MAN Methanol Engines For Use In Buses

Originally the idea of using methanol as a fuel came into the limelight on the strength of basic considerations in respect of long-term conservation of energy in the transport sector. In recent times, however, the environmental aspects of methanol have taken precedence over that original goal. It is particularly in the range of heavy-duty commercial vehicles that methanol results in substantial reductions in particulate and Nox emissions. At MAN, the development of methanol engines is based on the Diesel engine. The problem associated with the poor self-igniting quality of methanol is solved in this case by high-voltage spark ignition. Such features as direct single-jet injection, unthrottled air intake and high compression have been taken over from the Diesel. The result is a stratified-charge engine with external ignition - also known as a “spark-assisted Diesel”. The system has been adopted for naturally aspirated and turbocharged intercooled versions of our 11.4 liter 6-cylinder engines which are suitable for underfloor installation in regular line., service buses. Both engines are equipped with oxidation converters and satisfy the recommended 1991 U.S. emission limits for city buses - limits which, especially with regard to particulates, can barely be reached even by Diesel engines equipped with exhaust filters. The energy consumption is comparable to that of the Diesel engine. At present, 12 naturally-aspirated 150 kW engines and 10 turbocharged 200 kW engines are in regular bus line service.