controlling water flow
 

I know that swtched - or staged water injection systems are not very smooth in their operation, so i was wondering along the line of the above post- adjusting the voltage to the water pump to controll the flow- in reference to boost pressure using a pressure transducer and an electronic circuit. Say for example the pump turns on at 2 psi- with 9 v dc- then inceases to full voltage at maximium boost to13.8 v. Would this work ok- or would it kill the pump over time. Or will it need a refernce to rpm signal as well to give good water flow control. this could be done off the coil probably.
What do people think? The initial sytem could be pretty easy to setup.

Brad,
I had wondered wether it would be smooth enough as Ive no experience with this sort of thing. Im currently adding some code to my ecu to switch a valve from 80% duty cycle to 100% as boost increases from 3-6 psi. It will still be stepped but in 0.5psi steps. This will need some work before it is finished so will end up with my first idea to start with then change to this later. One question for you, any idea what sort of frequency the Aquamist fast shutoff valve works well at?
Thanks,
Phil

Philip, The high speed valve will operated at the same frequency as a fuel injector. It wil operate up to 250 cycles per second. It can be driven with the same map as the fuel to start with then modified for the most perfect fit.

Brad,
hadn't considered doing it that way, that would have been easier for me. Can soon change code for that. Do you know what sort of drive I would need for the valve? i.e. is it the same as turning an injector on/off, or can I just drive it with a standard power transistor?
Phil

Yes it can be driven in the same way as an injector on/off. It is a solenoid valve - 13ohm coil resistance. Normally closed that opens when the circuit is charged. A fused 12v+ source with a switching ground will drive the solenoid. It has an transition change time of about 1ms from fully closed to fully open and vice-versa.

The Aquamist highspeed valve 806-244 is a 13ohm resistance valve. If you driver will do high impedence you are done. If you have a low impedence driver you would have to a FIA2 amp to convert the low impedence drive to drive the high impedence highspeed valve.
If you are using peak and hold injection the FIA2 will convert that signal into a standard duty cycle to drive the highspeed valve.
The highspeed valve with a constant water pressure supply is the most tuneable setup.

Hi,
no im not using peak and hold as my injectors have external resistors so this is not needed. So what your saying is fire the water valve when the injectors are fired? So do you then increase water pressure to tune the amount of water or do you need to increase/decrease the Pulse Width to tune? Just had a quick calculation and all my injectors will fire 1500cc/min of fuel, so If I fired a 150cc/min nozzle at the same time as the injectors then I would get 10%, Yes?
thanks for all your help,
Phil

Yes you will fire the highspeed valve with the injectors. Changing the pulse width changes the flow, use a 1.0mm nozzle or you may have to move up to 2 0.9mm nozzles for high horse power. The high speed valve will not require a resistor. Keep water pressure constant.
You will be running the water injection just like a fuel system.
If you elect to not use a different map for the water then you will change jet size to create the balance between fuel, air and water.
You math is correct on water fuel ratio.

Brad,
that sounds too easy, will order a few different sized nozzles and try them out. How do you know when youve got it right? Obviously water/fuel ratio is easy enough to do but when do you know that you carn't add any more water?
thanks,
Phil

The engine will get a little quiter when correct and power will be better. At some point you need to put too much in. Increase flow until the car stubles, that will be too much. Then work down to best power. The main reason for making the car run bad is so you know what that feels like. If you tune the car on a hot day and then the weather turns real cold the car will run bad.
Basicly it is by feel or on a rolling road.