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ZEX Nitrous Kit Quick Installation Gude

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ZEX Dry Nitrous Kit quick install guide.

Section 1: Installation prep

First, make a note of all parts to be installed and the tools it takes to install them. There is nothing worse then holding a part with one hand and reaching for a non existent tool with the other. I started under the hood, the ZEX control box is small but really takes up a lot of room when space is limited. I found a spot right in the center top of the firewall, directly behind the intake manifold. Make sure your mount location is close enough to the intake for your nitrous line to reach. I had to move the clutch hydraulic line a bit lower but no big deal. After I was sure I had a place for the box I started on mounting the bottle. I am doing this install on a coupe so the trunk is an obvious place. I would prefer the bottle be on the right side to offset some of the weight of the driver however this was not possible to do and run the line the way I wanted. Before drilling any holes be sure to check under the car for the best route to run the cable, as this will affect the bottle location. On the '99 civic this kit is going it I chose to run the line from the trunk directly into the sub frame. The line then went around the gas tank and into the plastic housing that carries the gas vent and return lines. I used a lift to get under the car but the same thing can be accomplished with jack stands, if you don't mind laying on the ground.


Section 2: Line location and bottle mounting

The first hole I drilled was for the main nitrous line. Choose a location under the car and in the trunk that best suits the line. Avoid running it near any moving parts, also try to keep it as unexposed as you can as road debris can damage the line. I found it easier to drill up from the bottom, this way you can get around all the supports and avoid drilling down into them. In this Civic coupe part of the rear sub frame runs directly under where I want to mount the bottle so the line leaves the trunk and directly into the frame, completely unexposed. There is a small hole in the bottom of the frame rail I used to drill up through and into the trunk. After this was complete I mounted the bottle brackets so the bottle brackets. Do yourself a favor and use all stainless steal hardware. It will make removing the kit a lot easier if you choose to do so. After the bottle is mounted start running the line to the front. Make sure you cover the ends with tape before you do anything, you don't want dirt to get in the line and clog your nitrous system up.


Section 3: Piping

Running the line from the back to the engine bay can be tricky, plan your route carefully. Start from the back and drop the line down through the trunk. Pull out enough line to get you started but not all of it. Make sure you don't kink the line while pulling it from the trunk while under the car. Start working your way to the front of the car. You want just enough line to connect to the controls under the hood. Any extra line is best kept in the trunk beside the bottle. Again try to follow a line near the center of the car. Keep away from any moving parts and avoid using zip ties alone to hold the line as they will eventually break. I routed my line with out the use of any ties. Usually the fuel vent and lines are a good path to follow.


Section 4: Mounting the nitrous solenoid and controls

This is a ZEX system which makes installing all the controls easy as they are all contained in one single unit. All other systems fallow the manufactures recommendations for component placement. As I said before I chose a location on the firewall. Hold the box in place and mark the holes with a pencil. Drill your holes and mount it. I used stainless steal sheet metal screws so I did not have to get behind the firewall. I then connected the line running from the trunk and removed any slack under the car.


Section 5: Getting the nitrous into the engine

Select a place on your intake pipe to install the nitrous nozzle. The most optimum place is no closer then 6" to the throttle gate and no farther away then 18". If you can find a spot where the nozzle will shoot directly into the intake without going through any bends. If your intake is rubber or plastic, drill a hole a few sizes smaller then the nozzle so that it will fit snuggly. If your are running metal piping drill a hole and tap threads. Make sure you take the intake off the car!! You do not want metal shavings loose in your engine. A small bit of epoxy (JB WELD) will hold the nozzle from turning once screwed into the intake. Please make sure the nozzle outlet is facing in the correct direction (towards the intake manifold for you slow people). Connect the nitrous line from the solenoid to the intake. Only do this hand tight for now as you will be adding a jet to the line later.


