The Miller cycle, using an early inlet valve closing, can significantly improve the overall efficiency of a spark ignition engine during partial load operations. The shorter valve intake event minimizes the need for throttling the air and so reduces the pumping losses. This method is known as “dethrottling”. Indeed, the use of a variable valve lift system makes it possible to combine two different cam profiles in an engine, one for the full load operations and one for the partial loads. The benefits of this strategy, combined with a variable valve timing (VVT) system, will be explored using a new 0D model. This model can take into account the strong changes of in-cylinder turbulence generated by the VVT and their effects on the combustion. Efforts have been made to reduce the model's reliance on external inputs. Therefore, analytical calculations of quantities, such as the flame radius, have been favored. The Miller cycle can lead to indicated efficiencies around 44% and the addition of a VVT system can improve the overall efficiency up to 1% over a wide range of engine loads.

米勒循环使用提前关闭进气门，可以显着提高部分负荷运行期间火花点火发动机的整体效率。较短的阀门进气事件最大限度地减少了对空气节流的需求，从而减少了泵送损失。这种方法被称为“去节流”。实际上，可变气门升程系统的使用使得在发动机中组合两种不同的凸轮轮廓成为可能，一种用于全负载操作，一种用于部分负载。将使用新的 0D 模型探索这种策略与可变气门正时 (VVT) 系统相结合的优势。该模型可以考虑 VVT 产生的缸内湍流的强烈变化及其对燃烧的影响。已努力减少模型对外部输入的依赖。所以，诸如火焰半径之类的量的分析计算受到青睐。米勒循环可实现约 44% 的指示效率，而添加 VVT 系统可在广泛的发动机负载范围内将整体效率提高 1%。