Using In-Cylinder Pressure Measurements for SI Engine Control

Per Tunestal, Mechanical Engineering, UC Berkeley

The traditional approach to Air/Fuel-ratio control is a SISO approach where the input is injection time per cycle, and the output is a rich/lean signal from the oxygen sensor in the exhaust. Mixing of exhaust gases from different cycles and the inherent time delay from measuring in the exhaust impose severe bandwidth limitations on the closed loop system. This bandwidth limitation can be overcome by measuring the in-cylinder pressure during combustion, and from this extracting desired parameters such as actual A/F-ratio.