LPG: Pollutant emission and performance enhancement for spark-ignition four strokes outboard engines

Experimental research into the use of LPG in spark-ignition outboard engines is presented. Two different outboard engines were adapted for operation with bottled LPG dosed in gaseous form. The aim of the study was to determine the basic parameters and quantify the emission index for carbon monoxide, unburned hydrocarbons, and nitric oxides when LPG is used instead of gasoline.The results obtained indicate that with the use of LPG, specific fuel consumption and CO emissions were much lower without noticeable power loss while HC emissions are shown to be little affected by fuel substitution. In contrast, NOx emissions were higher, but could be kept below current and future emission limits.