Knowledge Bank

The EcoCAR challenge is a three year competition with a goal of re-engineering a 2009 General Motors crossover utility vehicle to improve vehicle emissions and fuel economy, while maintaining drivability and consumer acceptability. Ohio State’s team has selected a plug-in hybrid electric vehicle (PHEV) architecture with a 1.8 L CNG Honda engine as the auxiliary power unit. The Honda engine is converted to run on E85 fuel, which requires the engine control software to be rewritten. The purpose of this research is to write a feed forward air/fuel ratio (AFR) control algorithm to better manage fuel injection during transient engine events. AFR control has a major impact on engine fuel economy and tail pipe emissions. This research investigates the accuracy of using a dynamic intake manifold filling and emptying model coupled with a linear approximation of the Taylor Series expansion to predict air flow forward in time. To better estimate air flowing passed the throttle plate and into the intake manifold, a quasi-static effective area map of the throttle was created. The control algorithm uses the throttle effective area map to improve the accuracy of air flow estimation into the intake manifold because the MAF sensor is not a reliable flow meter during transient engine events. It also uses a feed forward volumetric efficiency map to predict mass air flow exiting the intake manifold. It was found that by using feed forward control software and empirical engine maps to predict manifold air pressure forward in time, a better estimate of mass air flow entering the cylinder was achieved. The creation of this software allows the EcoCAR vehicle to better maintain a stoichiometric AFR during transients, which reduces tail pipe emissions species, including NOx, CO, and unburned Hydrocarbons.