SmILE

SmILE is a showcase car designed for Greenpeace in 1996 to demonstrate how fuel efficient a car can be. The name stands for "Small, Intelligent, Light, Efficient'. It is based on the Renault Twingo, halving its fuel consumption to 3.3 l/100km (30 km/L or 85 mpg (imperial) / 68 mpg (US)). An important issue in the design was that it should use off-the-shelf technology (parts and know-how). As a result, in mass production it should not cost significantly more than a 'heavier' equivalent. The engine should even be cheaper because it is made of fewer parts. However, parts that would be more expensive are supercharging (be it pressure wave supercharger or turbo-supercharger) and the wheels and the wheel suspension, which are made of aluminium. The major changes made to the Twingo are: 23% lighter (650 kg instead of 845 kg): 80 kg less because of a smaller engine and lighter peripherals (battery, radiator and exhaust system) 80 kg less in vehicle interior and chassis through lighter seat structures (aluminium / plastic) and lighter metals for wheel suspensions, drum brakes, brake calliper and rims. To keep the cost down, no exotic materials (such as titanium screws or carbon gear boxes) were used. lighter wheels, which also have a rolling resistance that is 35% lower. Less air resistance, with a 30% improvement in the wind tunnel (Cw value (drag coefficient) down from 0.37 to 0.25) A smaller and more efficient engine: a supercharged flat-twin, four-stroke engine with four-valve technology in a boxer arrangement. A maximum torque of 75 N·m results from a swept volume of 358 cm3 at 2,900 rpm. The dynamic pressure supercharger makes sure the engine runs most efficiently at normal operating speeds. Most car engines are designed for optimum performance at maximum speed and load, which are in reality rarely used. At 55 bhp, the engine has the same performance as the original Twingo. Other performance parameters, such as maximum speed, elasticity and acceleration are the same or better. The main consumption change of the engine stems from its more frequent use in the higher load range, which results in higher thermal stress. This is compensated for by an ingenious cooling system. The mean piston velocities are in the customary range. The use of the latest technologies in materials and surface coatings guarantees stability of piston rings and cylinder bearing surfaces despite the higher pressures due to supercharging.