Water Injection, how much water?

[sergei]

I'm building a water injection system for my GT4, I'm going to use a high pressure pump, cold start injector, MAP sensor,and a microcontroller...
The problem is I don't know how much water I have to inject (vs boost pressure and maybe RPM). I can measure the cold start injector flow at 100% duty cycle, and derive the amount of the water to inject...

So, with aquamist system I assume there is only fixed amount of water being injected after certain boost level. Does any body know what sort of flow of water is injected?

[Mr Revhead]

some good links here:

http://www.waterinjection.co.nz/

[sergei]

right, so on safe side I should do about 10% of fuel, so with my 100cc/min coldstart I would need 1 to 1 to fuel injector duty cycle...
This makes my uC firmware much easier, just input the duty cycle from fuel injector(s) and ouptut it to water injector, with a 1d map to switch it off under 1bar of boost...

[slonlo]

could be worth checking if the cold start injector will work long term running water. wouldnt want it to corrode up and do some damage

[sergei]

I will make rig to simulate the operation, I still have to measure the flow it outputs. If the cold start injector will not work, I will use a solenid (probably boost control, it has got alloy internals) and a fine jet. BTW where I can get the sprayer suitable for my application?

[sergei]

Or, maybe, one of the ST205WRC/GROUP A owner want me to sell their water injectors (located in same place as cold start)? Assuming they are functional from factory ....

[Stealer Of Souls]

autospeed had a good setup for ic sprayer. It used a very fine spray nozzle. Perhaps that could be of use to you.

http://autospeed.drive.com.au/cms/A_2720/article.html
http://autospeed.drive.com.au/cms/A_2719/article.html

They also used suitable water pump. Same type as used by aquamist, but it's only AU$95 plus about AU$50 for a suitable power supply unit.

I can get PDFs if needed.

[strx7]

I will make rig to simulate the operation, I still have to measure the flow it outputs. If the cold start injector will not work, I will use a solenid (probably boost control, it has got alloy internals) and a fine jet. BTW where I can get the sprayer suitable for my application?

I Imported a couple of W/I pumps outta the US capable of pumping 150psi. I also found a guy in the hawkesbay who sells suitable nozzles. I have his e-mail addy at home. which I will PM you tonight.
he carries two different nozzles, 1's flow is sufficient for 1 nozzle per port runner set up, the other is suitable for 1 or 2 to supply the entire engine, depending on how much you need of course

10-15% of fuel flow seems to be the going rate

[Wildcard]

You can buy jets directly from www.waterinjection.co.nz also, I run a 1.0mm jet on mine which gives ~15% water/meth to petrol at full boost/rpm.

[strx7]

the nozzles i found are $7 + gst each

[sergei]

I have a diaphragm type pump, supplying about 6bar pressure. So pump is not a problem....

[Stealer Of Souls]

What flow rate are you expecting?
That vibrating pump can dish out 15 bar @ 100cc/min, and drops pretty linearly down to 2 bar @ 500cc/min.

Also what car?
Something to consider. If you're running turbo then the pressure differential across the nozzle will be less. The 6 bar pump could drop to around 5 bar or less depending on the boost you run.

More pressure = better vaporisation = better performance.
Could mean lower flow rates, which means water lasts longer.

[sergei]

The car is ST165 with CT20b, so for me ~150-200cc/min is just right (440x4=1760cc/min max of fuel), boost is arrroung 16-18psi, will turn on water injection after 1bar. The plan to inject depending on fuel injector duty cycle vs boost. the pump flows ~ 9l/min at ~35psi, more than enough, it is not a little window washer pump...

The control algorythm:

while(1){
while(boost >1bar){
if (rpm<5000rpm) {
water_duty_cylce = fuel_duty_cycle+correction;
}else{
water_duty_cycle = 100;
}
}
}

So when 1 bar is reached I will have water injection injecting water at same proportion as fuel if rpms are under ~5000, if rmps are over I will have water injection completely on, as neither cold start injector or water valve solenoid will not be able to open that fast (~5ms opening time)..

[cosi]

what kind of microcontroller are you going to use?

[Stealer Of Souls]

why the outer while loop?
Is this just legacy leftover from your test script?

[sergei]

AVR AtMega32, the while loop is just the habbit...
While it is overkill to use AtMega32 for just WI, I have plans for it which include 128x64 LCD+ data logger (to SD Card), thats where lots of 10bit ADC come handy (as well as PWM), interface to wideband sensor, 5th injector controller, and maybe implement my own boost controller.

[matt dunn]

My aquamist setup injects 250cc/min at anything over 8 psi.

As for fuel flow, I run 4 x 600cc injectors at 80 to 90 % wot at 20psi,


Matt