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Two Computer models were used to study abnormal combustion in a crankcase-scavenged two-stroke engine fueled on methanol. Experimental studies had shown that the octane rating of methanol in this engine was lower than that of gasoline when compared to known reference fuels. Through computer modeling, the abnormal combustion was shown to be a combination of auto and surface ignition resulting from high intake charge temperatures and high residual fractions inherent in crankcase-scavenged two-stroke engines. Precursors of knock were also shown.

California cars operating on higher-sulfur gasolines than prevalent in California should not result in “false tripping” of the on-board catalyst monitoring system. The monitoring systems to be used on California low-emission vehicles will be unable to detect the small extra amount of loss in catalyst effectiveness that might be caused by higher sulfur levels outside of California. Testing of a mocked-up ultra low-emission vehicle (ULEV) conducted by the California Air Resources Board (CARB) confirms that on-board monitoring systems are not tripped even by high sulfur levels (800 ppm). An independent U.S. Environmental Protection Agency (EPA) assessment also agrees that “false tripping” of monitoring systems of the California cars is not expected to be a problem either for California cars operated temporarily outside of California or for California-type cars sold in other states.

Technologies and incremental costs for meeting the proposed 2004 US emissions standards for heavy-duty diesel engines are discussed in this paper. Manufacturers will most likely use a combination of technologies including reoptimized combustion chambers, fuel systems, air handling systems, electronic controls and aftertreatment. First year production incremental costs are estimated to range from between $257 and $467 to meet the new standards.