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Directly driving a W2A pump


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Hi. As the title says, I'm planning to use a G4+ Thunder to drive a water pump in a W2A system.

The pump I plan to use is one from a BMW M2C, and per the documentation, it draws 6-7 amp.

Now I could wire a relay and get it over with, but in the interest of keeping things clean and simple I was wondering if I could wire it up directly to the ECU.

I reckon an INJ or IGN output could be used for this purpose. Can somebody confirm? In case 6-7 amp is too high for a single output, could I join two of them together to supply the required current?


Thanks in advance.

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41 minutes ago, neil brown said:

Injector output is limited to about 2 amps max

That would be Ignition output.

Injector outs can deliver a max peak current of 10A. I'm just not sure if they can hold 7A continuously.

I reckon eThrottle outputs could support this.


6 minutes ago, Confused said:

I'm using a pump from an X5, a Pierburg CWA50, for my water to air chargecooler.


I posted my settings in this thread here, hope it helps!


Thanks! This looks interesting. However, it looks like the PMU is handling power in your case while the Link only provides a control signal.

The pump I intend to use is a simple 2 pin affair that will kick on when a certain condition is true and remain that way.

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Yes, the ECU in my case is just sending a control signal. The main pump power is switched on by an ignition fed relay. Prior to this, I had a basic 2 pin on/off pump, which I used the relay switched from the ECU, so it only ran when the engine was running. A minor wiring change, I'm even using the same output from the ECU, but controllable nicely now.

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Thanks Adam. What do you think of:

1.  Using two combined injector outpputs and configuring them identically.

2. Using one of the eThrottle motor outputs.

Also, from what I gather, both the above outputs are over current protected, right? Meaning I should be able to experiment without frying something in the ECU?

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No you cant combine two outputs, if one wire ever has a bad connection it will put twice as much current through the single output.  If you fry it, it will not be covered by warranty.

Injector drives are very robust but have no active overcurrent protection as far as I know.

The E-throttle chipset rated continuous output current is 5A provided temperature is under control.  Active current limiting starts somewhere between 5.2 & 6.5A depending on temp.


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Thanks for the clarification Adam. I understand the warranty implications. Both my eThrottle outputs are free, and since you confirmed that they have active current limitation, I'll try combining the two of them.

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