Section 6: vacuum lines

Run the necessary line from your control box to the fuel pressure regulator. DO NOT USE A LINE T ON THE PRESSURE REGULATOR. The purpose of this line is to apply pressure to the regulator during nitrous use to allow more fuel to flow. If you add a T the pressure will just dump into the intake manifold creating a lean condition and engine damage. Use the vacuum port that the regulator was hooked to in the manifold to run the second vacuum line into the intake. During normal driving the vacuum will flow through the ZEX box and your fuel pressure regulator will function as normal. Avoid using cheap silicon lines, they make look pretty but without the addition of internal nylon braiding they may rupture under pressure. Also be sure to use a line clamp on the fuel pressure regulator. Most FPR vacuum hookups are no serrated and the line may blow off. Check all lines for snugness.


Section 7: Electronics

Be sure to disconnect the negative side of your batter before starting any wiring. This is fairly simple. With a ZEX system you only have to worry about 3 wires. Ground, power and the control wire. The ground should be hooked to a good grounding point, I chose to ground right to the screws holding the box to the firewall. The power wire should be run inside the car, through the switch, and to an ignition controlled 12v source. In most cars this can be found in the internal fuse panel. Probe around with a test light while turning the ignition on and off. The ZEX solenoid draws very fuel amps and should be ok to hook directly up to most any circuit. However, a relay may be used to draw power directly from the battery if this is a concern. Mount the switch in a location where it will not get bumped or accidentally turned on, and ALWAYS use a covered switch. I also installed a light on the circuit so I could easily tell when the system was armed.

Now its time to hook up the control wire to the throttle position sensor. In most cars there is 3 wires to the TPS. Ground, control and signal. You are looking for the signal wire. Hook up the battery and turn the ignition to the on position. Using a multi meter find a ground and test each wire. One should be a constant 5volts or higher, another a lower voltage, around .50 and the ground which will show no voltage. With the meter hooked up to the low voltage wire, move the throttle with your hand, it should rise to a point past 4.5 in the full throttle position. This is the wire you want, make a note of its color and turn off the ignition. Splice into TPS control wire and hook up the control wire from the ZEX box. When the box sees a voltage past 4.5 (wide open throttle) it will open the nitrous valve.



Section 8: Testing the system.

With the ignition on, arm the system and depress the throttle. You should hear a click from the ZEX box at or near wide open throttle. If you don't hear a click, check all your connections and make sure you are getting 12 volts to the box. Another possibility is that your throttle position sensor is not putting enough voltage on the control wire. The voltage must rise above 4.5 volts for the ZEX box to activate. Most TPS's run at 5volts or above, lower voltage may be an indication of a problem.


Section 9: The first run

Select the appropriate nitrous and fuel jets for your application. Lower is better for the first few runs, until your sure everything is working properly and you get the hang of driving with nitrous. Install the jets per the manufactures instructions and reattach a lines. Make sure they are tight, check all connections and slowly turn on your nitrous supply. Listen for any leaks, small leaks will be noticeable as the area around the leak will develop frost immediately. Arm the system and LETS GO! To be safe drive the car to second gear, make sure you do not push the accelerator to the floor as not to activate the system yet. Drive with the RPM's at about 3000 - 4500 and depress the petal to the floor. If your system is working, you will certainly know it. If you hear any strange sounds, knocking, pinging, bing bang boom, or the car starts to miss, let off the gas IMEDEATLY. If everything sounds good go with her! DO NOT HIT THE FACTORY REV LIMITER! Run the car to 1000rpm below the rev limiter while at wide open throttle then let off the gas. Disarm the system and check all the hoses and vacuum lines. Make sure they are completely snug and everything is operating properly. Make sure you do this after the first few runs to make sure nothing is starting to wear or break.


Section 10: Troubleshooting

What to do if you hear strange noises! Well, most likely it is caused be detonation, meaning the mixture is burning improperly in the combustion chamber.  The sound you hear might also be caused by preignition this means the fuel/nitrous mix is combusting before it should and usually means you are running to lean. Try running a smaller fuel jet to allow more pressure to the fuel regulator. In some cases other plugs may be needed. Do not be fooled, using a lower heat range plug will most likely not cure nitrous induced detonation. Try a plug designed to be run with nitrous, as they have smaller surface area to heat up.

To read more about detonation Click here

To read more about pre-ignition Click here

Your car starts to miss at high RPM's. This can be caused by too much gap in the spark plugs. The spark is actually blowing out before it has a chance to ignite the fuel. Try running a smaller gap or a hotter ignition system.