Water injection is a technology as old as the steam engine. In fact, that's exactly what a steam engine is- an engine that converts water into steam, and uses the expansion coefficient of steam (1700:1) to drive a piston. Modern racers use water injection in both gasoline and diesel vehicles, not for efficiency but to cool the head (in turbocharged applications where the head is subjected to intense temperatures) and report fuel efficiencies as a result. Generally, the water is mixed with methanol. While water injection has a long history, not much study has been done of the efficiency gained. Most report gains between 10-20 percent.

The Injector

Water is injected directly into the engine air intake, and at a rate which is in direct relationship to the speed of the engine itself. The picture below shows the jet body mounted on top of the intake pipe and the brass jet pointing downwards in the inside of the intake pipe.

The regulator

Any fuel system must include a regulator, that is to say, that the water coming from the tank must be at a constant pressure, otherwise water would pour quickly from a full tank and much more slowly from a nearly empty tank. This is achieved by a "float" system... in this case, by using a 44mm carburetor mounted on a pipe, which both increases the vacuum and improves air flow. Diesel engines don't have carburetors. Mine does. A little confusing!

The tank

I have replaced the small aluminum "scuba" tank you see below with a camelback and a quick disconnect coupling. The water will be in my backpack, and this reduces weight and improves airflow over the original tank you see below.