Last mile transportation is an important supply chain and transportation requirement for the movement of people and goods from a transport hub to a final destination in that area. In India this requirement is largely met by 3 wheelers and small 4 wheelers (below 1 ton payload). Greaves cotton Ltd. (GCL) has played an important role for last mile transportation solutions in India by developing suitable engines for the above category vehicles. GCL is already supplying single cylinder air cooled 400 cc diesel / CNG, 435 cc & 510 cc diesel and 510 cc water cooled CNG BSIII engines for 3 wheeler applications. Single cylinder water cooled 510 cc and 611 cc BSIII diesel engines are being supplied for small commercial 4 wheeler applications.In India, BSIV emission norms are in place since April 2010 in metro cities for 4 wheelers. CNG network is well established in most of these cities. Hence to serve this market, the CNG engine variant development of the 611 cc diesel BSIII engine was initiated.At present ECU based close loop CNG port injection technology is used in multi-cylinders engines for car and commercial vehicle applications. On the other hand, single cylinder engines with venturi based open / close loop systems are being used for 3 wheeler vehicles. This is a first of its kind of efforts which combines the ECU based port injection as well as electronic throttle body (ETB) technology and various sensors for a single cylinder engine to make it suitable for small 4 wheeler applications.This paper describes development and performance of the 611 cc, single cylinder, naturally aspirated, 4-stroke, water cooled dedicated CNG engine with port injection close loop fuel system. The base direct injection diesel engine was re-designed to operate on CNG with advance electronics controls. The engine variables optimised to convert the base diesel engine to operate on CNG were compression ratio, combustion chamber and intake port. Intake manifold was specially designed to integrate CNG injector, TMAP sensor and electronic throttle body. Crank sensor with tone wheel was employed to give TDC and engine speed inputs to the ECU. Lambda sensor was installed on the exhaust manifold for close loop control.This engine with drive by wire technology is not only capable of meeting the stringent BS-IV (4W) emission norms along with IOBD-II compliance but also gives superior performance w.r.t. drivability and startability. The development is already completed and now the engine is ready for the serial production.