Which component is listed as contributing to engine losses in net horsepower?

• A. Alternator
• B. Piston rings
• C. Crankshaft
• D. Transmission

Answer: (A)

Net horsepower reflects the engine’s gross power minus power taken away by accessories and other parasitic losses. The alternator is a prime example of a parasitic load: it must be driven by the engine to generate electrical power for the vehicle, charging the battery and running electrical systems. That power draw reduces what the engine can deliver for propulsion, so the alternator is listed as contributing to engine losses in net horsepower.

Piston rings and the crankshaft do contribute to internal engine friction, but their losses are part of the engine’s normal mechanical efficiency and aren’t singled out as external losses in the net horsepower figure. The transmission, being in the drivetrain downstream of the engine, doesn’t count as an engine loss in net horsepower.