water injection

[Jim Steck]

>O.K., My daily driver (w/ 160k miles) is starting to knock unless I use
>premium.  I think I'll put in a water injection system, but have a few
>questions.  Can you dump in too much water?  I plan on a winshield washer
>pump, and to have it vaccum operated.  I will monitor the map signal and
>start pumping water when the engine gets below a certian vaccum.  What
>I could do with another op-amp and a 555 is have the water pump come in
>at 50% duty cycle at one vaccum, and full on when it drops below another
>vaccum.  I don't think I'll get carried away with using a pic chip,
>because I really don't know the relationship between engine load and
>knock.

A good treatise on water injection can be found in Sir Henry Ricardo's fourth
edition of "The High Speed Internal Combustion Engine" pages 165-171.  His
experiments were aimed primarily at increasing horsepower in supercharged
aircraft engines by way of controlling detonation (with water) so that higher
boost pressures could be used.  At high boost, normal fuel mixtures were used,
and an additional amount of water was added . . . up to 60% of the mass of the
fuel.  You shouldn't need nearly that much.

He also suggested that mixing up to 50% methanol with the water helped improved
its volatility.  

Jim Steck