Nissan 350Z Project Vehicle Nitrous Installation

We purchased a new 2006 Nissan 350Z as a project vehicle for developing our NC-1 and NC-2 nitrous controllers. In this part of the Tech FAQ, you can see a good example of a professional nitrous system installation.

 

2006 Nissan 350Z Project Vehicle

 

Before we started installing and testing the nitrous system, we modified the exhaust and installed a Nismo limited slip differential. The exhaust modification involved literally cutting off the stock muffler and replacing it with a custom fabricated Y pipe with new tips. This approach can be used on many catalytic converter equipped vehicles, as the catalytic converters significantly quiet the engine. The 350Z came with a small resonator (at the bottom of the picture) that was left intact. The overall sound is aggressive, but not loud enough for any legal hassles. This custom exhaust is certain to have less restriction than any of the available aftermarket systems and weighs a lot less too - not to mention the cost savings. 

The Nissan 350Zs come with a viscous slip differential that is great for wet and slippery conditions, but totally useless for preventing wheel spin at wide open throttle. We installed a Nismo limited slip differential (LSD). The Nismo LSD is a fairly hardcore part. It can be set for three levels of breakaway torque. The medium setting gave good traction results but also lots of chattering in low speed corners. We changed the gear oil to Red Line 75W90 gear oil (not the 75W90NS) and added Red Line limited slip friction modifier additive (two 4 oz bottles). We were able to "tune" the properties of the LSD with the friction modifier additive to eliminate all the low speed chattering. 

350Z Custom Exhaust

 

We chose a Nitrous Express P/N 20923-10 import EFI kit. This is a wet system where fuel and nitrous injection can be individually jetted. We began our nitrous system installation with the bottle. There are three important criteria for bottle installation: safety, convenience, and cosmetics. Safety is the top priority. The bottle mount must be secure. In the event of a frontal collision, you do not want to have a 25 lb projectile coming at you. In the 350Z, the only good location that meets all three criteria is to mount the bottle in place of the spare tire in the rear compartment. The first picture shows the finished installation with the carpeted cover in place over the bottle - only a slight hump is visible. The second picture shows the plastic tire cover cut out for bottle clearance. The third picture shows the 1/4" aluminum plate that was fabricated to serve as a bottle mount. You can see the bottle heater and pressure switch (ARC P/N AN-719DWK-4 dual voltage 12 VDC and 120 VAC) and bottle solenoid valve (Ny-Trex P/N 20095). You can also see nitrous feed line and added electrical harness that exits the rear compartment via an existing rubber grommet at the upper right corner. The aluminum mounting plate was secured to the existing spare tire mount. This required a round cutout to clear the tire mount. A 3/4" phenolic spacer and aluminum disk are used to attach the mounting plate to the tire mount.  The grey PVC tube shown in the picture serves as a support for the plastic tire cover. We also installed an aluminum L bracket that helps retain the front of the mounting plate using two existing screws. The entire assembly is robust enough to survive a crash. The last picture in the series shows a detail of the heater, bottle solenoid valve, pressure switch, and associated relays. When the bottle is removed for refilling, the heater, solenoid valve, and pressure switch remain attached. Two Weather Pack connectors are used to allow disconnecting these accessories from the vehicle wiring.   

350Z Nitrous Bottle Installation with Carpeted Cover In Place

 

350Z Nitrous Bottle Installation Showing Cutout in Plastic Tire Cover

 

350Z Nitrous Bottle Installation 

 

350Z Nitrous Bottle Installation Detail

 

The next step was to install the engine compartment components. Fuel is taken from the main fuel rail using a Courtesy Nissan P/N CN-001 fuel line T adapter. To avoid a momentary lean surge, any fuel pressure drop when the fuel solenoid is activated is reduced by a Nitrous Express P/N SPEED00010 fuel accumulator. The system also includes a Wilburn Motor Sports Pressure Pro nitrous pressure regulator set at 900 psi, Nitrous Express P/N 15600 purge valve and P/N 15603 nitrous pressure gauge (mounted at the outlet of the nitrous pressure regulator). A normally open fuel pressure switch (Harris Speed Works P/N HSW-ELC-FPSSE-4AN) senses fuel pressure downstream of the fuel solenoid. An aluminum bracket was fabricated to hold the solenoid valves. The bracket is mounted to existing screw holes. All the major components are readily accessible. While this  arrangement resulted in a very clean looking installation, it did require extra long nitrous and fuel lines. The entire under hood installation only required drilling two holes: one in the firewall to secure the fuel accumulator and another in the cold air intake for the nozzle. 

350Z Nitrous Installation

 

350Z Fuel Tap and Fuel Accumulator

 

 

350Z Nitrous and Fuel Solenoids

 

350Z Nitrous Nozzle Detail

 

The final step was to install the NC-2 nitrous controller and switches. The NC-2 controller was installed on a phenolic plate (for extra support) mounted to the passenger side kick panel. Two rocker switches with status LEDs are used to control system operation. These were mounted on an unused accessory panel on the center console. 

350Z Nitrous Controller Installation

 

350Z Nitrous System Switches

 

The NC-2 progressive nitrous controller triggers the nitrous system based on RPM, throttle position, and vehicle speed. Stage 1 is used for the fuel solenoid and stage 2 for the nitrous solenoid. A normally open fuel pressure switch senses fuel pressure downstream of the fuel solenoid. The switch is set to close at 35 psi. When the fuel solenoid is activated and pressure builds up (indicating actual fuel flow), the fuel pressure switch activates Stage 2 (the nitrous solenoid) by means of the GPIO input on the NC-2 controller. Progressive control is used on the nitrous solenoid, ramping up from 25% to 100% flow between 3750 and 5250 RPM. This gives reasonable air/fuel ratio values throughout the nitrous system operating range from 3000 to 6750 RPM.

The system is controlled by two console mounted rocker switches with LEDs. The arming switch arms the NC-2 controller and opens the bottle solenoid valve. When the NC-2 controller is armed, it initiates a 2 second auto-purge. The status LED in the arming switch indicates NC-2 controller status (illuminated when the system is armed and flashing if an error occurs). The bottle heater switch turns on the ARC bottle heater system. The bottle heater is controlled by a pressure switch that opens at 900 psi and turns the 12V heating element off. The status LED in the bottle heater switch is illuminated when the heater is on. When the LED is off (switch must be in on position), the bottle has reached normal operating temperature (about 85 deg F or 900 psi).

 

 

 

The combination of the pressure controlled bottle heater and nitrous pressure regulator allows a constant nitrous pressure to be maintained under all operating conditions. The bottle heater also has a 120 VAC element. This heating element is not controlled by the pressure switch and is only used to preheat the bottle during cold weather. One other important note relates to safety of the bottle heater system. The pressure switch is attached to a fitting on the bottle valve that remains pressurized even if the valve is closed. Otherwise, the pressure switch would not shut off the heater element if the heater system was turned on while the valve was closed and pressure in the bottle could rise to a dangerous level.    

After some dyno tuning, using our WEGO system to check air/fuel ratio values, the nitrous system was setup with a #25 fuel jet and a #57 nitrous jet. The only other engine modification was to install cooler NGK LFR6A-11 spark plugs to reduce the possibility of pre-ignition. These are V-grooved copper electrode spark plugs that will require replacement about every 10000 miles.

Baseline dyno test results (no engine mods) were 242 HP at 6600 RPM and 212 ft-lbs torque at 5000 RPM. These are about the expected values for a stock 350Z. With the nitrous system activated, dyno test results were 330 HP at 6300 RPM and 310 ft-lbs torque at 4800 RPM.

350Z Dyno Test with Nitrous System Activated