Question 50 UFIV01 - Chief Engineer - UFIV

The Correct Answer is C ### Explanation for Option C (Correct) Option C is correct because the maximum restriction (pressure drop) across an air intake filter occurs when the engine is demanding the maximum amount of air. This maximum demand condition is achieved when the engine is operating at its **rated RPM** (or near maximum RPM) and is under **full load**. The function of the restriction indicator is to measure the vacuum or pressure drop in the air duct between the clean side of the filter and the turbocharger inlet. This pressure drop is directly proportional to the volume flow rate of air being pulled through the filter. If the filter is clogged, the restriction will increase, potentially leading to reduced engine performance (e.g., higher exhaust temperatures, reduced power, or poor combustion). Therefore, filters must be evaluated under the most demanding conditions to ensure they can adequately supply air when the engine needs it most, which is at full power output. ### Explanation for Other Options (Incorrect) **A) The engine should be running at idle RPM with minimal load (propulsion clutch engaged).** Incorrect. At idle RPM and minimal load, the engine's air consumption is at its minimum. The resulting restriction reading will be very low, even if the filter is significantly clogged. This low reading would not accurately reflect the restriction the engine would experience under high-power conditions, making the evaluation useless for determining the filter's operational limits. **B) The engine should be running at rated RPM with no load (propulsion clutch disengaged).** Incorrect. While the engine is running at high RPM (rated speed), the *no-load* condition means the fuel injection rack is only delivering enough fuel to overcome internal friction. The engine's total airflow demand is significantly lower than it would be under full load, as the turbocharger is not producing maximum boost pressure. This reading would still underestimate the true maximum restriction. **D) The engine should be running at idle RPM with no load (propulsion clutch disengaged).** Incorrect. This represents the absolute minimum air demand condition, similar to Option A. The restriction reading would be negligible and provide no meaningful data regarding the filter's ability to support full-power operation.