Adding nitrous to the already potent Nissan Skyline GT-R may seem like overkill to many. Where we come from if there is a way you can make more power you take it. Our test subject has an enviable racing history. It was modified for Pike's Peak competition and was the Showroom Class winner in 1999. After Pike's Peak, Sean Morris of MotoRex had the motor "tweaked" to where it was putting out around 444 horsepower at the rear wheels. He intends to have this car set up to compete in import drag racing. We decided to follow the installation of a Nitrous Oxide Systems kit on this car to better illustrate the installation steps touched on in the preceding Basic Tech article.
The installation was performed at the So-Cal Speed Shop in Pomona, Calif., builders of world-famous street rods, custom cars, strip cars, track cars, lakes cars and custom engines.
The NOS Sportsman Fogger' kit, P/N 05040-FINOS, contains all the hardware necessary for an inline fuel injected, six cylinder engine. It's a wet-manifold system, meaning that it injects both fuel and nitrous through its nozzles. Included are all hoses, lines, nozzles, distribution blocks, solenoids, filters, connectors and switches that are necessary for installation. The NOS Sportsman Fogger' kit comes standard with a 10 lb. nitrous bottle. This standard bottle was used in the installation. Kits can, however, be ordered with either a 15 lb. or a 20 lb. nitrous bottle. These larger bottle sizes can be specified by adding a suffix to the part number, "-15NOS" or "-20NOS", for 15 lb. or 20 lb., respectively.
1. To begin, the location and orientation of the NOS nitrous bottle had to be determined. It was decided that the trunk would provide the best location, but the bottle had to be mounted so that the siphon tube would be at the back of the bottle. This is necessary because the liquid N2O will be forced to the back of the bottle during vehicle acceleration. When installed, the bottle should have its valve handle pointed toward the front of the vehicle, with the NOS bottle label facing up. The bottle bracket was secured using 5/16" or No. 12 sheetmetal screws.
2. Next, the main nitrous feed line was installed from the trunk to the engine bay. It's easiest to route this line following either the main fuel line or the brake lines under the vehicle. One-half inch Tinnerman clamps or nylon tie-wraps could be used to securely support the nitrous line. A hole must be drilled through the trunk, under the vehicle, to gain access to the nitrous bottle. At this point, it's a good idea to disconnect the Negative ground terminal from the battery to avoid any unpleasant surprises.
3. Prior to removing the intake manifold for installation of the Fogger' nozzles, mark on the manifold the desired nozzle locations. These should be located approximately one inch (1") from the cylinder head. Make sure that there is adequate clearance for the Fogger(tm) nozzles, lines, fittings and distribution block. Remove the intake manifold and retain all hardware for re-installation. Remember to use NEW gaskets when re-installing. Take precautions such as covering the intake ports to prevent any debris from entering the engine. Refer to the manufacturer's service manual for sequence and torque specs of manifold bolts.
4. Once more, measure and verify the intake manifold location where you intend to install each Fogger' nozzle. All holes drilled should be perpendicular to their respective intake runner. Carefully drill a 1/4-inch diameter hole for each nozzle. If possible, drill the holes so that they all line up straight on the manifold.
5. Use a 1/16-inch NPT tap (available under NOS P/N 15990NOS) on each hole. Because this is a pipe thread, be careful not to run the tap too deep into the manifold runner hole as this may prevent the nozzles from adequately sealing. The goal here is to have the discharge orifice of the Fogger nozzle in the airstream within the runner to assure that the nitrous is being properly distributed. After the drilling and tapping has been completed, clean the manifold thoroughly and remove all shavings and debris.
6. Apply Teflon paste (do not use Teflon tape) to the Fogger nozzle threads before installing the nozzles in the manifold. This is to avoid the possibility of any vacuum leaks from occurring. Teflon tape should not be used because it requires relatively more torque to properly seal. This could cause damage to the NOS fittings and nozzles. The tape could also break loose and become lodged in the nitrous or fuel solenoids, or solenoid filters which can cause engine damage or failure.
7. Install a NOS Fogger' nozzle into each of the manifold runner holes. Orient them so that each discharge orifice is pointed down the intake manifold port, toward the cylinder head intake valve. The discharge nozzle orifice needs to clear the roof of the intake runner by about 1/8 inches. Be careful not to over-torque the nozzles.
8. Now is the time for bending the hard lines to connect the Fogger nozzles to their respective distribution blocks. A tube-bending tool, available under NOS P/N 15991NOS, is required for this work. Use all the fittings provided and be aware that NOS has color-coded the nitrous lines so that "red" is for fuel and "blue" represents nitrous. Nitrous nozzle feed lines should be bent and plumbed so that they are in line with each distribution block.
9. Re-install the intake manifold, using all hardware that was retained during its removal. Be sure to use a new intake manifold gasket. Re-attach all lines, electronics and any other parts that were removed or disconnected during the intake manifold removal process.
10. The next step is to tap into the fuse box for an ignition-activated power source for the toggle switch that is used to "arm" the nitrous system. This switch can be installed at a location on the dash that is convenient to the driver. Activating this switch puts the nitrous system into a "standby" mode. The system itself won't actually function until the engine is at wide-open throttle (WOT). This condition is confirmed by a WOT micro-switch that is installed on the throttle body.
11. The purge valve (a momentary button) can be installed at this time. This valve is activated to expel or purge the nitrous lines prior to use for more consistent performance. This procedure is good insurance that the nitrous lines are free of air and/or gaseous nitrous that could hinder or compromise performance. Be sure that the purge line is aimed away from the motor. A good idea is to have the purge line aimed so that it will shoot up and over the windshield.
12. The last installation step is to plumb an additional source of fuel to the fuel solenoid. Fortunately, the Skyline had an extra NPT tap on the O.E. fuel rail; this was used as a fuel source.