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Water meth solenoid and pump control


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How doo, 

I'm trying to work out how to go about my water meth setup and how to control it. 

My original plan was to run the pump on a GP pwm output on a solid state relay but today I did a boost leak test and my check valve is rubbish so I'm thinking about running a solenoid. 

So my thinking was controlling the solenoid with the GP pwm and run the pump on a switch, is there a way to maybe have it so when the pump is turned on the ecu can up the boost and so on? 

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I dont have any experience with water injection to offer much advice on the merits of pump control Vs solenoid control but I can tell you that what ever way you go for you can do all of what you wish using standard functions in the G4+.  You would have the "pump switch" connected to a DI.  That DI could then be used to activate the solenoid (the PWM will still be controlled by a 3D table) and at the same time a second boost table and a second ignition table if required.

Edited by Adamw
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  • 1 month later...

Bit of a reproach to this subject.


The past few weeks i've been ironing out my map as the fuelling when the car cam back from the mappers was all over the place so had all that sorted. Now i'm ready to get the WMI set up and running. 

The equipment I have is:

150psi pump,

water meth specific solenoid,

solid state relay,

aem nozzle for engine up to 400bhp,

My thinking is have the pump wired through the relay and have the ecu power it up at a set boost say 0.7 bar (so its not running all the time) and have the solenoid controlled by a gp pwm output which will be setup to progressively increase duty as the boost increases. Does this make sense?

Ive also been thinking about putting a 200psi pressure sensor in the feed line to the nozzle and setting up a possible failsafe? maybe a pressure window of say 120psi to 160psi if it falls below or goes above that window the ecu pulls the boost? is that something that can be done?

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We have used the link to control a water meth table before, but not with a standard nozzle and solenoid. We used a Holley 1000CC Water Meth Injector and a Pump. The pump turns on with the ECU at a trigger point - X boost and X RPM. Then a second later, at X boost and X RPM the link sends a PWM signal to a Holley PWM module which controls the injector. The reason we used the Holley module is that the injector runs at 12 amps, and it would fry the ECU. We could not use a SSR in this application (we tried) but the frequency was not fast enough to be progressive. The SSR just "stayed on" when we tried to PWM control it at high speeds 

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