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The mechanical fully variable valve lift system UniValve represents one of the new technical solutions for a throttle free load control for combustion engines. The load control is achieved by the variation of the valve lift and the simultaneous variation of the opening and closing time. The design of the system has as result a simple layout with a valve train component assembly that leads to a compact integration into conventional cylinder heads. In addition to the first results presented at the SAE Congress 2004 this paper provides the results of the fired engine and the valve train operation on the component test bench. Furthermore the potentials of the throttle free load control with the UniValve system in comparison to a conventional throttle engine operation with the same engine type are pointed out. Perspectives for the application in an four cylinder engine are given.

Today, downsizing through active displacement control is in series production using cylinder deactivation (CDA) concepts. However, current systems deactivating two cylinders of a four-cylinder engine are limited regarding the effective CO2 saving potential due to the confined usable operating range of the two-cylinder mode. Therefore, the objective of the current investigation is a three-cylinder engine with the possibility to activate an additional (fourth) cylinder. For this purpose, a four-cylinder series engine was modified to the firing order of a three-cylinder engine for the first three cylinders. The exterior cylinders 1 and 4 are operated in parallel, with the fourth cylinder deactivated in efficiency mode. Launching and idle mode are also operated with three active cylinders. Additional modifications to the valve train were carried out in order to further exploit the increased residual gas tolerance due to the load point shift.