Abstract
Many vehicle systems simulations utilize engine maps constructed from steady-state dynamometer measurements to estimate exhaust temperature and emissions as functions of engine speed and load. Unfortunately, steady-state engine behavior is often significantly different from actual behavior under realistic driving conditions. This is particularly true for vehicles (e.g., electric hybrids) that undergo repeated engine shutdown and restart. We propose a methodology for estimating transient engine exhaust properties based on corrections to steady-state maps. We have implemented our methodology in the Powertrain Systems Analysis Toolkit (PSAT) and use this implementation to demonstrate good agreement with experimental measurements for both a light-duty diesel and a flex-fuel gasoline/ethanol engine. We also recommend specific procedures for setting key parameters required by our methodology and suggest possible directions for further improvements.