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Two fundamental methods of improving the brake specific fuel consumption of a spark ignition engine at part load have been investigated. These comprise the reduction of pumping losses by variable intake valve timing and changes of clearance volume to increase the expansion ratio. The resulting Otto-Atkinson cycle engine competes with the Diesel cycle engine. Test bed results from a four cylinder engine are reported which largely confirm previous predictions from thermodynamic cycle simulation. The interactive effects between cylinders on pumping loss and mixture requirements are discussed. These results show that brake specific fuel consumption improvements of up to 13% are obtainable from variable valve closure delay alone at some operating points over the usual range of speed and load, and that an additional variable clearance volume control can increase this to a maximum of 20%.

The efficient generation of relatively large quantities of electrical energy in vehicles is becoming an increasingly important issue, as a result of the increasing demands of ancillary electrical equipment and the emergence of hybrid power-train vehicles. An attractive solution to meeting these demands is to extract the electrical energy by means of a generator driven by a high speed exhaust mounted turbine, a technology which is beginning to emerge commercially. This paper is concerned with the design of a system, which extends this concept to enable both electrical generation and highly flexible air management. The heart of the system is a high-speed switched reluctance (SR) electrical machine, the rotor of which is located on a common shaft with the turbine and compressor wheels of a standard commercially available turbocharger.