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The Detroit Diesel 6V-92TA engine has been redesigned to run on alcohol fuels to meet 1991 urban bus emission standards. A prototype engine was tested over the EPA transient procedure, using mixtures of methanol, ethanol (with and without water), gasoline, and ignition enhancer. Regulated and selected unregulated emissions were measured. Organic material hydrocarbon equivalent (OMHCE) emissions were significantly above the hydrocarbon emission standard; however, emissions of CO and NO, were below the 1991 emission standards for the fuel combinations used. Particulate emissions were close to the 1991 urban bus emission standard for some configurations. The method used for calculating OMHCE emissions when ethanol was used is also given.

Several diesel fuel properties have been identified as having significant effects on diesel engine emissions. For heavy-duty diesel engines, fuel properties of aromatics, back end volatility (represented by the 90 percent boiling point), and sulfur were examined in a previous CRC VE-1 study in which reductions in all three properties decreased regulated emissions to varying degrees. Aromatic levels and cetane numbers were generally correlated in the previous study, so variation in emissions due to “aromatics” could not clearly be assigned to variation in aromatic levels alone. To separate the effects of aromatics and cetane number, a fuel set with controlled variation in aromatics and cetane number was developed, including the use of ignition improver to increase the cetane number of selected fuels. The fuel set was used in a 1991 Prototype DDC Series 60 heavy-duty diesel engine to examine regulated emissions over EPA transient cycle operation.