Getting Performance without Sacrificing Economy or Emissions Control in a Heavy-Duty LPG Engine

Limited route service experience with a commercial 637 CID conversion of a gasoline engine indicated both its potential and the need for its optimization in order to take advantage of the unique characteristics of liquefied petroleum gas fuels. At the request of the Chicago Transit Authority, an engine-dynamometer study, with emphasis on fuel system-ignition relationships, was conducted at the Phillips Petroleum Co.'s Automotive Laboratories.

Dynamometer studies led to substantial improvement in fuel economy without depreciation of engine power. Cylinder head redesign by the engine manufacturer permitted lean mixture operation that reduced exhaust emissions to levels calculated to conform to the 1973 federal standards and 1973-1974 California Air Resources Board requirements for heavy-duty engines.