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This contribution is focused on an investigation of two well-known techniques, i.e. the modified Atkinson working cycle with a late intake valve closing (LIVC) and the Miller working cycle with an extreme early intake valve closing (EIVC) in order to increase the fuel economy of a throttled SI engine at a part load (high throttled mode). However, the application of the Atkinson and Miller cycle causes a decrease in the in-cylinder charge temperature before the compression stroke. In the case of a constant value of the geometric compression ratio, the in-cylinder charge temperature at the beginning of the combustion is also decreased and the combustion is then slower (compared to a standard Otto cycle). This could negatively influence the indicated efficiency of the unconventional cycle. In order to avoid this, increase in the in-cylinder charge temperature was provided due to mixture heating in the intake manifold of the engine.

The focus of this paper is the adaptation of an existing direct current (DC) dynamometer to transient operation in order to facilitate at least preliminary transient tests carried on for low-budget engine development purposes. The original control software does not allow any dynamic testing. Therefore, new software for the test bench control was developed for the purposes of transient cycles testing. The software was applied on the test bench equipped with a DC dynamometer. The software is able to control the dynamometer, acceleration pedal and other additional functions like read and control ECU calibration software INCA, communicate with an acquisition system and other.