# Would this be possible? Boost and MAF activation.



## Fast VW (Sep 24, 2002)

I currently have a Snow Performance stage 2 set up that is using MAF to determine injection amount. This is on a MKIII 2.0 with a NS S/C. The problem I have is that in order to fight detonation in the lower rpm range I must start the injection around 2.6v. This works great on a flat surface either cruising or WOT. But if I am cruising at highway speeds (70 - 75 mph) and start to climb a hill, the water will turn on. I can fix this if I turn the start voltage up but then I am back to detonation in the lower rpms while under boost.

Would it be possible to add a manifold pressure switch so that the controller didn't receive power (it couldn't turn on) until a certain level of boost was reached (maybe 3 psi)? I figured if it was possible after hitting 3 psi the controller would determine the injection amount based upon the MAF voltage.

I have tried running the controller off of boost but I cannot get a good injection curve with it. It seems that I do not get enough increase in water between 4000 to 5500 when based upon boost.


----------



## BLSport (Dec 24, 2005)

Fast VW said:


> Would it be possible to add a manifold pressure switch so that the controller didn't receive power (it couldn't turn on) until a certain level of boost was reached (maybe 3 psi)? I figured if it was possible after hitting 3 psi the controller would determine the injection amount based upon the MAF voltage.


Seems logical, sounds like this could work.



Fast VW said:


> I have tried running the controller off of boost but I cannot get a good injection curve with it. It seems that I do not get enough increase in water between 4000 to 5500 when based upon boost.


What injection nozzle(s) are you currently using? Did you try dialing back the max injection point to less than your full boost pressure in an attempt to compensate for this?


----------



## Fast VW (Sep 24, 2002)

I am currently running a single 175ml nozzle. I have tried turning the full back but I run into 2 issues. The first is that I am injecting before the rotor group so my boost level can actually change some according to when and how much I am injecting. The bigger issue is on the controller the area I need to adjust in is not very easy to accurately adjust. The difference between 4lbs and 8lbs is about 1/32 of an inch. Not very user friendly on lower boost adjustments.

I called Snow Performance to get their input on the manifold pressure switch idea. They said that their controller is "too smart" and will "know that something is messing with it.":screwy: They said best option was to upgrade to a stage 3 controller so injection could be based upon injector pulse width, for $380.


----------



## BLSport (Dec 24, 2005)

As you noted, the adjustment dials on the controller are not so user-friendly in their scale and accuracy.

For precision, I make all of my adjustments by applying controlled/monitored pressure to the injection controller, and reading its output voltage; I've mapped out several different combinations of start/full output points for my particular setup, in increments of 1 PSI, from start output point to full output point for each combination.

I'm curious about the inner workings of the MAF-based portion of the controller, and what it would do in response to "knowing that something is messing with it". Its only input is voltage in this mode; perhaps it responds differently to seeing the input voltage start well above zero (relatively speaking). If this does affect the controller, I suppose you could interrupt the controller's output voltage instead; i.e., a relay between it and your pump, triggered by a manifold pressure switch.


----------



## ryan mills (May 3, 2002)

Just take the green wire feeding the pump and interrupt the signal with a hobbs switch set at 3 psi.


----------



## bwyatt079 (Jul 20, 2006)

isnt this what the snow performance "safe injection module" is for?


----------



## BLSport (Dec 24, 2005)

bwyatt079 said:


> isnt this what the snow performance "safe injection module" is for?


That module monitors water injection fluid flow, and triggers an alarm/provides a 12V output to control a failsafe device/method (boost-cut, timing retard, etc.) if flow falls below a set value.


----------



## bwyatt079 (Jul 20, 2006)

oh ok so as long as it sees a good flow, it doesnt care what the maf/boost levels are? i thought maybe it could determine that a higher flow was needed if the maf numbers got too high and then adjust timing from there...


----------

