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Two-stroke engine gas exchange simulation requires several significant code modifications in comparison to standard four-stroke application. This paper describes the present work based on the PROMO code. Important features currently modelled are a scavenging model, a crank case model and a reed valve model. First results based on calculations for a crank case scavenged engine show the present state of the code and the influence of some design parameters on the engine performance.

The NVH optimization is a key issue for the development of future powertrains. This includes the radiated noise in terms of noise level and sound quality as well as the structure-borne noise excitation via the engine mounts. Experience shows that there are generally no single noise relevant components on modern powertrains which dominate the NVH behaviour. In contrast, a good NVH performance can only be achieved if the optimization process includes every single component and excitation. Only the combination of these optimized designs can lead to a first-class powertrain NVH. Within this paper the NVH optimization process of an existing 4-cylinder in-line spark-ignition powertrain is described. Examples for positive NVH designs are presented and their effect on the NVH behaviour are explained. Combining all positive NVH features into the engine resulted in a noise reduction of 3-5 dBA without any negative effect on fuel economy and performance.

The study presented in this paper is concerned with the application of a finite element based technique to deal with crankshaft-crankcase interaction. A finite element model of the crankshaft and the crankcase was developed and appropriately reduced. This model was used for a crankshaft optimization, strategy to analyse related effects on the NVH performance with focus on main bearing acceleration. The crankshaft and the cylinder block were modelled using beam and shell elements with structural and dynamic properties correlated up to 1600 Hz. The interaction between crankshaft and the cylinder block was represented by using non-linear properties. Applying this model, the dynamic crankshaft and engine block behaviour and repercussion on NVH performance was analysed by investigating main bearing acceleration.