Jumat, 04 Maret 2011

Installing a Nitrous Oxide System (NOS)

Installing a NOS kit is a simple process of installing the nitrous tank; a few injectors (which are also called nozzles); and a few solenoids; routing a few meters of tubing (or piping) from the nitrous tank and a fuel line to the solenoids, and the solenoids to the injectors; and then fitting a few switches to arm the electrical circuit that energizes the solenoids. If you are installing a Dry System, you don't need to run a pipe from your fuel line to the fuel solenoid as you don't need to install a fuel solenoid but you will need to modify your EFI system to provide the correct amount of fuel when you engage your NOS system. In my experience, the best way to install the nitrous system is to install the nitrous tank first, followed by the injectors and the solenoids, then connect your feed lines, and connect your solenoids to the battery. This will ensure that each of its elements correctly placed to operate at their full potential. If you are installing a Wet System, you must test the system and ensure that the fuel pressure to your fuel solenoid is constant and adequate. This may require that you install a high pressure fuel pump and/or a fuel regulator.

Begin by installing the NOS tank. The correct installation of the tank is important to getting the most out of your nitrous system. As we've mentioned in our basic nitrous system guide, the NOS tank has a siphon tube that extends from the release valve to the bottom of the tank. The siphon tube reaches the side of the tank on the opposite side of the label. Therefore the tank should be installed at a 15° angle, with the label facing up and the release valve facing the front of the vehicle. This will ensure that more of the liquid N2O is used before the siphon tube begins to pick up gaseous Nitrous Oxide, even under acceleration.

Another consideration is the pressure of the NOS tank. The pressure of the NOS tank will fluctuate as the ambient temperature fluctuates. This can cause problems with the correct calibration of your air/fuel mixture. To overcome this problem, you should ensure that the NOS tank is mounted away from heat sources (such as the exhaust system) and out of direct sunlight. You can also use a NOS blanket to insulate the tank.

You should install the injectors next. The placement of the injectors will depend on whether you're installing a system with a single injector, or a Direct Port System that requires one injector per cylinder. When you need just one injector, you should install the injector as close to the throttle body as possible. If you have a rubber inlet hose connected to your throttle body, you must drill a suitably sized hole to fit the injector, and bolt the injector down with a nut and washer on either side of the hose. If you have a cast aluminum manifold, you must drill a hole and tap a thread into the cast aluminum for the injector to screw into. If you are fitting a Direct Port System, make sure that everything that must be fitted to the intake manifold is in place and find enough space on the manifold to fit the injectors. The injectors must be fitted at the same distance from the cylinder head but try not to fit the injectors too close to the cylinder head. Also, wherever you fit the injectors, apply a little locktight to the thread to ensure that the injector does not work itself loose. If you are installing a Direct Port System, you would need to install a distribution block between the solenoids and the injectors. The purpose of the distribution block is to distribute the fuel and nitrous between the injectors. Although it is not crucial, try to install the distribution block so that the tubes are more or less horizontal. The injectors for a Wet System has two inlets — one for fuel and the other for nitrous. You must connect the right tube to each inlet as indicated on the injector.

The next step is to install the solenoids. These should be installed away from the exhaust manifold but as close to the nitrous injectors as possible. The solenoids must also be installed slightly higher than the injectors to ensure that the nitrous and fuel do not need to flow upward as this will reduce the effectiveness of the system. The solenoids are electrically operated; therefore you'll need to run a few electrical cables to the solenoids.

Once you have your hardware in place, you can install the nitrous and fuel supply lines. It is best to route the tubing that carries the nitrous to the engine bay along the stock fuel line as this would be routed securely, and away from heat sources. The tubing should be secured to the vehicle so that it cannot be damaged by abrasion or by moving suspension and drive train parts. You can use nylon tie-wraps to secure the tubing to the vehicle but ½ inch Tinnerman clamps work much better. The tie-wraps or clamps should be placed no further than 18 inches apart. Whenever you route the tube trough a metal body panel, be user to use suitably sized rubber grommets to prevent the body work from cutting through the tube.

If you are using nylon tubing, you can use a sharp utility knife to cut the tube to the correct length leaving about 2 inches of free play at either end for possible flexing. Never cut the tubing too short and never cut the tube using a scissors or wire snips as this will deform the tube and make fitting the olive and nut quite difficult. Once you have cut the tube to the correct length, slide the nut over the tube with the treaded part facing the end of the tube. Never tighten the nut too much as this will cause the olive to compress the tube and will restrict flow through the tube. Then slide the olive over the tube. Secure the nut to the outlet on the NOS tank while keeping the tube in place and repeat the process at the other end where you must secure the nut to the inlet on the nitrous solenoid. The tube from the solenoid to the injector will require the same treatment. You can install the tube from the fuel solenoid to the injector as well but don't secure the tubing to the fittings on injector just yet — you will need to perform a few tests first. Also beware, the injector for a Wet System has two inlets — one for fuel and the other for nitrous. You must connect the right tube to each inlet as indicated on the injector. Next, tap into your fuel line using a metal T or Y splitter and fit the tubing that will supply fuel to the fuel solenoid and connect it to the inlet on the fuel solenoid.

