A broad variety of new technologies for improving fuel economy is currently under development or investigation. The general statement is that always a compromise between fuel economy benefit and engine oncost has to be found.
This paper describes a new way for improving fuel economy based on existing technologies used in a refined way.
It is shown that with very simple and robust measures on the intake and exhaust ports and on the valve train mechanism 2 valve and 4 valve engines can show a significant improvement in fuel consumption without having a great cost penalty for production.
The basic system consists of a single cam phaser and a special port arrangement on a 2 valve engine with a single camshaft operated at stoichiometric air/fuel ratio utilizing internal EGR and a reverse “Miller-Cycle”. Variable charge motion is generated using a shared flow through the intake and the exhaust port by varying cam timing. The paper shows that already with this arrangement 2 valve engines can achieve a reduction in vehicle fuel consumption of 5%.
With an add-on of a port deactivation in a 4 valve engine fuel consumption reduction can reach up to 8%.
Further upgrading of the system by adding two step shifted valve lift or super- or turbocharging in order to achieve a further fuel consumption benefit is described.