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In the port injected Spark Ignition (SI) engine, the single greatest part load efficiency reducing factor are energy losses over the throttle valve. The need for this throttle valve arises from the fact that engine power is controlled by the amount of air in the cylinders, since combustion occurs stoichiometrically in this type of engine. In WEDACS (Waste Energy Driven Air Conditioning System), a technology patented by the Eindhoven University of Technology, the throttle valve is replaced by a turbine-generator combination. The turbine is used to control engine power. Throttling losses are recovered by the turbine and converted to electrical energy. Additionally, when air expands in the turbine, its temperature decreases and it can be used to cool air conditioning fluid. As a result, load of the alternator and air conditioning compressor on the engine is decreased or even eliminated, which increases overall engine efficiency.

Two of the most pressing challenges of the automotive sector are reduction of fuel consumption and corresponding emission of greenhouse gases, especially when taking into account the growing degree of luxury in modern passenger cars, which increases the auxiliary load on the engine. Preferably, this increase in auxiliary load is compensated by the recovery of waste energy. To accomplish this, a technology called WEDACS (Waste Energy Driven Air Conditioning System) is being developed to recover throttling losses. WEDACS uses a turbine to induce provide the engine with the same air mass flow rate as a throttle valve while producing mechanical energy and cold air. An alternator coupled to this turbine converts mechanical energy into electrical energy and the cold air is used to cool A/C fluid. This way the load of both the engine mounted alternator and A/C compressor is reduced or eliminated, resulting in higher efficiency.