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Heavy-duty diesel engines for transit bus applications are having to meet increasingly stringent emission standards. The new engines are significantly cleaner than they were just a few years ago. However, due to the long life of transit buses in Ontario (18 years), many buses still in service are powered by older engines which produce greater amounts of regulated exhaust emissions. The Ottawa-Carleton Regional Transit Commission (OC Transpo) has an interest in reducing emissions from older transit buses in their fleet. Eight Donaldson particulate trap systems were installed on transit buses. The purpose of the work, involving four different bus/engine combinations, was to assess the practicality and benefits of particulate traps in transit applications. This paper discusses the demonstration of diesel exhaust particulate traps in Ottawa-based transit buses.

Emissions from heavy-duty diesel vehicles have come under increased scrutiny with passage of the U.S. Clean Air Act Amendments of 1990. Methanol (M100) is seen as an important option for operators of transit fleets given the fuel's liquid nature and relative availability. This paper presents the results of a 36-month demonstration of a fleet of six methanol-powered transit buses equipped with DDC 6V-92TA engines. The engines were delivered in 1991 and were the first batch of Detroit Diesel engines certified to meet 1991 clean air standards. A similarly equipped control fleet of six diesel buses was tracked simultaneously. This paper includes an evaluation of bus operating data and emissions. Data such as fuel and oil consumption were collected along with a complete list of maintenance actions on both fleets. Chassis dynamometer emissions testing was carried out by Environment Canada at their River Road (Ottawa) test facility.

A 261 kW (350 hp) spark-ignited, turbo-charged and aftercooled Cummins “Big Cam” propane engine was developed and tested for class 8 truck application. Two propane engines were operated in line-haul service for a total of 33 months and almost 350 000 kilometres (217 480 miles). A diesel-powered tractor, in similar service, was monitored for comparison. Fuel economy, oil consumption, maintenance, drivers' comments, and engine refinements were fully documented. Propane fuel economy averaged 94 L/100 km (2.5 mpg), relative to 45 L/100 km (5.2 mpg) with the diesel. Overall reliability was good and driver acceptance excellent; however, further refinements, especially in the turbocharger, ignition, and cooling system, are required to compete with the modern diesel.