Decrease the crankshaft pulley diameter.

Decrease the crankshaft pulley diameter.

• A. To Increase Parasitic Drag
• B. To Decrease Parasitic Drag
• C. No effect on parasitic drag
• D. Has no impact on drag

Answer: (B)

Lowering the crankshaft pulley diameter reduces parasitic drag because it makes the belt-driven accessories spin more slowly at the same engine speed. With a smaller crank pulley, the accessories (alternator, power steering pump, A/C compressor, etc.) take longer to reach their driven speeds, so the engine doesn’t have to supply as much power to keep them running. That drop in power draw from the accessories means less parasitic loss, freeing more horsepower for the wheels. If the pulley were larger, the accessories would run faster and demand more power, increasing drag. There would be no drag only if the accessories didn’t draw power at all, which isn’t the case, so the diameter does impact drag.

Lowering the crankshaft pulley diameter reduces parasitic drag because it makes the belt-driven accessories spin more slowly at the same engine speed. With a smaller crank pulley, the accessories (alternator, power steering pump, A/C compressor, etc.) take longer to reach their driven speeds, so the engine doesn’t have to supply as much power to keep them running. That drop in power draw from the accessories means less parasitic loss, freeing more horsepower for the wheels. If the pulley were larger, the accessories would run faster and demand more power, increasing drag. There would be no drag only if the accessories didn’t draw power at all, which isn’t the case, so the diameter does impact drag.