Question 17 AEL01 - Assistant Engineer - Limited

The Correct Answer is C **Explanation for Option C (Correct Answer):** The purpose of measuring the air intake restriction is to determine if the filter is becoming clogged, which impedes the engine's ability to ingest the necessary volume of air. This problem becomes most pronounced when the engine demands the maximum possible airflow. * **Rated RPM and Full Load:** When a turbocharged engine is running at its rated (maximum continuous) RPM and under full load, the turbocharger blower spins at its highest speed and is attempting to draw the largest volume of air possible through the intake system. This creates the maximum pressure differential (restriction) across the air intake filter. * **Evaluation Criterion:** Restriction indicators (or gauges) are calibrated to monitor this maximum restriction limit. To accurately assess whether the filter needs cleaning or replacement based on the manufacturer's specified limit, the measurement *must* be taken under the condition that generates the highest stress on the filter—i.e., maximum airflow demand. **Explanation for Incorrect Options:** * **A) The engine should be running at idle RPM with no load (propulsion clutch disengaged):** At idle, the engine demands minimal airflow. The turbocharger operates slowly, resulting in a very low intake restriction reading. This reading would not accurately reflect the actual maximum restriction capacity of the dirty filter and would not be useful for determining if the filter limit has been reached. * **B) The engine should be running at idle RPM with minimal load (propulsion clutch engaged):** Similar to option A, idle speed generates very low airflow demand and low intake restriction. Even with minimal load, the restriction level is far below the maximum needed for a reliable assessment. * **D) The engine should be running at rated RPM with no load (propulsion clutch disengaged):** While the engine RPM is high, without a significant load, the engine's demand for fuel and corresponding air (boost pressure) is reduced. The turbocharger will not be operating at its peak speed or creating the maximum air mass flow rate, meaning the restriction measurement will be artificially lower than the maximum restriction the filter would experience during normal operational demands.