Water injection they key to suppressing detonation and gaining power and mileage

[d_m_kolb]

Water injection decreases the possibility of detonation by lowering the combustion chamber temperatures and increasing the effective "octane" of the fuel. This allows the engine to run a higher boost and full spark advance without the use of race gas. Additionally, if the water is atomized in the intake stream, there is an additional cooling of the intake charge. Both effects are increased with the inclusion of 50% alcohol to the mix (don't spray the exterior of an intercooler with alcohol!, this refers to internal injection only). The additional fuel of the high octane alcohol will in turn allow boost beyond what the factory fuel system can deliver. Water injection also has the effect of "steam cleaning" the combustion chambers and exhaust valves. This removes the carbon build up that decreases efficiency and leads to pre-ignition(detonation). It will also keep the throttle body and interior of the intake manifold much cleaner than normal.These systems are great for the turbo or supercharged engine but also work on a normally aspirated engines as well. I have a home made set up on my vehicle and can run the cheap fuel now with no knocking and my gas mileage has increased alittle.Here is a link to a home made set up. http://www.dawesdevices.com/water.html This is a link to a manufacturer that makes a complete kit. http://www.racetep.com/wik.html Normally Aspirated Water Injection System Turbo Water Injection System

[Sub-Zero]

this is pretty old school like putting in a quart of ATF into the engine oil to clean things up right before an oil change i wonder if my car's brief stint with water (got sucked up the intake pipe) had any 'positive' effects

[jeremyk]

Yes, this is very old school, but extremely effective in engines that used forced induction. Water injection was first used in airplanes (many had superchargers) back in WWII.I built my own water/alcohol injection system for my Stealth. Cost me less than $150 and it works great. This system allows me to run 3lbs more boost on pump gas than I would normally be able to run. That translates to about 50hp (500hp total at 18psi). I only run at 15 most of the time because 500hp just isn't necessary for my 10 mile commute to work. This was also marketed as a gas mileage improver back in the '70's but I think the principles for improving gas mileage are a little different than they are for increasing power in a turbo/supercharged engine.There would be very little benefit to adding somethink like this to a normally aspirated computer controlled car running on decent gas.
[Modified by jeremyk, 6:13 PM 8/30/2002]

[d_m_kolb]

Actually you'd be surprised. Even on a naturally aspirated car that requires high octane gas with a water injection system you could get away with running the cheap stuff with no knocking. Plus it would help HP from the water vapor slightly filling the cylinder when it heats up causing more pressure in the cylinder. I have done my own tests with water injection and on a none forced induction engine it will improve performance slightly and also help gas mileage.