What is the maximum inlet restriction permitted on a diesel engine air filter?

What is the maximum inlet restriction permitted on a diesel engine air filter?

• A. 25" H20
• B. 5" H20
• C. 50" H20
• D. 10" H20

Answer: (A)

Airflow must be sufficient for the engine to run well, so there’s a maximum allowable pressure drop across the air filter. This restriction is measured in inches of water (in H2O). When the filter gets dirty, the drop increases; once it reaches the specified limit, airflow is too restricted and performance suffers, so the filter should be serviced or replaced. For many diesel engines, the standard maximum is about 25 inches of water. The other values would indicate too little or too much restriction for normal operation, so they’re not used as the limit. Therefore, the maximum permissible inlet restriction is 25" H2O.

Airflow must be sufficient for the engine to run well, so there’s a maximum allowable pressure drop across the air filter. This restriction is measured in inches of water (in H2O). When the filter gets dirty, the drop increases; once it reaches the specified limit, airflow is too restricted and performance suffers, so the filter should be serviced or replaced. For many diesel engines, the standard maximum is about 25 inches of water. The other values would indicate too little or too much restriction for normal operation, so they’re not used as the limit. Therefore, the maximum permissible inlet restriction is 25" H2O.