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The high-pressure direct injection (HPDI) of natural gas (NG) permits diesel engines to retain their high fuel economy while reducing regulated emissions. In the work presented in this paper, directly injected natural gas is ignited by pilot diesel fuel, and both fuels are injected through a single injector. The injector concept is discussed, along with the description of the instrumented Detroit Diesel two-stroke 6V-92TA DDEC II engine used for the experiments. Measurements of the performance and emissions with the HPDI of NG confirm the retention of the high efficiency of the diesel engine and demonstrate reductions in nitrogen oxide (NOx) emissions near 50% at high load using the same injection timing as for diesel fueling. Methane (CH4) and non-methane hydrocarbon (nmHC) emissions were found to be as low as those measured for diesel fueling at high loads, but were higher at low load operation. The gas injection pressure was found to affect the low-load emissions.

A Cummins C8.3 heavy-duty engine has been modified for operation on propane. The engine is spark ignited with a unique combustion chamber design to allow operation at lean mixtures to provide low emissions. The engine uses a dedicated microprocessor control system that provides ignition timing, fuel injection quantity and timing, and engine speed governing functions. The controller also uses adaptive learning to speed up its response. A special turbocharger with integral wastegate gives the required boost and control over its operating range. The engine produces 187 kW at 2100 rpm with low fuel consumption and exhaust emissions. The engine is demonstrated in a heavy-duty truck used for propane delivery. In order to fit a confined engine compartment, the new fuel system was designed to fit into the same envelope as the existing diesel engine.

A Kenworth T800 heavy duty dump truck operating on compressed natural gas has been in service with the city of Surrey, British Columbia. The truck uses a Cummins L-10-300G engine, a dedicated spark ignition engine. Fuel is stored in Dynetek high capacity cylinders, and a data logging system is fitted to monitor performance and fuel consumption of the truck. The truck is used in municipal service moving gravel and asphalt to work sites. A typical day's use is about 200 km. The truck has been modified significantly throughout the project. A stoichiometric natural gas engine has been replaced with a lean burn engine and the fuel capacity has been increased. One of the key findings in the demonstration has been that fueling stations must have their storage sized to the fuel capacity of the largest vehicle in order to allow reasonable refueling times.