An underdrive pulley reduces __________.

An underdrive pulley reduces __________.

• A. Compressor load
• B. Engine torque
• C. Fuel economy
• D. Parasitic drag

Answer: (D)

Parasitic drag from engine accessories is reduced. Slowing the belt-driven components (like the alternator, power steering pump, and AC compressor) means they draw less power from the crankshaft. That lowers the engine’s wasted energy spent on accessory work, which is exactly parasitic drag. While the compressor’s load is part of that drag, the broader effect is the overall reduction in parasitic drag. It doesn’t directly reduce engine torque itself, and any fuel-economy benefit is a downstream result of having less parasitic loss.

Parasitic drag from engine accessories is reduced. Slowing the belt-driven components (like the alternator, power steering pump, and AC compressor) means they draw less power from the crankshaft. That lowers the engine’s wasted energy spent on accessory work, which is exactly parasitic drag. While the compressor’s load is part of that drag, the broader effect is the overall reduction in parasitic drag. It doesn’t directly reduce engine torque itself, and any fuel-economy benefit is a downstream result of having less parasitic loss.