PWM water inj question, controlling pump instead of valve.

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jon volk
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PWM water inj question, controlling pump instead of valve.

Post by jon volk »

Ive been running my WI as a standard on/off system. I want to go to a PWM system and use a solid state relay to control the pump, rather than a valve.

If doing it this way, would I be correct in selecting a "dummy" output for the pump in the software, say a CAN channel, and then switch the current pump output to the "valve" channel in order to get the proper output to the SSR?
shainiac
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Re: PWM water inj question, controlling pump instead of valv

Post by shainiac »

Jon,
You can use a SSR no problem. There are two outputs for water injection, pump and valve. Use the Pump output (GND) to turn on a relay to supply switched 12V to the pump. Use the Valve output to PWM the ground side of the "coil" on an SSR. The SSR connects the Neg side of the pump to ground.

So, if you're above 0% duty cycle, the "Pump" output will activate the relay so the pump sees 12V and the "Valve" output will begin pulsing the Neg side of the pump via the SSR. That's how Derek's turbo LS M3 is setup and we were seeing good atomization below 20% duty cycle with the nozzle spraying outside the car.

Are you using a Goldbox? Any of the Nitrous outputs can be used to PWM the SSR. If you're using a MS3X, you can actually use the mainboard injector drivers to directly PWM the pump since they're rated for the amperage.
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jon volk
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Joined: Sun Nov 28, 2004 3:12 pm
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Re: PWM water inj question, controlling pump instead of valv

Post by jon volk »

Yup, gold box.

The reason I say to use a CAN channel as a dummy output is that I currently have a 12v ign relay sending power to the pump relay. It's then triggered by the pump output channel which is assigned to FIDLE. To avoid any wiring changes, my thought was assign the pump in the software to a "fake" output, then pulse the SSR with the valve channel being assigned to FIDLE. Just confirming my logic is correct haha.
93supercoupe
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Re: PWM water inj question, controlling pump instead of valv

Post by 93supercoupe »

I think aslong as the relay that provides the pump power turns off with key power, you should be good to go.

In my e30, i had the pump power relay getting feed constant power and ground triggered by the MS. When i would shut the car off, the pump would activate for a second.

But that was using a main board injector output to PWM the pump directly. You might be alright going through the SSR and key switching the power on relay.
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jon volk
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Re: PWM water inj question, controlling pump instead of valv

Post by jon volk »

Everything seems to be working as intended this morning so I'm gonna call it good.
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