Development of Three Cylinder CNG Engine for LCV Application

Compressed Natural Gas (CNG) engine has proved itself to be worthy replacement for diesel in heavy commercial and passenger transport application all over the world. In India, infrastructure development of CNG distribution and stringent emission regulations have increased the interest shown by Original Equipment Manufacturers (OEM) to concentrate to development of CNG vehicles in every segment. Indian cities are fighting pollution due to high vehicle density and since contribution of light commercial vehicles in intra city application is significant, application of dedicated CNG vehicle has been made mandatory. This paper discusses the development of dedicated CNG engine using injection technology meeting the upcoming BS-IV norms. The primary modifications made are in the cylinder head, piston, intake and exhaust systems. The engine being developed for commercial application, the best in class fuel economy is of prime focus. Throttle body options were tried to ensure a “Car - like” drive ability. Keeping the market segment's price sensitivity in mind various cost reduction ideas have been implemented from the base diesel version to reduce the differential cost. EMS system capable of meeting OBD-II and with improved safety improving logic has been developed. Optimization of calibration was done for air flow, fuel flow, ignition timing, spark energy, injection timing, and precise lambda control for achieving best compromise of performance and emission with lowest precious metal loading. Consistency checks and endurance testing will ensure repeatability and durability of the final engine and calibration. The improvements that can be done to further increase the thermal efficiency is also listed.