Question 62 QMED03 - Oiler

The Correct Answer is B **Explanation for B (power the turbocharger):** The primary and essential function of the exhaust system in a turbocharged diesel engine is to channel the high-temperature, high-pressure exhaust gases from the cylinders directly into the turbine housing of the turbocharger. The energy contained in these moving exhaust gases spins the turbine wheel. This spinning turbine is mechanically connected by a shaft to the compressor wheel, which draws in and compresses fresh intake air for the engine. Therefore, the exhaust gases effectively provide the kinetic energy (power) needed to drive the turbocharger. **Explanation for Why Other Options Are Incorrect:** * **A) power the aftercoolers:** Aftercoolers (or intercoolers) are typically passive heat exchangers that cool the compressed intake air. They do not require external power from the exhaust system to function, nor does the exhaust system directly supply power to them. * **C) reduce the cylinder scavenge effect:** "Scavenging" refers to the process of using incoming fresh air to push out residual exhaust gases during the overlap phase of valve timing. A well-designed exhaust system, especially when coupled with a turbocharger that may create some back pressure, can actually optimize the *efficiency* of scavenging, but its function is not primarily to *reduce* it. In fact, excessive back pressure (which is part of the turbocharging process) can sometimes slightly hinder perfect scavenging, but this is a trade-off for the massive benefit of forced induction. * **D) cool the turbocharger:** While the exhaust gases heat the turbine side significantly, the exhaust system's function is to *drive* the turbocharger, not to *cool* it. Turbochargers are primarily cooled by circulating engine oil and/or engine coolant (water-cooling), not by the flow of the hot exhaust gases themselves.