Water injection from the BMW M4 GTS is coming to the mass market

To keep an engine from blowing up at full power you squirt some water in the cylinder to absorb the heat of combustion. That lowers the temperature, and pressure, and keeps your engine in one piece. It's a trick BMW used on the limited-edition M4 GTS to eke out an extra 49 horsepower from higher boost pressure. And now, the system is coming to more mass-production cars.

According to Autocar, Bosch is offering the water injection system to other automakers and could see production as soon as 2019. The supplier claims water injection can improve power by five percent, and improve fuel economy by as much as 13 percent. We presume this is because an engine can be designed to run either higher compression or higher boost (or both) to eke out more specific output, without risk of long-term reliability issues. Speaking to Autocar, Bosch's Fabiana Piazza said water injection works best on engines that make more than 107 horsepower per liter.

Of course, water injection means carrying water around. Bosch says the system can go around 1800 miles without a refill, depending on the size of the tank. If you run out of water, the engine will simply dial back the peak power. It's not clear how such a system, which requires distilled water, will be adapted to work in cold climates, but Bosch is working on that.