Flow rates for nozzles

[Barry E. King]

> -----Chris C.'s Original Message-----

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

This is what I am not sure of.  Seems to me the kits I have seen are much
much lower than 50%.  I am wondering what range should be considered usable.
I read one study that worked with 5-15% based on mass.  Also the nozzles
that come with a number of the kits I have seen would be limited to more in
the 10-15% range, but I dunno.  This is something I need to determine.  I'd
prefer to not use trial and error to get into the ballpark.  Do you recall
where you got the 50% number?

> 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).

Since the manifold will be at relatively high boost anyway I am hoping this
isn't too big of a concern but it is definitely something I need to watch.

> 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. :)

I plan to pulse the water injector at some proportional rate and have it
adjustable based on MAP.  Save a buttload of coding and even some hardware.


> My questions are 2:
>
> Will an ordinary (gasoline) injector live happily squirting water?

Sounds like maybe a bit of machinists oil will help here.  We'll see :)  No
loss if I toast these injectors.  Besides which I have 6 of them. ;)

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

I too had this question and I think maybe the answer is "not likely"
dependant upon the purity of the water.  I now plan to use a pump designed
for water.  They still won't be that cheap I suspect at the pressures I
think are required.

> 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.

I plan to cycle the pump also to allow for adjustable pressure.

I am thinking an el cheapo PIC 16C84 will do the trick since there is not
much work to be done and a very small amount of code to write.  I will need
ADC for the MAP but I could use a chip for that if I get lazy.

Next on the gadget list is to come up with a good algorithm for an
intelligent self-learning boost controller coupled with an intelligent
blow-off valve.  Then I could tie the water injection controller into the
boost controller to limit boost when the water reservoir is empty.  Too many
ideas.


Regards,

Barry