Reducing Locomotive Idle Fuel Consumption and Exhaust Emissions by Applying an Auxiliary Power Unit (APU)

This paper documents results of fuel consumption and exhaust emission tests performed on a 1,500 kW EMD GP38-2 locomotive equipped with an auxiliary power unit (APU) designed to minimize main engine idling time by providing stand-by services normally provided by the main EMD 16-645-E engine at idle. The purpose of these tests was to perform an evaluation of the exhaust emissions and fuel consumption of both the EMD 16-645-E engine and the APU. The APU diesel engine was a 2.0L, 4-cylinder, turbocharged, Kubota model V2003-TEBG rated at 30.6 kW. The APU was tested using an external load box over a range of load conditions, ranging from unloaded (0 kW) through 16 kW, which was the maximum APU load expected as installed in the locomotive. Fuel consumption and exhaust emissions are compared between an idling EMD 16-645-E engine and the APU engine at a “typical” stand-by condition with the coolant and lubricating oil heaters operating and the locomotive control cab air conditioner turned off. Test results showed that the APU fuel consumption and exhaust emissions are dramatically lower than the idling EMD locomotive engine. Because the APU is designed to automatically start and stop as a function of the locomotive water temperature, and therefore operates only a portion of the time that the EMD engine would otherwise be idling. Reductions in fuel consumption and exhaust emissions over an extended period of time would be even more dramatic.