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The main focus nowadays for the development of future vehicle powertrain systems is the improvement in fuel efficiency alongside the reduction of pollutant emissions and greenhouse gasses, most notably carbon dioxide. The automotive community is already engaged in seeking solutions to these issues, however, the ideal solution, namely zero emission vehicle is still regarded as being a long way from fruition for the mass market. In the meantime steps are being taken, in terms of engineering development, towards improved fuel efficiency and sustainability of relatively conventionally powered vehicles. One approach to the decarbonization of road vehicles is to supplement existing fossil fuels with sustainable biofuels.

A holistic modelling approach has been employed to predict combustion, cyclic variability and knock propensity of a turbocharged downsized SI engine fuelled with gasoline. A quasi-dimensional, thermodynamic combustion modelling approach has been coupled with chemical kinetics modelling of autoignition using reduced mechanisms for realistic gasoline surrogates. The quasi-dimensional approach allows a fast and appreciably accurate prediction of the effects of operating conditions on the burn-rate and makes it possible to evaluate engine performance. It has also provided an insight into the nature of the turbulent flame as the boost pressure and speed is varied. In order to assess the sensitivity of the end-gas chemical kinetics to cyclic variability, the in-cylinder turbulence and charge composition were perturbed according to a Gaussian distribution.

This paper describes the initial development of a 3 cylinder 1.2l technology demonstrator engine from MAHLE. The purpose of this highly turbocharged direct injection engine is to demonstrate production-ready technologies that enable low CO2 emissions via downsizing by 50%. Downsizing is one of the most proven paths to CO2 emission reduction. By using careful design, a 2.4 l engine can be replaced by a 1.2l engine that has superior torque at all speeds and on-road fuel consumption benefits of 25 - 30%. A two-stage turbocharging system has been developed for the engine to enable good transient response and the high torque levels at all engine speeds demanded by a downsizing approach. Several options were tested and the final system exceeds the 30bar peak BMEP target with stoichiometric fuelling. Indeed, lambda = 1.0 fuelling is maintained over the majority of the full-load line and the 144kW peak power requirement is fulfilled at only 6000 rpm.