Which energy source powers a turbocharger?

• A. Crankshaft power
• B. Electric motor
• C. Fuel flow
• D. Exhaust gases

Answer: (D)

Turbochargers harness energy from exhaust gases to drive the compressor. The hot, high-velocity exhaust leaves the engine and spins a turbine inside the turbocharger. That turbine is connected to a compressor on the same shaft, so as the exhaust energy spins the turbine, the compressor pushes more air into the engine, allowing more fuel to be burnt efficiently and increasing power. This use of exhaust energy is what makes turbocharging effective, since it recovers energy that would otherwise be wasted.

The other options don’t fit because a mechanically driven turbo (or supercharger) would rely on crankshaft power through belts or gears, not the exhaust stream. An electric motor could power an electric turbo system, but that’s a different configuration from a conventional turbocharger. Fuel flow supplies energy to the engine itself, not directly to spin the turbine. Therefore, exhaust gases provide the energy source for a turbocharger.