pulley diameter results in what change to parasitic drag?

Decreasing the accessory pulley diameter results in what change to parasitic drag?

• A. Decrease parasitic drag
• B. Increase parasitic drag
• C. No change in parasitic drag
• D. Parasitic drag becomes negative

Answer: (B)

Reducing the accessory pulley diameter makes the belt drive the accessory spin faster for the same engine speed. The engine must supply power to drive that accessory, and power equals torque times angular speed. If the accessory torque stays the same but its speed goes up, the power the engine must provide to run the accessory increases. That extra power draw shows up as parasitic drag, so parasitic drag increases when you decrease the pulley diameter.

Reducing the accessory pulley diameter makes the belt drive the accessory spin faster for the same engine speed. The engine must supply power to drive that accessory, and power equals torque times angular speed. If the accessory torque stays the same but its speed goes up, the power the engine must provide to run the accessory increases. That extra power draw shows up as parasitic drag, so parasitic drag increases when you decrease the pulley diameter.