Water injection question

[BuffaloGuy]

I've just installed a water injection system and I'm having a little problem with the Hobbs pressure sensor.

I've got it wired so that when it closes the switch (@ 10psi) it sends power to the pump and light on my dash.

The problem is that when it hits 10psi the light starts to flicker. With more boost the light gets brighter until and about 14 psi it's fully lit. Shouldn't it just light up all the way at 10psi?

I thought I had a defective Hobbs switch but the replacement is doing the same. If I wire the power right to the light the light is solid and bright so it has to be the switch.

Any ideas what could be doing this?
Ken

p.s. I sure can feel when the H2O kicks in!

[JoeyD]

I would pull the light out and clip on a multimeter to the wires and check proper voltage. It may be the light.

[Spindrift]

Ken,

It's not my intent to heist your original post but I couldn't help but notice your signature. How did you replace the snorkel?

[roclongrider]

Spindrift,

You don't replace them, you remove them! :D

[Kennedy]

Likely switch "chatter" until it hits enough psi to fully activate...

[markrinker]

Buffalo Guy -

What brand of water injection system did you install? Would you recommend it to others?

[JohnC]

Originally posted by kennedy:
Likely switch "chatter" until it hits enough psi to fully activate... Yes, and sure sign of short life for the switch. Hobbs switches are typicaly used in a configuration where the normal operating pressure is significantly higher than the switch setting, like a 10 psi switch in a 40 psi lub oil system. A turbo system doesn't really have an "average" operating level and as such the switch can be operated right on the edge of it's switching pressure, resulting in this behavior.

One thing to try is raising the set pressure to the point where the switch only closes when you're hard on the throttle, assumung you're going to stay there for a while. Also, add a relay to remove the electrical load from the switch contacts. Idealy, some sort of "debounce" circuit would keep the switch or relay from chattering.

[moondoggie]

Good Day!

I have no idea what a Hobbs switch is, so this may not apply. That, however, has never stopped me

[BuffaloGuy]

Thanks for the feedback guys. As for the idea about the boost dropping the pressure and there-by opening the Hobbs switch - It actually works the other way. I've noticed increased boost when the water kicks in so that rules out that solution.

JK and JC - I think you guys might have hit it on the head. The switch is chattering because the switch is working on the edge of it's limit.

Is there another switch that would do what I want? It seems like no matter what I do with this switch it's going to trash itself and possibly the pump too. Not to mention the poor performance in the meantime.

I need a switch that closes completely when it senses 10 psi. Any ideas?

FYI. The system I installed is of my own making. I did get the nozzle & holder, check valve and some methanol rated tubing from snow performance. Nice guy and very helpful. He's at http://www.snowperformance.net/default.htm

The systems are very simple and can be put together for about $200. Go to http://www.turbomirage.com/water3.html
and check out a good site for learning the ropes.

I haven't had much a chance to use the system yet so I can't give a report with confidence yet. Now the truck is in the shop getting the tranny and transfer case worked over. I promise to give a report after I've pulled a load or two.