Right-Sized Propulsion Power Means Higher Mileage and Lower Tailpipe Emissions

Truck and car manufacturers are required to satisfy certain emission standards while driving regulatory prescribed driving cycles on a vehicle chassis dynamometer. In India, the requirement is to use the regulatory Modified Indian Driving Cycle (MIDC), derived from the European Driving Cycle. The MIDC is a modal driving cycle with protracted periods at constant speed and uniform acceleration and deceleration patterns. It does not emulate typical road driving. In this study we instrument vehicles with off-the-shelf On-Board-Diagnostics (OBD) loggers to record actual drive data. The recorded vehicle speed profiles are then used as inputs for the vehicle simulation model we develop. The simulation model uses vehicle speed as an input and then calculates power required at the wheel, gear box, and Internal Combustion Engine (ICE) for the vehicle to achieve the measured speed profile. We use Willans Approximation to model the ICE fuel flow based on torque and speed. The simulation model is calibrated using data from a vehicle instrumented with an external AFR sensor, tested on a vehicle chassis dynamometer. Based on this study, for a typical mid-size car equipped with a 50kW internal combustion engine, we find that the average propulsion power required is only 5kW. We conclude that it is possible to significantly reduce fuel consumption and emission of a standard vehicle once retrofitted with a torque assist system sized to match the average propulsion power requirement.