Question 32 3AE01 - Third Assistant Engineer

The Correct Answer is A ### Explanation for Correct Option (A) **A) The filter element is severely restricted with dust and requires immediate replacement.** The measurement being taken is the vacuum (negative pressure) in the air duct between the air filter and the turbocharger inlet. This vacuum exists because the turbocharger blower is drawing air through the filter, which inherently offers resistance. 1. **Baseline Resistance:** A reading of $10"$ of water column (negative) is established as the normal baseline resistance for a clean, properly sealing filter element at full load and rated RPM. This $10"$ represents the standard pressure drop required to move the necessary volume of air through the clean filter. 2. **Increased Resistance:** A reading of $20"$ of water column (negative) means the vacuum (suction pressure) required to pull the same volume of air is now twice the normal baseline. 3. **Indication:** Increased vacuum, when the engine RPM and load (and thus the air demand by the turbocharger) remain constant, directly indicates increased resistance to airflow. The primary cause of increased resistance in a dry-type filter element is the accumulation of contaminants (dust, dirt, etc.), which restricts the flow path. Doubling the baseline vacuum level usually signifies a critically restricted filter element that is severely limiting the air supply to the turbocharger and engine, leading to potential issues like power loss, increased exhaust temperature, poor combustion, and reduced efficiency. Therefore, immediate replacement is required. ### Explanation for Incorrect Options **B) The filter element is being slightly bypassed due to an improper seal and can be ignored until time is available for re-seating.** * A filter bypass (improper seal) would allow air to leak around the element, reducing the total resistance the engine sees. This would cause the measured vacuum to **decrease** (i.e., read less than $10"$), not increase to $20"$. **C) The filter element is being severely bypassed due to an improper seal and should be immediately re-seated.** * Similar to option B, a severe bypass would drastically **decrease** the measured vacuum reading, potentially bringing it close to $0"$, as air would be drawn in with minimal restriction. It would not cause the vacuum to double. **D) The filter element is slightly restricted with dust but does not yet require replacement.** * A reading of $20"$ of water column is double the clean baseline of $10"$. In filtration diagnostics, a $100\%$ increase over the clean filter pressure drop typically signifies a severe or critical restriction, not a slight one. A slight restriction might register $11"$ or $12"$. A reading of $20"$ indicates a severe air starvation condition that demands immediate attention and replacement.