For some time now, the research area Design has been dealing with systems for the recuperation of engine waste heat in the commercial vehicle sector. Until now, the main focus has been on the layout, simulation and design of expansion engines for use in mobile Clausius-Rankine steam cycles (Fig. 1). In the course of these activities, various reciprocating piston steam expanders were brought up to prototype status, but their function could not be tested in-house due to the lack of an appropriate test facility.

By order of an international motorcycle manufacturer, an engine for driving a motorcycle was developed at the FVT. It is a single-cylinder four-stroke spark ignition engine with a displacement of 150cm³, which is equipped with intake manifold injection, four-valve technology and water cooling. The power transmission is effected via a 6-speed manual transmission, whereby the shifting process should be possible purely manually or semi-automatically, i.e. without manual actuation of the clutch.

The demand for a continuous reduction of fuel consumption in today's automotive drives represents a major challenge for industry. Above all, increasing the efficiency of internal combustion engines is of particular importance, along with efficiency-enhancing measures such as hybridization and alternative drive concepts. A promising approach is the realization of an extended expansion stroke in relation to the compression stroke.

Due to the absence of emissions and the low noise level, the desire for electric mobility is increasing worldwide. However, the short range and high costs prevent the spread and growth of electrically powered vehicles. A promising approach to reducing the disadvantages of purely electric drives is the use of an IC-engine as a range extension. Small-volume spark-ignition engines with 1 to 3 cylinders are usually used for this application.