| 摘要 |
The invention relates to a method for actuating intake valves and exhaust valves of a four-stroke direct-injection gasoline engine. At low torque, a parallel retardation of the intake valves and exhaust valves is carried out, so that, at the commencement of the intake stroke, the exhaust valve is still open and the intake valve is still closed after top dead center (TDC) of the piston. High internal exhaust gas recirculation (EGR) occurs, irrespective of the pressure in the intake manifold. The resulting internal EGR is sufficient to displace the 50% MFB timing to its optimal position after TDC and to reduce nitrogen oxide emissions.
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