Has anyone tried this with a rotary engine yet? Trying to think of any really bad things(tm) it would do.

 

Unless you're running alot of boost don't bother.

 

Out of curiosity, what exactly is water injection?

 

Injecting an atomized mist into the intake charge can help keep intake temperatures and guard against detonation. You can check out a real description at http://www.aquamist.co.uk .

 

I'd heard Water Injection effectively lowers the octane of your motor when in use, But the effects are small because you aren't injecting it all the time. It is used to cool (water turns to vapor) in the combusion chamber to give you better combusion, this is only really a problem in cars with really high compression or as Ace said Turbo charged cars. Most people mix 50/50 water/alcohol.

 

If your tuning is good it's not really necessary.

 

I agree. If you are using Water Injection, you've probably gone too far.

 

For most people the money could be spent on something else, like a nice vacation.

 

my buddy used to use some water to clean the carbon off the inside of the motor... not sure if worked or not.... lol

 

Used water injection on an old Ford F150, motor lasted forever and was pretty darned clean when we tore it down.