Real-world testing of heavy duty vehicles for emissions and fuel economy

Current heavy duty engine testing is performed exclusively on engine dynamometers. The limitations of this method to obtain detailed emission data for heavy duty vehicles operating in the field are widely known. The wide variety of vehicles into which an engine type may be fitted and the disparate operating conditions that the vehicle is then subject to, mean that the real environmental impact of heavy duty vehicles can rarely be accurately established. The new Variable Temperature Emissions Chamber (VTEC) facility built at Millbrook allows chassis dynamometer testing of all manner of road vehicles from standard passenger cars right up to Double Decker Buses. This enables accurate emissions data to be measured for specific vehicles in their real operating environments. The facility is equipped to simulate ambient temperatures from -30 degrees C to +40 degrees C with a high volume, speed tracking air flow. Driving cycles have been developed for buses and trucks, both from detailed on-road data logging and from simulated operations. This paper describes the test methods now available to engine and vehicle manufacturers and vehicle operators to enable accurate emissions and fuel economy data to be established for all typical road vehicles. The benefits to all these parties and to fuel and catalyst suppliers are illustrated with emissions data showing the techniques used and the results of product development to reduce heavy duty vehicle emissions in the field.