BMW testing new injection tech for future M cars

By Bob Nagy on February 16, 2015 8:15 AM

Set to serve as the official safety car for the FIM's World Championship MotoGP Series, the BMW M4 will be used to evaluate performance-enhancing water-injection that "will be employed in a BMW M production model in the near future" following completion of track testing. While this technology has been used to enhance performance of internal combustion aircraft engines as well as in several aftermarket automotive applications, BMW is set to become the first manufacturer to commit to water injection as an element of its factory performance  M Division.

More power, better economy 

Water injection can be used to achieve several seemingly contradictory goals by increasing output of a given displacement engine, reducing emissions and enhancing fuel economy. It's particularly effective in supercharged/turbocharged engines operating at the limit. A fine water mist is sprayed into the intake plenum and evaporates before actually entering the combustion chamber, which along with an intercooler, lowers the temperature of the highly compressed intake air from the turbo. This, in turn, helps reduce heat-generated detonation - commonly referred to as "knock" - and allows for the ignition timing to be advanced and boost levels increased under full-throttle operation. Not only does this translate into more power, but it can improve fuel economy by up to 8-percent compared to a comparable "dry" configuration. The lower exhaust temps also help reduce nitrous oxide (NOx) emissions. BMW notes that while ultimate performance is the main goal, the system can be adapted to bias more of its benefits towards additional mileage gains for certain  street applications. 

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In addition to the water injectors - in the case of BMW's 3.0-liter Inline-6 engine a trio of plenum-mounted nozzles, one for each pair of cylinders - the package includes a water reservoir that holds about 1.3 gallons of water mounted in the trunk along with the pump, sensors and actuators. In full race trim, the water tank needs to be replenished with each refueling stop, but on a street car running under "normal" conditions, BMW says that interval could be upped by a factor of five. The system also incorporates built-in diagnostics to warn if the reservoir is running dry and automatically compensate to ensure no damage is done to the engine. 

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BMW says the M4 Safety Car "offers a clear perspective of an M car that will set a new benchmark in terms of performance, exclusivity and individuality... with benefits both on the racetrack and in everyday use." It's possible we could see the first street application of water injection on an M car this September at the Frankfurt Auto Show.

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