Bosch engineers turn to water injection for fuel-saving bonus

Bosch engineers turn to water injection for fuel-saving bonus
Bosch water injection

(Tech Xplore)—A video showing "Bosch water injection" was posted on Wednesday to explain that Bosch has a water injection system featuring something called WaterBoost, for gasoline engines.

The big deal is that it can help support economy. "WaterBoost uses the cooling effect of water to help gasoline direct injection systems place more and cooler intake air into the combustion chamber." This makes combustion particularly efficient, said the presenter, and "delivers an extra kick when accelerating."

Bosch has introduced its water injection system as a way to cool the engine and generate an additional boost. Especially at high engine speeds, some of the gasoline is used for cooling instead of for propulsion.

Autocar put it this way: "The system works by spraying a fine vapour of distilled water into an engine's intake before fuel combustion, reducing engine temperatures and therefore decreasing knocking, which wastes fuel."

Bosch discussed their principle in more details with a Wednesday announcement:

"The basis of this innovative engine technology is a simple fact: an engine must not be allowed to overheat. To stop this from happening, additional fuel is injected into nearly every gasoline engine on today's roads. This fuel evaporates, cooling critical components like the block and turbo charger. With water injection, Bosch engineers have exploited this physical principle. Before the fuel ignites, a fine mist of water is injected into the intake duct. Water's high heat of vaporization means that it provides effective cooling."

The BMW M4 GTS, said the company, is the first production vehicle "to feature an innovative and groundbreaking water injection system."

Sam Sheehan, Autocar, reported that the water injection system from the BMW M4 GTS will feature in more car models from 2019. Bosch's Martin Frohnmaier, in Autocar, said "We can say that we expect the system to make mass production from 2019."

(Sheehan said that BMW's position as co-developer of the system makes it a likely first candidate to introduce water injection into more of its models.)

Bosch said the fuel economy offered by this technology comes especially to the fore in three- and four-cylinder downsized engines, the kind of engines found under the hood of any average midsize car.

Bosch engineers turn to water injection for fuel-saving bonus
Bosch water injection

Speaking to Autocar, Bosch global project manager Fabiana Piazza said they were launching it now "as tighter legislation and new real driving emissions tests are increasing the importance of this technology in all cars."

Should you ever end up with a car using WaterBoost, Evan Ackerman in IEEE Spectrum said, "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."

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User comments

Sep 02, 2016
By 2019 batteries will certainly be cheaper than internal combustion engines. Why bother?

Sep 02, 2016
Exactly, cps.

Just get an electric vehicle and have superb acceleration, clean quiet operation, and huge savings in operational costs.

Sep 02, 2016
"By 2019 batteries will certainly be cheaper than internal combustion engines. Why bother?"

You wish. The price would have to drop more than tenfold in two years for that to be true.

Sep 02, 2016
As far as water injection goes, it's actually a very old invention. It was used as far back as 1962 in cars.


The point isn't really about cooling the engine, because the amount of fluid injected is entirely too small to carry away a significant amount of heat. The main point is to cool the fuel charge to increase its density - the same effect as using an intercooler - and to prevent detonation under high compression when the engine is running at open throttle.

Injecting excess fuel under WOT conditions both cools the fuel charge to fit more of it in the cylinder, and prevents detonation or knocking by making the mixture harder to ignite, but it wastes fuel and produces more pollution, so it makes sense to use water instead of fuel to perform the same duty.

To put it in simple terms, water injection allows you to run higher turbo boost pressures without breaking the engine.

Sep 02, 2016
Of course, if you forget to fill the water reservoir, the ECU will kick back the boost pressure and the engine simply loses power.

Sep 02, 2016
Back in the 50's and 60's there was a popular conspiracy theory that you could run your car with just water but the oil companies stole and hid that technology. :P

Sep 03, 2016
None of that complicated mechanical stuff in an EV, which has much lower operational costs, as well.

Sep 03, 2016
Eikka, it goes back even further than that. Water injection was used in aircraft engines during WW II to improve detonation margins with the often poorer quality fuel they had to use.

In cars, advancing the timing can help extract more power, but it increases the likelihood of detonation. As the article points out, water injection can help.

The problem is something that even blowhards such as Rush Limbaugh have noticed: Distilled water is significantly more expensive than gasoline. If you're seeking performance with possible environmental benefits, water injection may interest you. But it is still more expensive, and earlier tests discovered that pollutant reduction may not be as good as hoped. Maybe Bosch has addressed that problem with more precise injectors.

Sep 04, 2016
Then there's the problem of winter...

Sep 07, 2016
Water injection goes back to before WWI possibly even back to the 1890,s

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