IP engineers specified new catalysts, to reduce emissions, and designed and specified new turbochargers and valve train, to increase performance and response. They worked with Bentley and the engine management supplier to develop a new engine control unit (ECU), which they calibrated using MATLAB®, Simulink®, and Model-Based Calibration Toolbox™.
Working in Simulink, IP engineers created a dynamic model of the engine's entire valve train. They used a combustion model to simulate the forces exerted on the valves by cylinder pressure.
They validated the model by using MATLAB to process data gathered from an existing engine fitted with strain-gauged pushrods. They first compared results visually. Later, they performed a more detailed verification, using MATLAB to compare Simulink results with the measured data.
The IP team used the model to evaluate several camshaft profiles over a range of speed-load conditions. The redesigned camshaft based on these simulations delivered immediate emissions and power-output improvements the first time it was installed.
Next, the team re-optimized the calibration. Using Simulink and Model-Based Calibration Toolbox, they developed statistical models of key engine responses from spark-sweep mapping data. They used those models with a Simulink implementation of the ECU strategy to calibrate the torque, exhaust gas temperature, and air-charge models.
Once they had mapped the ECU, the team could optimize the engine behavior to reduce emissions during the catalyst light-off period. They focused on optimizing the engine running during the first 30 seconds after a cold start. They used parameterized Simulink models of the inlet manifold "lost fuel" characteristics and "wall wetting" dynamics, together with data from actual tests, to tune the cold start and drive-away calibration. A design of experiments was performed using Model-Based Calibration Toolbox to optimize the pre-light-off emissions from the engine.
The design changes developed by IP are currently in production in the 2007 Bentley Arnage.