Flow rates for nozzles

[Bruce Plecan]

-----Original Message-----
From: Barry E. King <beking at home.com>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Friday, December 18, 1998 9:24 PM
Subject: RE: Flow rates for nozzles


>> -----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.

50% is from Sir Harry Ricardo's Book as a max number, and what
we use in a max effort pulling tractor running 60 PSI of booost.

If non intercooled, and your looking to help cool the intake air charge,
then I'd go with the finer the mist the better.
>
>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. :)

Fuel consumption from max torque to max HP is increased by only
a couple percent per K of rpm, so it don't have to be very precise,
>
>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
>