Converting a small car to LNG: what are the problems and what can it do for economy and emissions

A two liter compact car originally designed to run on gasoline was converted to run on LNG. Comparative measurements of fuel economy and exhaust emission were made for the same car running on each fuel under normal on-the-road and simulated taxi service. When tuned to its maximum economy configuration, the LNG car gave significant improvements in fuel economy when expressed on an energy basis. For inter-urban journeys the savings would be of the order of 5% and for taxi type service in excess of 20%. When set for maximum economy the LNG car gave significantly lower emissions of CO and hydrocarbons than its gasoline counterpart. Emissions of NO/sub x/ were, however, higher with LNG than with gasoline. A tenfold reduction in NO/sub x/ emissions could be obtained by re-tuning the LNG engine to run at air/fuel ratios up to 30:1. Hydrocarbon emissions with this configuration were, however, quite high and would require supplementary means of control. When tuned to operate at very weak mixtures the car remained quite driveable but was 10 to 15% less economical than when tuned for maximum economy.