Water Injection helps several ways.
1. Water enhances fossil-fuel combustion, particularly when used with Brown’s Gas (aka BG or HHO).
2. Water cleans the combustion area and valves in several ways; first by flash cooling red hot carbon deposits, causing them to flake off (this also tends to reduce pre-ignition and or detonation problems), second by helping the carbon burn (both the carbon buildup and the incoming fuel), third by reducing the volume of fuel needed to produce the same amount of power (less fuel means less potential carbon buildup).
3. Done correctly, water can replace the need to add ‘quenching/cooling’ fuel to keep exhaust temperatures down. As explained in my Double Mileage Guaranteed eBook, only about 10% of the fuel that goes into an engine (with ‘vested interest’ OEM fuel systems) actually powers the engine. It’s totally practical (using water to replace excess fuel) to reduce the actual liquid fuel by 50% (or more) while maintaining full power output. As a bonus, the pollution levels are reduced to almost nothing.
4. Water Injection reduces the amount of water the engine has to handle. Even most mechanics don’t know this because they aren’t taught organic chemistry. A gallon of gasoline turns into nine (9) gallons of water when combusted. If 50% of the fuel is replaced with water, then there is only four and a half (4.5) gallons of water produced by combustion of the fuel. The net result is that the engine only has to handle five (5) gallons of water (4.5 from fuel and 0.5 from water injection).
5. As explained above, water injection tends to reduce engine knock (aka pre-ignition or detonation). This is a well established fact and used to help increase horsepower by being able to further advance ignition timing.
Water does NOT rust the engine or exhaust system, as explained above, water injection actually reduces the water the engine is already handling.
Water does NOT increase engine wear. Oil and water do not mix, so water does not wash lubricating oil off the cylinder walls. Liquid fuel washes oil off the cylinder walls (ask any mechanic that uses fuel to wash oil off parts when cleaning them), so adding water and reducing liquid fuel actually reduces engine wear.