A technician is comparing forced induction systems on two reciprocating engines. Engine A uses a mechanically driven supercharger, while Engine B uses a turbocharger. Which statement correctly describes the mechanically driven supercharger?
- AIt is driven directly by the engine crankshaft through gears or a clutch, consuming engine power to compress the induction air
- BIt is used exclusively on turbine (jet) engines rather than reciprocating engines
- CIt is driven by exhaust gases passing through a turbine wheel, independent of crankshaft power
- DIt uses a wastegate valve to control the amount of exhaust gas diverted around the turbine
Show answer & explanationAnswer & explanation
Correct answer: A. It is driven directly by the engine crankshaft through gears or a clutch, consuming engine power to compress the induction air
A mechanically driven (gear-driven) supercharger obtains its power directly from the engine crankshaft, so it always consumes a portion of engine output to compress the induction air, whereas a turbocharger uses otherwise-wasted exhaust gas energy to spin a turbine that drives the compressor, and typically uses a wastegate to regulate boost.
Why the other options are wrong
- B. Superchargers are used on reciprocating engines; turbine engines have their own internal compressors, not add-on superchargers.
- C. This describes a turbocharger, driven by exhaust gas energy, not a mechanical supercharger.
- D. Wastegates are a turbocharger control feature, not part of a mechanically driven supercharger.
Supercharger vs Turbocharger
A supercharger is mechanically driven off the crankshaft and consumes engine power to boost induction pressure; a turbocharger uses exhaust gas energy through a turbine to drive the compressor without direct crankshaft power.
- Supercharger: gear/clutch-driven from crankshaft
- Turbocharger: exhaust-driven turbine wheel
- Turbocharger uses wastegate to regulate boost pressure
Memory trick: Supercharger borrows power from the crank; turbocharger recycles wasted exhaust.