The final step is to install the electrical circuit that will power the solenoids. The NOS solenoid must lift the plunger against the pressure that can be upwards of 800 psi in the system. A fair amount of current (amps) is required to accomplish this task so make sure that the electrical cables can supply the required amperage to lift the plunger. The electrical circuit should supply both solenoids with power and should incorporate a fuse, a microswitch fitted to the accelerator linkage, an arming switch and a relay. Start by disconnecting the negative terminal from the battery. This will prevent you from causing short circuits while working on the electrical system. Run a live wire from the positive terminal of the battery to the fuse box under the dashboard and on to a relay. Another live wire can then be run from the relay to the relay to the solenoids. This wire must carry sufficient current to activate both solenoids. You can fit the arming switch on the live wire between the relay and the solenoids as this wire will run close to the dashboard area; however it is better to place the switches on the earth wire. The earth wire will run from the solenoids to a suitable metal point on the vehicle's body but it is best to run the earth wire to the negative terminal on the battery. You can fit the microswitch to the earth wire as the solenoids would be placed close to the accelerator linkage.

There you have it, you're done. All that's left now is to test the nitrous system and ensure that the pressure to your fuel solenoid adequate, and then tune the nitrous system for best performance.

Testing and Tuning Nitrous Injection Systems

by "Bad Ass" Bre (February 03, 2007)


Once you have your nitrous system installed, you must test the system to ensure adequate nitrous and fuel flow. This will ensure proper performance and reliability.

Start by ensuring that the fuel line is properly attached to the fuel solenoid and turn the fuel pump on. You can do this by turning the ignition key to the ACC position. Check for fuel leaks where you tapped into the stock fuel line and where the fuel line feeds into the fuel solenoid. Cure any fuel leaks, check again for fuel leaks and then disconnect the fuel line from the nitrous injector. Activate the system and check for fuel flow when the system is activated, and that the fuel stops flowing when you deactivate the system. If you don't get fuel flow, check that the fuel solenoid is operating properly — you should hear an audible click when the solenoid is activated; check that you have fuel flow at the fuel filter; and ensure that fuel line is not kinked, twisted or bent. If you do have fuel flow, turn the vehicle's ignition off and properly secure the fuel line to the nitrous injector.

Now open the release valve on the nitrous tank check for frost along the nitrous feed line. The frost will indicate a nitrous leak. If you find any leaks, close the release valve on the nitrous tank and cure the leaks. Open the release valve again and ensure that you've cured all nitrous leaks. Then disconnect the nitrous line from the nitrous injector. Activate the system and check for liquid nitrous flow when the system is activated, and that the nitrous stops flowing when you deactivate the system. If you don't get nitrous flow, check that the nitrous solenoid is operating properly; and ensure that nitrous line is not kinked, twisted or bent. If you do have nitrous flow, you can properly secure the nitrous line to the nitrous injector.


Nitrous tuning is another simple procedure but you should first tune your engine without nitrous as you will be running without nitrous for most of the time. Tuning the nitrous system is quite straight forward — you start with the jet sizes recommended by the manufacturer of your nitrous system and gradually adjust the jet sizes until the air/fuel mixture added by the nitrous system is perfect.

So install the jet sizes recommended by the manufacturer of your nitrous system. This will be conservative and will err on the rich size (i.e., too much fuel), which is the safe side to err on. Run you engine for a while with the nitrous activated and then check each of your spark plugs to determine how the air/fuel mixture is burning. The correct air/fuel mixture will produce a brownish, grayish-tan color on the spark plugs. If the spark plugs have a sooty, black color, your air/fuel mixture is too rich and you should increase the nitrous jet to the next jet size. If the metal part of the spark plugs displays a bluish or rainbow coloration, go to a smaller nitrous jet size immediately. Repeat this test until your spark plugs display the correct color. Never jump up by more than one jet size on the nitrous side and never try to work your way down from a lean mixture — that's just looking for trouble and major engine damage. You can make more power by increasing the fuel jet size and then adjusting the nitrous jet size up until your spark plugs display the correct color again.

WARNING: Back off as soon as you get detonation and reduce the size of your nitrous jet!

You may also need to adjust your ignition timing as nitrous oxide makes the air/fuel mixture burn much faster than normal. Retard the ignition timing by 2° increments (i.e., less advance before TDC) until you feel a noticeable loss of power. Then advance the ignition timing by 2°.

Now that that's done, your nitrous system is installed, tested and tuned; all that's left is for you to enjoy responsibly — always enjoy power responsibly!

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