Engine downsizing

Engine downsizing is the use of a smaller engine in a vehicle that provides the power of a larger engine, through the use of recent technologies. It is the result of car manufacturers attempting to provide more efficient vehicles that emit less emissions, often given in by legalization. The term generally relates to traditional internal combustion engines powered by petrol or diesel.

Many manufacturers are reducing engine capacity and number of cylinders. By adding a boosting device (turbocharger or supercharger) and direct injection technology, they provide a powerful engine with similar performance to a much larger engine, but with much improved efficiency and reduced carbon emissions. A smaller engine is also often lighter, so the car can be lighter and therefore nimbler. Reducing the number of cylinders also reduces the amount of friction in the engine, increasing the efficiency.

Some observers have not been convinced by manufacturer's claims that reducing engine size provides a more efficient car. Tests have shown that some downsize engines have lower fuel economy in everyday driving than the larger engines they replace.

The University of Bath published research carried out by its Powertrain and Vehicle Research Centre which demonstrated that it is possible to reduce engine capacity by 60% and still achieve the torque curve of a modern, large-capacity naturally-aspirated engine, while encompassing the attributes necessary to employ such a concept in premium vehicles.

In an Auto Bild investigation of an 1.0 EcoBoost Ford Focus having driven 100,000 kilometres (62,000 mi), no major issues were found surrounding the engine, with only 'minimal oil sweating between cylinder and block' being noticed. However, the turbocharged Audi 2.0 TFSI petrol engine has frequently been reported to suffer from more severe oil leakage around the cylinder seals, with up to 1 liter of oil consumed per 300 kilometres (190 mi). Similar issues have been reported for Volkswagen Group 1.4 and 1.8 TFSI engines. According to a J.D. Power survey, downsize engines scored significantly lower in reliability than older engines.

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