What is water injection and what does it do for the car. How much does it cost to add.

Water injection was first used in a car at Daytona in 1911 (I might be off by a year or two). It can have several benefits in a car. The water vapor will prevent carbon buildup (and actually remove old deposits), it can increase intake charge density, allowing more power and greater efficiency, and it can have a cooling effect on a Supercharger. Water injection was also used in WWII for our fighters and bombers. This is one of the reasons we had higher service ceilings than the Axis powers. We could 'create' higher air density to keep the Supercharged aircraft engines from starving at high altitudes.

Common applications are usually limited to SC or Turbo equipped cars. Unless you have one, your gains would be minimal, and the good systems are quite expensive. You need a variable flow (ideally), so that it delivers proportional amounts at different RPM'*.

It'* really not an everyday driver type of mod. Not something that you'd run all the time, and there is a slight risk of hydrolock.

hmm... you sparked me. could water injection be used in moderate amounts to say... clean out a 93 se with too many miles driven by a retard?

You can accomplish the same thing with a clean spray bottle. Spray it into the intake while the car is running....in bursts that almost kill the idle. Or rev it and spray more at a time.

It'* best to disconnect the downpipe first. You may dislodge chunks that you don't want in your Cat. A fogger system of water injection won't dislodge huge chunks like that. Little bits at a time that will pass through the cat and muffler.

In the long run, it'* probably best to set this up BEFORE finishing your exhuast