Catalytic Exhaust Emission Control System For City Buses With Liquified Petroleum Gas Engines

The low price of LPG for public transport in Austria as well as the low level of the exhaust emissions of the pollutants CO, HC and particulates of LPG operated spark ignition engines were the main reasons for which the Vienna Transport Authorities started to change their diesel bus fleet to LPG-operation already in 1963. As a consequence of the intensive discussion regarding ecological damage during the past years, the Vienna Transport Authorities requested an effective emission control system to reduce the NO_x-emissions. The high efficiency and the good attributes of the additivefree Liquefied Petroleum Gas for a catalytic emission control system led ÖAF-GRÄF & STIFT to the decision of developing an oxygen sensor controlled LPG-engine with a metallic three-way catalytic converter.