Squirts of Water Can Boost Engine Performance, Fuel Economy by 13%

Bosch WaterBoost
Photo: Bosch

According to Bosch, which knows a thing or two about cars, “even advanced gasoline engines waste roughly a fifth of their fuel.” Since everything I know about cars came from trying (and failing) to keep my ancient Swedish turbobrick alive, I’m just going to go ahead and take Bosch’s word for it. Bosch says that in order to keep engines cool, especially when they’re working hard, a bunch of extra gas is used to cool the engine rather than contributing to quickly getting you where you probably should have been 5 minutes ago.

If using gasoline as a coolant seems wasteful to you, that’s because it is, in fact, wasteful. Why not use something else instead? Maybe something that occasionally falls out of the sky for free? Bosch has been working on a water injection system for engines called WaterBoost that can reduce CO2 emissions by 4 percent, boost engine performance by 5 percent, and improve fuel economy by 13 percent.

Essentially, spraying water into the intake cools the entire system. Cooler temperatures during the combustion cycle allow you to pack more air into the combustion chamber, which increases performance. It also results in a more complete burn, reducing pollutants. The fuel efficiency increase comes from the fact that you can get more power out of the same amount of gas, meaning that the engine isn’t sucking down quite as much of it, especially at higher rpms. Consequently, you’ll see the biggest efficiency increase during acceleration and extended highway driving.

The first production car to use this technology was the absurdly expensive BMW M4 GTS, but Bosch is now targeting small, three- and four-cylinder engines with turbochargers. Lots of midsize cars use engines like these, so cumulative benefits should be huge. If you end up owning a car with WaterBoost, you’ll have to remember to fill up a tank with distilled water. However, this isn’t as big of a deal as it probably sounds, because the system uses only a few milliliters per kilometer, meaning that one full tank of water will last 3,000 km or so. And if you forget to fill the tank up for a while, the worst that can happen is that you lose the benefits that WaterBoost offers until you put some water into it again.

As cars ever so slowly transition away from gasoline engines, the fact is that the vast majority of people (which is a lot of people) are going to keep on using them for the foreseeable future. With that in mind, every little bit of improvement in efficiency and reduction in emissions that we can manage is important. And if Bosch can manage to turn something as simple and cheap and refreshing as water into a double-digit boost in fuel economy for the kinds of cars that people actually buy, then yeah, we’re sold.


Cars That Think

IEEE Spectrum’s blog about the sensors, software, and systems that are making cars smarter, more entertaining, and ultimately, autonomous.
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Philip E. Ross
New York City
Willie D. Jones
New York City
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Washington, D.C.
Mark Harris

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