Water and fuel aren't usually a good mix, but BMW has turned to water injection technology in its ever-continuing quest for improved fuel economy and power. Its latest 1 Series prototype is fitted with such a system to help create lower combustion temperatures, which brings fuel economy benefits of up to 8 percent on the road.

Central to the benefit of water cooling is its ability to cut down on combustion temperatures. With lower combustion temperatures comes improved economy and a reduced risk of "knock", which allows BMW to run a compression ratio of 11:1 instead of the lower 9.5:1 it usually uses in its three cylinder engine. This higher compression ratio brings about better fuel efficiency on low and medium throttle applications, contributing to the improved economy offered by a water-cooled engine.

BMW's system draws water from a small tank and sprays a fine mist into the intake manifold plenum where it evaporates, reducing combustion temperatures by around 25° C (45° F).

As well as offering instant economy and performance benefits, the lower temperatures that water cooling creates reduces the strain on everything from the engine's pistons and valves to its catalytic converter and turbocharger, potentially improving the longevity of those components.

Thanks to the earlier ignition point and the increased boost it allows, the water cooling system in the 1 Series frees up 10 percent more torque and power than offered in the standard car.

The new 1 Series tester isn't the first time BMW has fitted one of its cars with a water injection system. The BMW M4 MotoGP safety car is fitted with a similar system. Whereas the MotoGP M4 draws its water from a manually filled tank in the boot, however, BMW's latest water-cooled prototype is fitted with a water recovery system that constantly tops itself up with condensed water from the air conditioning system.

As is the case with the M4's system, the 1 Series drains all of the water from the system's hoses back to the freeze proof tank when the car is turned off to ensure it doesn't freeze up or cause corrosion.

BMW has not announced a timeline for full-scale production, but when the MotoGP M4 car was launched the brand said "following intense testing within the MotoGP World Championship, the water injection system will also be employed in a BMW M production model in the near future."

Source: BMW

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