Flow rates for nozzles

[Chris Conlon]

At 06:49 PM 12/17/98 -0700, Barry E. King wrote:

>> I hear (HI BRUCE) that about 1/2 the mass flow of fuel is about the right
>> water flow rate. I also SUSPECT that if you are getting GOOD
>> atomization of
>> the water, injecting it close to the intake valve, AND synchronizing the
>> squirt of the water with the inhale (high air flow velocity in the intake
>> port) that a water mass flow rate as high as 100 or 125% of the fuel mass
>> flow rate could have positive influence on HP output, particularly if you
>> go with a higher than usual static compression ratio.
>
>I need to mess around with the atomization aspect to see what pressure will
>do the trick.  I want to keep the pressure lower rather than higher just for
>cost's sake but will implement whatever works.

While I agree with Greg's comments about an *optimal* setup, I think the
simple system can give positive results, especially on a boosted motor.
Might I suggest that you *don't* want fine atomization, if you're going
to inject the water far before the intake valve? You want medium
atomization, coarse enough that most of the water gets into the cylinder
as liquid, but fine enough that it all evaporates inside. (Although at
25 psi boost, I don't think evaporating it all will be a problem!)

Water flow at 50% of the fuel flow rate (mass/mass) is the number I
keep hearing, not to say that other numbers can't work.

Water turning to vapor too soon (outside the cylinder) and displacing
charge air is a real concern, but the problem is perhaps less bad than
with the fuel itself. Mainly due to the much higher heat capacity and
latent heat of vaporization, but also due to the fact that most water
injection systems only come online at high mass flow rates. Finally
the water flow rate is not critical, you can increase it some which
will result in less of it vaporizing (to some extent).

The quick hack, which it sounds like you already have, is to just
monitor one of the existing injector wires, and use that signal
(buffered, of course) to pulse your water injectors. Choose your
pressures and nozzle sizes, and you're done, as far as the control
electronics go. Soooo easy. :)


My questions are 2:

Will an ordinary (gasoline) injector live happily squirting water?

Will an ordinary (gasoline) booster type fuel pump live happily
pumping water?

I'll probably end up with a different solution, a duty-cycle modulated
pump and nitrous kit fittings, but I'd like to hear how workable a
system using standard parts would be.

   TIA,
   Chris C.