SV: Flow rates for nozzles

[Roland Johansson]

Usable pump could be a waterpump from the headlight washing
system. One or two of these pumps could probobly make a pressure
of 3-4bar even with moderate flow. These pumps can't cost to
much.



Roland Johansson
Scirocco 1,6l TIC -82

> > 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