Water injection systems aren't new to the automotive world, but the idea of using water recovered from an exhaust system is.
Jason Fenske of Engineering Explained dedicated an entire episode to describing how such a system could help create more horsepower and remove water storage tanks from cars that use water injection.
Before we get into that, it helps to understand what water injection systems do. Jason did an entire video on how water injection works in the past, but we'll quickly recap how it works now.
The system sprays water into the intake manifold to create cooler air. The water itself doesn't make horsepower, but the cooler air does. With cooler air, there's less chance for knock, and automakers can dial up boost to make more horsepower secure in the knowledge that water cools the intake charge which makes combustion more efficient.
Knowing that, Jason explains exhaust water recovery systems can take some of the work out of owning a car with water injection because owners won't have to fill their tanks. A water recovery system takes water vapor created as a byproduct of the internal-combustion engine and stores it. Tests performed on a turbocharged, direct-inject 2.0-liter inline-4 engine experimented with different kinds of water separators and where they could be best positioned.
The most logical place was to put the separator after the catalytic converter to catch the water vapor produced after combustion. However, that position also allowed in air that hadn't run through the catalytic converter and was therefore dirty. Engineers also installed a separator after the intercooler before the ambient air enters the engine. Why? It's pretty neat.
That separator collected water vapor from humid air outside of the car. Dense, humid air isn't good for an engine, so the separator stripped the water vapor from the air to make it completely dry before heading to the intake manifold. There, the water the separator collected was injected to cool down the air and make more power. Pretty nifty, we'd say.
How much more power? Jason points out that when running at full load, or 100-percent throttle, the engine's timing could be advanced 20 degrees, it could run a leaner air-to-fuel ratio, and the engine's brake thermal efficiency increased 15 percent from 26 percent to 30 percent. Unfortunately, at that high load, the engine did make more nitrous oxide emissions, but that was to be expected with the engine running so hard. With the engine running at simply a high load, nitrous oxide emissions were lower, which bodes well for everyday driving.
The different types of separators each had drawbacks regarding how clean the water was overall, and how much each collected. Further, when operating at high temperatures (like driving on a racetrack) the system could not collect enough water to sustain itself. However, it did just fine when engine temperatures were kept down, which also shows promise for regular use.
It's all fascinating, so check it out in the video above.