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View Full Version : poor atomization below 20% duty cycle


turboii
21-05-2012, 01:29 AM
i am new to water injection, and i just finished installing and testing my HFS-3 system in to an FD3S and i have a couple questions. I am controlling it with a PWM output from a haltech PS1k, with can be fully mapped 0-100% duty from an rpm vs boost table. Nozzle size is 1mm, and i am just spraying straight water.

What is the best switching frequency to use?

also, I had the nozzle set to spay into the air, and noticed poor atomization below 20% duty cycle. in fact, nothing would even come out below 16%, even though the pump starts running at 12% with the threshold turned all the way down. I tried several different frequencies, from 30 Hz up to 200 Hz, and didnt have much effect on results

so why the poor atomization at low duty cycle? when i tested it, i used the full run of smaller hose (FAV to nozzle) that came with the kit, would a long hose run cause it? I would think with something operating at over three times the pressure of a fuel injector would be a little more precise?

Howerton Engineering
21-05-2012, 02:02 AM
The long length of hose has a significant affect on the spray. The best results are seen with the shortest possible hose length. Without more info on how you had it setup, it's hard to say what was affecting the quality of the atomization and what you were seeing.

It typical user range is 20-80%. As you go above 80% you have closing time issues, similar to a fuel injector going static, and below 15-20% opening time issues. This is for an out of the box kit.

If you want to be able to map to the extreme of duty cycles, the system has to be setup to do it. I.E., Short lengths of hose( a fuel injector has none) and the valve should be matched to the jetting size used.

You can see in this link (http://howertonengineering.com/blog/page/3/) ( scroll down to dual FCM system) we ran from 100% down to 20% with perfect atomization with 3000cc of jetting.

Richard L
22-05-2012, 03:43 PM
Here is another video of the system, duty cycle starts from 0%.


http://www.youtube.com/watch?=1&v=_HQMTfybwaA&feature=endscreen

and response time:

http://www.youtube.com/watch?v=xvSNmn6A64M&feature=relmfu