Real-Time Combustion Phase Optimization of a PFI Gasoline Engine 2011-01-1415

Combustion control is assuming a crucial role in reducing engine tailpipe emissions and maximizing performance. The number of actuations influencing the combustion is increasing, and, as a consequence, the control parameters calibrations is becoming challenging.

One of the most effective factors influencing performance and efficiency is the combustion phasing: gasoline engines Electronic Control Units (ECU) manage the Spark Advance (SA) in order to set the optimal combustion phase. SA optimal values are usually determined by means of calibration procedures carried out on the test bench by changing SA values while monitoring Brake and Indicated Mean Effective Pressure (BMEP, IMEP), Brake Specific Fuel Consumption (BSFC) and pollutant emissions. The effect of SA on combustion is stochastic, due to the cycle-to-cycle variation: the analysis of mean values requires many engine cycles to be significant of the performance obtained with the given control setting. Usually, the optimization process is carried out off-line, based on the data sampled on the test-bench.

This paper presents the application of a new calibration concept, with the objective of improving the robustness of performance analysis, while reducing the test time. The approach is applied to a simple calibration problem, where a single input factor (SA) is tuned taking into account two issues: IMEP maximization and knock limitation. The paper shows how the methodology can be extended to multiple objective and multi-input optimization problems.