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CNG has recently seen increased penetration within the automotive industry. Due to recent sanctions on diesel fuelled vehicles, manufactures have again shifted their attention to natural gas as a suitable alternative. Turbocharging of SI engines has seen widespread application due to its benefit in terms of engine downsizing and increasing engine performance [1]. This paper discusses the methodology involved in development of a multi cylinder turbocharged natural gas engine from an existing diesel engine. Various parameters such as valve timing, intake volume, runner length, etc. were studied using 1D simulation tool GT power and based on their results an optimized configuration was selected and a proto engine was built. Electronic throttle body was used to give better transient performance and emission control. Turbocharger selection and its location plays a critical role.

Vehicles with direct injection engines employ various methods for mixing fuel and air in an engine cylinder. Efficient mixing increases combustion burn rate, improving combustion stability and knock suppression. Spark ignition engines may use tumble flow motion to generate turbulence, which includes rotational motion generally perpendicular to the cylinder axis to improve air and fuel mixing. Depending on operating conditions, more or less tumble may be advantageous. In this paper the tumble motion of the charge air is studied and simulated only in the suction stroke. A direct injected turbocharged combustion system employing central-mounted multihole injector. This paper presents the comparative study of effect of intake port design with various levels of tumble motion for fuels used in SIDI engines on the engine performance characteristics.