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In an effort to demonstrate the ability of portable, on-board emissions monitoring systems to collect data on a large number of vehicles in a short period of time, 40 heavy-duty diesel trucks were tested in 2.5 days using a portable, on-board system. The trucks were randomly recruited at a Tulare, CA rest area, and subjected to idling and opacity tests. 21 of these trucks were also tested on the road. The equipment was well received by the drivers. Average NOx emissions were 157-188 grams per gallon of fuel during idle and 112 g/gallon during cruise. At least one case suggesting a NOx “defeat” strategy was observed. Elevated PM emissions during deceleration, attributed to the use of engine brake, were observed on one third of the trucks. Results show that stationary idle data can be used to identify trucks with high NOx during acceleration, but not necessarily all the trucks with high NOx during cruise could be identified using idle measurements.

This paper describes attempts to determine stabilized emissions of non-road engines without waiting for stable emissions values to be reached, with the goal to shorten laboratory testing time and/or to use real-world, in-service data featuring limited segments of steady-state operating conditions. The emissions from non-road engines are often evaluated and reported in steady-state operating conditions. Many larger engines are tested in the field, due to impracticality of dynamometer testing, resulting in practical limits for testing time at constant operating conditions. With lower fractions of elemental carbon (black soot) in the particulate matter and increased deployment of catalytic aftertreatment devices, longer times are required for reaching stable values. This work seeks to infer stabilized emissions values from limited length segments of unsteady but converging data.

The paper focuses on portable “on-board” instrumentation and methods for evaluation of exhaust emissions from scooters and various small machinery under real-world driving conditions. Two approaches are investigated here. In one, a miniature on-board system mounted on the equipment itself performs online measurements of the concentrations of the pollutants of interest (HC, CO, CO2, NOx, some property of particulate matter), and measurement or computation of the intake air flow. This approach has been used on a 50 cm3 scooter fitted with a 14-kg on-board system and driven on local routes. Measured concentrations of gaseous compounds, particle mass and total particle length were multiplied with the corresponding intake air flow computed from measured engine rpm, intake air manifold pressure and temperature. In the second approach, a full-flow dilution tunnel, gas analyzers and particle measurement or sampling devices are mounted on an accompanying hand cart or vehicle.