Optimizing Closed Loop Air Mass Control in Naturally Aspirated Engines: A Differential Pressure Sensor Approach to meet BS6 Emission Norms

In order to meet stringent emission targets and to achieve better fuel efficiency, closed loop air mass control strategies have become essential across all vehicle segments. Closed loop air mass control mandates measuring fresh air mass entering the engine combustion chamber. However, in Naturally Aspirated (NA) engines, while measuring air mass using conventional methods such as Hot Film Air mass (HFM) sensor, heavy pulsations in the Air-intake results in errors which would impact closed loop air mass control and lead to inconsistencies in emissions. To address this issue, we studied different approaches using HFM sensor with Resonator, differential pressure sensor across the intake air filter and Lambda based air mass control. Based on this empirical study we found that modelling air mass with differential pressure sensor using Bernoulli’s principle (Flow rate ∝ √Differential pressure) results in higher accuracies compared to conventional methods. This solution gives accurate, cost-effective Air mass modelling in single or two cylinder naturally aspirated engines which are prevalent in Light Commercial Vehicle (LCV) segment for BS6 market. The research provides a detailed explanation of the Air mass modeling approach using Delta-P sensor across Intake Air-filter and its implementation, along with the issues and mitigation measures involved.