Bosch more broadly commercializing water injection system; up to 13% fuel savings under some conditions
Bosch is now more broadly commercializing its water injection system for turbocharged engines (earlier post). Bosch currently supplies water injection parts for the BMW M4 GTS—the first production vehicle to feature a water injection system. (Earlier post.) In the vehicle’s turbocharged six-cylinder engine, it offers improved performance and consumption even at full load.
Bosch’s WI system comprises a water pump; a water rail; and injectors which have been designed to handle the specific challenges arising as a result of operation with water. Particularly when accelerating quickly or driving on the freeway, the injection of additional water makes it possible to reduce fuel consumption by as much as 13% in highway conditions and 4% in normal driving (WLTC).
In a presentation in 2015 at the Vienna Motor Symposium on Bosch’s WI work, Dr. Rolf Bulander, chairman of the Bosch Mobility Solutions business sector and member of the board of management of Robert Bosch GmbH, explained that the improvement in fuel consumption results from cooling the charge to minimize/avoid fuel enrichment; mitigating knocking (premature denotation); and enabling an increased compression ratio. A port-injection WI system is low complexity and highly effective, he noted.
With our water injection, we show that the combustion engine still has some tricks up its sleeve.—Dr. Rolf Bulander
The fuel economy offered by this Bosch technology comes especially to the fore in three- and four-cylinder downsized engines—precisely the kind of engines to be found under the hood of any average midsize car.
Water injection can also boost power by up to 5%, Bosch says. Earlier ignition angles mean that the engine is operated even more efficiently. On this basis, engineers can coax additional power out of the engine, even in powerful sports cars.
Only a small additional volume of water is needed: for every one hundred kilometers driven, only a few hundred milliliters are necessary. As a result, the compact water tank that supplies the injection system with distilled water only has to be refilled every few thousand kilometers at the most.
If the tank should run empty, the engine will still run smoothly—albeit without the higher torque and lower consumption provided by water injection. The water flows back into its tank when the engine is stopped, where it may freeze in cold weather. The water is thawed following the re-start of the engine.