Using TPS signal to engage Water Injection
 

My Cooling Mist water injection is currently setup on a pressure switch which engages at like 1 psi (roughly 4500 RPM in my application). I also have a toggle switch setup to turn on the water injection so that when I'm cruising at partial throttle, I can switch on the water injection and kill the ridiculous heat soak I get.

There are obviously inherent problems with each of my methods. In order to get the 1 psi, I have to "lean into" the throttle a bit, and for the WI to do any good, I have to stay in the throttle long enough for it to spray a significant amount of water. Usually, this involves going much faster than I need to, and isn't exactly practical.

My switch method works decently on the Interstate when I'm cruising at partial throttle because I can turn on the switch and cruise and watch the temps drop like a rock. The problem comes when I get off the interstate and drive around town (most of my driving). I can't be down there switching it on and off and drive safely. I've found that the throttle plates need to be partially open (30% or more according to the S-AFC II) for the WI to significantly cool the intake temp sensor that is just infront of the throttle body. This is likely due to the flow of air.

Basically, the best of both worlds would be to have the WI enabled when I'm at 30% throttle. I do not have a very large jet, so I don't have to worry about bogging. Now, this is the part where I get a bit foggy. I know that the TPS sends an electrical signal based on the amount the throttle is opened. Somehow, I need to use that signal and convert/connect it to a switch that will ground the pump and activate the solenoid to run the water injection.

You may not agree with what I'm trying to do, but please just assist me anyways to amuse me. I think it is a legitimate attempt to cool my 160 degree, non-intercooled intake temps.

Thanks.

Sounds like to me you are using a water spray on your intercooler? WI would be used under boost to reduce detonation and unless you are taking manifold temps you would not see a drop. So if I understand you, you are spray the cooler?

Being that the TPS does not have a on off ground or 12V I do not see how you can do it. If you find something that does have a brake you can run that to a relay. What you can do is get a VSAFC and use the RPM based output to your WI. To go a step farther is you want it for cruise you can run a relay to your 5th gear switch on the tranny and when that engages it turns over a relay and at this point the VAFC is already anticipating its job and then you are spaying.

No, I have no intercooler. I have a Cooling Mist Water Injection kit that has a jet tapped into the elbow of my supercharger inlet between the supercharger and the throttle body.

What kind of signal does the TPS send then?

I wonder if you can get a relay or somthing that operates at around 2v or so. only because that TPS I think would be around where you need it to be to activate the water system at 2v. I dunno im just shootin ideas

Yep, that's what I'm thinking. I'm sure one of the electrical gurus will step in here soon.

The TPS runs on resistance from 1 ohm to 5ohm what im getting at is you need a on off signal or a braking signal and that will not come from the TPS. So you are back to hunting for a method of a VAFC type device.

Or upgrade to mega squirt 2.0+

don't worry about the TPS setting.. your water injection should be controlled by the boost pressure...

The reason it seems to take a long time for the cooling affect to happen is that you are not seeing the change in the intake air temp.. you are seeing the effects of EVAPORATION ON THE SENSOR!!!!

You are also falling for the myth that water injections main funtion is to cool your intake temps.. Its actually designed to cool your cylinder walls and prevent pre-ignition from hotspots on the metal when the intake charge is being compressed.

It is also designed to cool the CHARGE temp while the charge is being compressed.. As the air charge is being compressed, its temperature skyrockets, the water mist contained the the charge get turned to superheated steam, thus cooling the charge and preventing hotspots whithing the charge from detonating.

Your best bet is to keep it the way it is... adding water at partial throttle and no boost is NOT a good idea....

If your spray nozzels are misting nicely, the water injection is doing its job, regarless of what your intake temps are telling you (you'd have to have a charge temp display.. and I have no idea how in the hell you'd get a sensor INSIDE the rotor housing :) )