Development of a Heavy-Duty Engine Test Cycle Representative of On-Highway Not-To-Exceed Operation

Abstract

This paper describes the development of an engine test cycle that is representative of the real-world heavy-duty engine activity in the not-to-exceed (NTE) zone of operation. The test cycle is intended to provide an in-laboratory verification capability to determine if an engine exceeds the in-use emissions standards. By simulating the real-world driving pattern of the vehicle the test cycles provide the most realistic estimation of emission levels in the NTE zone of operation. It is well recognized that traditional laboratory test cycles do not provide an accurate representation of a vehicle's operation on the road under present-day driving conditions. This cycle was developed by collecting and analysing engine activity data and statistical information on heavy-duty vehicle use for different applications under real-world conditions. A test vehicle instrumented with the West Virginia University mobile emissions measurement system (MEMS), a portable on-board tailpipe exhaust emissions measurement system, was used to obtain engine operating conditions, vehicle speed, and in-use brake-specific emissions of CO2 and NO x. The vehicle was tested on specific routes, which included a mix of highway and city driving patterns. The speed and torque points were normalized according to procedures described in the Code of Federal Regulations (CFR) Title 40, Part 1065. A representative transient cycle that was developed has been used to conduct emissions tests on heavy-duty diesel engines, and serves to characterize NO x emissions during the NTE operation. This characterization will aid in-laboratory testing and provide a better understanding of the emissions behaviour during on-road NTE operation, electronic control module calibrations, and engine development. The results indicate that the on-highway NTE cycle called the ‘WVU NTE cycle’ produced emissions results that were within ±1 per cent of those produced during an on-road test.