Turbocharging Small Displacement Spark Ignition Engines for Improved Fuel Economy

This paper describes an approach to improve the fuel economy of given cars with the aid of turbocharged SI engines of relatively small displacement, 1.6-l 4-cylinder and 2.2-l 5-cylinder configurations, to replace bigger, NA engines of the same power potential.

This approach uses an engine turbocharger system which consists of a low-flow turbocharger in order to realize a given peak performance goal with good power characteristics over the entire engine-speed range. The boost pressure is controlled by a wastegate. The air/fuel mixture is prepared by a two-stage carburetor at the intake side of the TC compressor. The oxygen concentration in the exhaust gas is measured by an oxygen sensor upstream from a three-way catalyst.