Abstract
A first order analytical vehicle fuel consumption model is developed based on an input/output description of engine fuel consumption, also known as the Willans line. At the low engine speeds typical of most driving, the fuel consumed per cycle is primarily a function of load and not speed. It is then effective to express it as fuel energy per cycle normalized for displacement, which puts it in units of Mean Effective Pressure (MEP). At light to medium loads, the Fuel MEP is a linear function of load, the slope reflecting the indicated efficiency, and the offset reflecting engine combustion, friction, and pumping losses. The model breaks down the slope and offset in terms of established engine properties. A parametric analytic model of vehicle fuel consumption is developed, in terms of basic vehicle, powertrain and engine properties. The model provides a good description of the highway fuel consumption of the US conventional, automatic transmission, light duty fleet.
KEYWORDS – SI Engine, Vehicle Fuel Consumption, Model, Willans Line