Electric cars and hydrogen fuel-cell vehicles may get a lot of attention, but every carmaker is still searching for ways to improve the fuel efficiency of internal-combustion engines.

At its Innovation Days 2015 event in Miramas, France, BMW showed off one of several new technologies it's working on to reduce fuel consumption in its future vehicles.

The German carmaker demonstrated a prototype 1 Series hatchback equipped with a water-injection system, which it says can both boost power and increase fuel efficiency.

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Designed for turbocharged engines, the system sprays a fine mist into the intake manifold and cylinders, cooling the pressurized mix of air and fuel before ignition.

This cooling effect can reduce fuel consumption by up to 8 percent, but also increase power by 10 percent, BMW says.

The carmaker also claims that water injection allows its turbocharged engines to use higher compression ratios, but still run on lower-octane gasoline.

BMW 1-Series Hatchback prototype with direct water injection

BMW 1-Series Hatchback prototype with direct water injection

With water injection added, BMW says it was able to increase the compression ratio of the 1 Series' 1.5-liter three-cylinder engine from 9.5:1 to 11.0:1.

The cooling effect also reduces the thermal stress on a number of components, including pistons, valves, turbochargers, and catalytic converters.

Water injection isn't a new concept, but it's rarely talked about for production cars.

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BMW previously demonstrated a water-injection system in its M4 Moto GP safety car, although that application was primarily focused on performance, not fuel economy.

That car's water tank also had to be refilled every time the car was refueled.

In the 1 Series prototype, water is recovered from the air conditioning system--a much more convenient method.

BMW 1-Series Hatchback prototype with direct water injection

BMW 1-Series Hatchback prototype with direct water injection

To guard against freezing, all of the water drains into the tank when the engine is shut off. The tank itself is also positioned in a "frost-protected" location on the car.

BMW did not discuss production plans for water injection, although it's widely rumored that it will be used on the upcoming M4 GTS performance model.

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If the system ever makes it to the U.S., you won't see it on a 1 Series like this prototype, though.

BMW offers the 2 Series coupe and convertible on a similar rear-wheel drive platform here, but not the 1 Series hatchback.

Still, BMW has plenty of other turbocharged models in its U.S. showrooms that could potentially benefit from water injection.


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