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Wiring - Primary Arming Switch, WOT Switch, and Solenoids
Wiring a nitrous system can be intimidating, especially when adding an RPM window switch. The adjacent schematic shows the basic wiring per the Zex instructions (schematic does not include RPM window switch). I've broken down the wiring into two phases for the sake of simplicity. In this section I'll handle the primary arming switch, WOT switch, and both the fuel and nitrous solenoids. The next section will cover the RPM window switch from the HyFire 6.6 box.


The included WOT throttle switch uses the same type of bracket used for mounting the fuel and nitrous solenoids.
 
I planned to mount the WOT switch and bracket on the rear driver's side carburetor stud. Turns out I needed a longer stud to make it work. I pulled the carb and added a single 1-1/2" carb stud in this location.
     

It wasn't pretty but it was solid. The bracket required a good twist and turn to work. You can see that at WOT, the carb linkage would make contact with the WOT switch arm.
 
Remember this shot from the bottle heater section? The paired red and white wire from the primary arming switch would come into play now.
     

Here's the pair routed from the console and just above the passenger floor board.
 
I threaded the white wire through the firewall and headed for the WOT switch.
     

This shot shows the white wire from the primary arming switch attached to "Post 4" on the WOT switch. The red wire from the primary arming switch was connected to a 12V Key On terminal on my auxiliary terminal block.
 
Now it was time to wire the fuel and nitrous solenoids. Neither solenoid had specific polarity. Either wire on each solenoid can serve as that solenoid's ground wire.
     

I joined one wire from each solenoid together with a single wire and ring terminal for grounding on the engine block.
 
Here I found a suitable firewall location for the included and necessary relay.
     

I made up this red wire to run from "Post 1" on the WOT switch...
 
...to "Post 1" on the relay.
     

Next, I joined the two remaining solenoid wires for a run to "Post 3" on the relay.
 
The relay needed 12V straight from the battery.
     

That same 12V wire required a 30 amp fuse.
 
The now fused 12V battery wire was connected to "Post 5" on the relay.
     

I made up a ground wire for the relay...
 
...and connected it to "Post 2" on the relay. I used the same engine block ground location that I used for grounding the solenoids.
     

With basic wiring done, it was time to test the solenoids. Agani, no need for the nitrous bottle to be opened or the car to be running.
 
With the key in the on position and the primary arming switch on, I manually depressed the WOT switch and confirmed that both solenoids opened up. The "click" was easily identifiable.

Wiring - RPM Window Switch
As mentioned in previous sections, a proper and safe nitrous system requires a RPM window switch. This "smart" switch prevents the nitrous from being activated at too low of an RPM. Think of an unexpected bog at wide-open-throttle. The nitrous setup to this point has no precaution for engaging the nitrous during a WOT and low RPM condition.


The Mallory box specifies this violet wire originating from the connector shown as the RPM window switch wire. The Mallory box is a "ground" based system. This means, the switch is active when it is grounded. Confusing? Let's show you how easy it is.
 
I temporarily ran this long red wire (the one I connected to the violet wire in caption 1) outside the car and toward the firewall mounted relay I worked with in the previous wiring section.
     

I pulled the relay grounding wire from "Post 2" that I had made up in the previous wiring section...
 
...and simply replaced it with the single RPM window switch wire from the Mallory HyFire ignition box.
     

For testing purposed, I set the RPM window switch to activate a 1500RPM and shut off at 2000RPM.
 
With the motor running, I slowly ran the throttle from idle to 2500 RPM while manually depressing the WOT switch. I clearly heard two clicks, the sign of a safe nitrous system.

Next Steps
At this point, since we were only running a 100HP shot, the system was ready for a road test. You may have noticed that we didn't get to wire the HyFire for the necessary 4 degrees of timing retard during the RPM window switch operation. This could be handled mechanically for now. A road test and final retard wiring will be addressed in a short follow-up to this article. For now, what you have read and seen in the pictorials shown in this article can be considered a fine reference for a first time nitrous system.


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