The injection of water into engine cylinders produces a cooling effect that boosts power and torque, particularly when operating at or near full throttle, while at the same time reducing fuel consumption and emissions.

BMW has already implemented a water injection system in its BMW M4 MotoGP Safety Car, and, at the recent BMW Group Innovation Days 2015 event, presented the technology in a prototype of a model from the BMW core brand powered by a latest-generation three-cylinder gasoline engine. (Earlier post.)

The water injection system in the BMW M4 MotoGP Safety Car draws water from a five-liter tank in the trunk. Under grueling race conditions, when the vehicle spends a lot of time operating at full throttle, the water tank is topped up every time the vehicle is refueled.

Bosch also is developing a water injection (WI) system for spark ignition engines in partnership with a pilot customer, said Dr. Rolf Bulander, member of the board of management of Robert Bosch GmbH and chairman of the Mobility Solutions business sector, in his talk on powertrain optimization at the 2015 Vienna Motor Symposium. (Earlier post.)

FEV’s system concept offers potential synergies which can be further enabled by exhaust heat recovery. There is also a possible extension of this concept, in which the condensed water from the air conditioning system can be added to a buffer tank from which the condensate is extracted and fed into the engine.

FEV began in 2014 with initial investigations on a turbocharged gasoline direct injection (GDI) engine that featured PFI injection of the EGR condensate. Subsequently, the engineers extended the concept to include direct injection of the condensate into the cylinder. They changed the condensation concept to allow utilization of the condensate from the entire exhaust gas stream and not only EGR condensate. This operation principle allows the entire injected condensate to be recycled.

In an engine with a compression ratio of 13.5:1, studies of condensate injection in combination with the Miller cycle and cooled external EGR was evaluated at IMEP = 14.5 bar at n = 2,000 rpm. Despite the high compression ratio, knock was limited.

Influence of the injected water quantity on stoichiometric combustion with cooled EGR at n = 2,000 rpm and IMEP = 14.5 bar. Source: FEV Spectrum. Click to enlarge.

Resources

• Fabian Hoppe, Matthias Thewes, Henning Baumgarten, Jürgen Dohmen (2015) “Water injection for gasoline engines: Potentials, challenges, and solutions” International Journal of Engine Research doi: 10.1177/1468087415599867

• FEV Spectrum: “Gasoline Combustion Beyond 2020”

• Matthias Thewes, Fabian Hoppe, Henning Baumgarten, Jörg Seibel (2015) “Water Injection for Gasoline Combustion Systems” MTZ worldwide Volume 76, Issue 2, pp 10-15 doi: 10.1007/s38313-014-1012-0