Reducing carbon-dioxide emission (CO 2) is one of the most important challenges of today to overcome. A major source of CO 2-emission comes from the usage of internal combustion engines in vehicles to transport people and goods. This emission is directly proportional to fuel consumption. In order to reduce CO 2-emissions, European Union legislations state that by 2015, the fleet averaged CO 2-emissions from a passenger car manufacturer is limited to 130g/ km. Reaching 2020 the limitations are even tougher, a fleet average of only 95g/km is allowed. If a manufacturer fails to meet these requirements, the manufacturer has to pay "excess emissions premiums" for every car registered, basically a penalty-tax if the requirements are not fulfilled. Fuel consumption is even more important for engines used in heavy trucks. These vehicles travel longer annual distances, making fuel cost a significantly larger part of total costs compared to a passenger car. Hence, improvements in fuel economy are highly desired. Improving engine brake efficiency is vital in order to achieve these requirements. Brake efficiency (η b), is the function of four parts: combustion (η c), thermodynamic (η t), gas-exchange (η ge) and mechanical (η m). All of these efficiencies need to be high in order to reach high brake efficiency. Definitions of these efficiencies are presented in Figure 1. Further information and definitions of the variables used in Figure 1 are presented in appendix A.

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