Investigation of a Cylinder Activation Concept for a Turbocharged Direct-Injection Gasoline Engine

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. The increased ignition intervals, in conjunction with a very late intake closing timing (Atkinson cycle), improve the boundary conditions with respect to knocking tendency and lead to fuel saving potential even in the higher load range. This extends the map range of the efficiency mode up to full load in three-cylinder operation and therefore doubles the usable range compared to a conventional deactivation concept. The fourth cylinder is activated only when the maximum nominal power is required. In this operating mode, the load of the fourth cylinder can be continuously increased by the use of a fully variable valve train as an activation element. This activation strategy was simulated with a detailed 1d-simulation model. Based on the measurement data, simulation models of the original and the modified engine with a calibrated predictive combustion model have been set up. Using this simulation environment, both concepts were compared in a “virtual test drive” under the same boundary conditions.