Window switch
 

Decided to go with this unit, Digital RPM Window Switch - 8969 seems to be the easiest to connect to the Zex NMU, any thought or experiences. Thanks, I know I've been hitting the forums hard with my dilemma and I really appreciate the help.:tiphat:

There is a fuel saftey pressure switch in the diagram but should help.

*Edit* wrong wiring diagram*

The diagram for the 8969 shows no need for a relay, I have no clue how to screen capture:shakes head:

my bad, I grabbed the wrong pic...

It's been a long day, I will try to find the correct one.

msd install pdf page 4

even better :icon17:

So what do you think, no relay and looks like the yellow goes to the white on the NMU?

It looks like relay pins 85 and 86 are the coil. This would mean that the yellow wire on the window switch unit goes to ground (energizing the relay) when the WS unit is powered up via the red wire.

Appears that relay pin 30 is the switch common with pin 87 being the NO contact and 87a the NC contact. This would kill the TPS signal to the ZEX if fuel pressure is too low.

If I got all that right, the white wire on the ZEX should be connected to TPS. Doing so will do away with the low fuel pressure cut-out.

Thanks for the reply. But the one diagram pictured is not for the unit I'm looking at. If it's not to much trouble, could you look at the pdf install for the 8969 digital unit. I could really use the help, this sh!t is driving me crazy.

If this would work I would even go this route Edelbrock Nitrous Systems
Digital RPM Window Switch
Catalog #71905
but in the wiring diagram it shows the white wire from the relay going to a micro switch, should I assume that in stead of going to a switch it goes to the NMU white wire?

Post links to schematics and I'll see what I can figure out.

Thanks for helping, here's two I'm looking at http://www.jegs.com/InstallationInst.../350-71905.pdf
http://www.jegs.com/InstallationInst...1/121-8969.pdf

White - Engine RPM input signal. 5-12V pulse. You can use the negative side of one of the coils or the signal from the ECM. See FSM for pinouts.
Red - RPM switch power. Get power from one of the fuse panels and use an on/off switch between the fuse block and the RPM switch. Mount the on/off switch anywhere that is convenient.
Yellow - RPM switch output (NO). Drive a relay with the output and use the relay NO contacts to switch the load (nitrous valve). Run one side of the relay contacts (NO) to the nitrous valve and the other side of the contacts (common) to a fuse and then a power source.
Gray - RPM switch output (NC). Not needed.
Black - RPM switch ground. Run to closest convenient ground.

The micro-switch (NO) is a WOT indicator to enable the relay.

Holy cow my head is spinning lol. I'm sorry please forgive me for my ignorance when it comes to wiring. So how do I incorporate the Zex NMU? This is for the Edelbrok unit correct?

The wire from the NO relay contact goes to the white wire of the NMU to tell it you are in the desired RPM band.
The micro-switch says you are at WOT and enables the system.
The fuel pressure switch shuts off the nitrous if you lose fuel pressure.

So, as long as main power switch is on, fuel pressure is high enough, gas pedal is on the floor, and RPM are in the target band, you will spray nitrous. If any of those conditions are not met, nitrous shuts off.

Without a main power switch, you may not be able to cut nitrous if the WOT switch fails closed.
Without a fuel pressure switch, you can continue spraying nitrous when the A/F is lean.
Without a WOT switch, you will spray nitrous whenever RPM are in target range.

OK cool so far I've got it except for the micro switch, the NMU has a built in TPS. So I don't understand the need for the switch.

The WOT switch is to keep the system from activating while you are getting ready to launch or driving down the highway. If the NMU is already looking at TPS, then the micro-switch may not be needed.

Edit: I'm an Electrician, not a "nitrous guy" so I may have misinterpreted the purpose of the switch.

You have it correct Ark. The NMU has the TPS there is no need for the micro-switch.

That's all good my friend, totally appreciate you time and help. You and Madwi have gone above and beyond to help me sort this out. Looks to me like a done deal, we'll see. Should have the unit by weeks end, everything else except the bottle holder will go in tomorrow.