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For engines with rather fast changing load-cycles a simple system is proposed to cool the combustion air in the upper load-range and heat it in the lower range. This “levelling system” is self contained and works without any connection to the ambient air or to the cooling circuit of the engine. It relies basically on means, which enhance the thermal inertia of the inlet manifold in combination with an efficient heat exchange with the combustion air. Examples are given for different applications. Test results prove the advantages of the system and are compared with results of ordinary aftercooling systems. Furthermore it is shown that even aftercooled engines may benefit from a higher thermal inertia. The paper demonstrates that a levelling system is an economical and usefull means to improve the behaviour of ail types of supercharged engines.

A rough estimate of the energy components in internal combustion engines for motor vehicles indicates that the total fuel energy is converted to one-third each into mechanical energy, engine coolant heat and exhaust energy. This large share of waste heat in the exhaust motivates various attempts to recover the remaining exergy in the exhaust. Intensifying charge air cooling by an exhaust-heat-driven cooling system provides a promising approach to engine waste heat recovery. The exhaust energy is most suitable for this recovery effort due to its higher temperature level in comparison to engine coolant. A further decreasing of charge air temperature provides an additional degree of freedom, which expands the boundaries concerning engine application.