Efficient powertrains: Less can be more

The most effective way of saving fuel

The intake and exhaust valves on an engine open up to 3,000 times a minute, that’s more than 12 million times over the lifetime of a car. How wide they open is controlled by the shape of the cams on the camshaft: The shaft rotates at half the speed of the engine and determines the valve lift – a technology that has been in use since the 19th century. That may be practical, but it’s not as efficient as it could be. Not all driving situations require the same air/fuel mixture – which influences the intake valves – in the cylinder. There are even situations in which individual cylinders can be deactivated altogether. That reduces fuel consumption by around 15 percent. Again, this technology is not new – it’s been around since the 1990s – but it’s very complex, involving the use of complicated mechanical and electrohydraulic actuators.