The parts consist of a cooling mist S-HSV cooling mist pump, and cooling mist pressure bypass valve, which effectively regulates the pressure put out by the pump.

Impressions, the S-HSV is very well designed, and it works.

It works fine controlled off the haltech, but I found it sensitive to PWM freq, and PWM duty cycle percentage, the higher the freq the more pump pulsing could be seen in the stream, a lower freq had the made the pump pulses invisible even at very low flow.

When I say pump pulses let me be clear, the pressure bypass switch is an electrical switch that turns the pump in at about 125PSI and off at about 130PSI. The pump tuns on and off fairly rapidly, when the valve is at 100% and and flowing 10GPH (a 10 GPH nozzle) the pump is pulsing about 10 times per second. This pump pulsing is only controlling pressure and not flow. At high flow pulsing can't be seen at all in the stream. At some point as the flow is turned down the pulsing can be seen in the stream, this seems to happen only when the flow goes well below a usable level. At what point the flow begins pulsing with the pump is strongly effected by the PWM frequency a lower frequency seems to provide better low speed control of the flow.

The PWM freq I settled on was 30 HZ, which is very similar to what a boost control solenoid switches at.

This seemed to give the most progressive flow rate of all testing.

The minimum usable flow seemed to be at about 35% duty cycle at 30 HZ, which gave a very nicely atomized stream with no visible pulsing. Steadily increasing the duty cycle up to 100% gave a very progressive increase in flow.

raising the freq also had the effect of changing where the minimum usable flow was available. With a freq of 400 HZ the nozzle wouldn't even produce a drop until over 50%.

If there was a pulsation dampener in the system (like the one in an EFI system) then a higher frequency would probably work better.

What I really need to do now is some tuning to see what I can do with this thing.

What I may do is create a chart by injecting water into a graduated cylinder at various duty cycles, (to determine the actual flow rate) I am guessing that the flow rate goes up with a curve as opposed to a strait line, such that doubling the percentage may not double the flow rate.

I think that this an all water injection systems that are designed to be progressive could benefit from an EFI style FPR, with a pulsation dampener, that would allow the pump to stay on as opposed to rapidly pulsed to regulate pressure. Perhaps a pulsation dampener alone would be enough.

I may adapt a bypass style FPR to this system to see how it works, I know of at least one that is designed to work with methanol.

I am very happy with the cooling mist products, especially the S-HSV and would certainly buy again.

I would also like to say the customer support given by coolingmist is excellent, he has been there and available every single time I called.