water injection? Ford's 182k plug change

[Edward Hernandez R]

Water injection's primary benefit is reducing combustion temperatures as it turns into steam, allowing more spark advance without detonation, as some have already posted. It doesn't alter air charge temperatures to a significant degree unless you are well above 100 C, which is possible and common with forced induction. BTW, forced engines would see higher gains by improving intercooler efficiency since water doesn't burn and displaces combustible charge.

Yes, it takes a lot of energy(heat) to do evaporate water, but it's usually worth more than the spark you would have had to retard. Alcohol was primarily an antifreeze with the side benefit of being combustible, but that adds heat that you are trying to absorb. Not enough of alky was used in water injection(which has it's origins in piston driven aircraft engines) to account for an appreciable drop in intake charge temperatures. 

For those designing their own, consider a MAP sensor to drive your systems based on an approximation of engine load. I know this can be more complicated than purely mechanical systems.  I have used the Edelbrock version for six years, and I've been pretty happy with it. It has a MAP sensor and reads rpm, allowing the user to adjust flow rate based on rpm and engine vacuum, and also the injection starting point. I like the one somebody in the list built which is driven by turbo pressure. Clever!

"The plugs had been replaced 1 time in 182,000 miles!"

Shhhhh! Next thing you know, everyong will want a 182k tuneup interval! :)

Ed Hernandez
Ford Motor Company
ehernan3 at ed8719.pto.ford.com