Water meth control thoughts

[oldpoopie]

Im refreshing my water meth setup (devils own) and a thought just popped into my head. Would it be possible to control the pump directly with the factory ECU, perhaps use the N18 egr output?

 

[TDIMeister]

If you want to use some ECU signal, I would use a control strategy that opens past a certain threshold of N75 duty cycle instead. But this would require a separate box because the raw N75 signal for VNT engines are highly dynamic and opens up at useless times as far as WI is concerned (e.g. lift throttle), so more intelligence and logic are needed. {Edit: Recalling Fix_Until_Broke's thread some interesting plots showing N75 duty cycle, I got mixed up as to vanes closed/open during lift-thottle while shifting}

EGR is disabled at high load, precisely where you want WI. On the other hand, could one overwrite the EGR map and replace it with a WI map and use N18? Ostensibly yes. If actually possible, this would be ideal, that is, assuming that your car is for off-road purposes only...

Looking at where WI does any benefit, it's at high RPM and high load. More directly relevant to probe and use to trigger WI are smoke/torque limiter maps.

Otherwise, a strategy based on EGT/EMP would make the most sense.

 

[skyking1]

is it currently boost controlled?
I have an AEM syetem on my dodge diesel that I am contemplating moving to the beetle. It has a boost sensor in the control module.

 

[oldpoopie]

Yes, it's controlled by a progressive controller made by devilsown. It works fine, I'd just love to clean things up.

Tdimeister, that's exactly what I was thinking. Load a map to replace egr that will control water meth based on load and rpm. What would I need hardware wise to do that? I doubt the pulse coming directly from the ecu could support the draw of the meth pump.

 

[skyking1]

Good luck with your quest. Where did you hide your reservoir/pump?

 

[oldpoopie]

Reservoir uses washer fluid tank, pup is just below where the stock smic would be

 

[skyking1]

cool, thanks. I used the truck's washer fluid tank as well. I was thinking of using the space inside the right rear fender, accessed by the tail light. I would put a filler inside the diesel filler lid for it.
sure it would take time to purge, but once the line was full it would work OK, IMO.

 

[chapelhill]

Given you already have progressive controller I think easiest way is to use a boost pressure switch to switch on and habe progressive controller sent a voltage proportional to rpm. My data logger is able to determine rpm from tapping on pd injector loom so should be some easy diy circuits to be able to convert to analogue voltage. I just use the progressive as a soft pressure switch.
Even if you get signal back out of ecu for n18 you will still need a circuit to convert to analogue voltage for controller or could you just drive a solenoid for water injection pump?

 

[kilner]

if only you had the ppd 1.2 ecu you could then controll it from the swirl flap map

 

[Fix_Until_Broke]

You could probably use a solid state relay between the N18 signal and the motor. Many are rated for 20A. Throw a flyback diode in on the motor side so it does not kill the relay with the inductive kick and you should be good to go.

As far as a map goes, you'd have to manually figure out what boost you're running at a given load and then determine how much duty cycle you want to run the pump at.

Ideally though, I'd think you'd want IAT as your feedback signal to control the WM injection. If it's 3F outside and your IAT's are 45F, do you care or really want to consume WM in this case? On the other hand if it's 94F outside you might want to run it more frequently.

 

[skyking1]

sounds like a good plan if you want full automation. I mistakenly put an IAT probe in the manifold itself, which of course suffers from a little heat soak up from the engine and is slow to cool. easily fixed with a 1/8" pipe plug

 

[ocshaman]

You could set the system up Aquamist style and use the ECU for solenoid control. Turn the pump pressure down to 160psi or lower, have the pump kick on when the car's ignition turns on, and use the ECU (if possible) to supply a 20-30hz pulse. If that isn't possible, use the ECU output as a 1-5v signal and use minimum signal as maybe 2v (minimum signal input to activate DO controller), with max at 5V.