INCREASING FUEL EFFICIENCY OF CARS

The driving resistance produced by body shape for a given vehicle surface area is influenced decisively by the resistance coefficient. With a resistance coefficient of 0.3 and an average class weight of 900 kg - which is considered to be attainable - these measures alone produce an improvement in economy of about 20%. - improvements to propulsion are possible firstly by increasing the thermal and mechanical efficiency of the engine and secondly by more frequent utilization of the engine's best consumption points in the driving cycle. Electronic control and regulating equipment will come into use in the future as fundamentally new aids to such improvements. Amongst diesel engines improved economy is to be expected when turbo-supercharged diesel engines can be entered into mass production. More economical driving is also provided by 5-speed gearboxes and particularly where the fifth gear is used as an overdrive. A further advance would be, for example, the introduction of free-wheeling. - it is calculated that a vehicle with A test weight of 1000 kg could have an optimum consumption with a diesel engine of 33.5 km/l in the mixed us-cycle. - finally it is noted that the current conflicting legislation impedes the development of optimum-consumption cars. (TRRL)