Video: Bosch develops water injection for gasoline engines

System improves efficiency by 13%

Bosch has developed a water injection system for series production vehicles, and sees the technology as a less complicated way to reduce emissions and improve fuel efficiency while at the same time increasing performance.

The system, which consists of a water injector, railing and water pump, has been in development since 2014 and can provide a 4% reduction in CO2 emissions on the WLTC test cycle and a 13% improvement in fuel efficiency according to the Tier One. At the same time engine performance can be increased by 5% said the firm.

Bosch worked with BMW and first tested the system in the BMW M4 MotoGP Safety Car before using it in the more track-focused BMW M4 GTS, but now the system is ready for wider adoption by OEMs.

Bosch’s project lead for the technology, Martin Frohnmaier, said: “The pump and rail injectors we knew from the gasoline injection business but we had to modify them, especially the pump which is a brand new development because we use demineralised water and this is corrosive and was one of the challenges.”

The water injector is positioned close to the inlet valve and the water spray is directed into the combustion chamber and vaporised during the compression phase.

“We conducted a lot of simulations to find the best spray pattern, with the basic idea to use the water for cooling down the combustion, and with this we can lower the knock tendency leading to a higher thermal efficiency,” Frohnmaier.

Efficiency is improved because the cooling effect provided by water injection reduces temperatures sufficiently to avoid any need to inject additional fuel when operating at or near full throttle.

Bosch is targeting the technology at turbocharged engines with higher than 80kW/litre output, which opens the door to a huge section of the industry. The firm also sees it as a much simpler system to integrate into the vehicle, while also achieving similar results to other, more complex systems.

“We wanted to design an add on system but without huge engine design efforts, and also a system that would be suitable to the end consumer because we are talking about refuelling water. So we did a lot of research with consumers in Germany and the US on how much time they would be willing to refuel the tank, the outcome was between 3,000-6,000km in Germany and 3,000 miles in the US,” said Frohnmaier.

tags: Bosch Powertrain