2001 Pontiac Trans Am Intake Manifold Nitrous Install - F.A.S.T. On The Gas

Although this Firebird is not currently equipped with an adjustable fuel-pressure regulator, we still thought it would be a good idea to install a fuel-pressure gauge to keep tabs on things. ZEX's jetting is set up assuming 58 psi of fuel pressure, and this mechanical Auto Meter gauge showed us just that, ensuring that we wouldn't have to worry about an incorrect nitrous-to-fuel ratio. Carrying PN 2177, Auto Meter's suggested retail for this gauge is $38.

The red 3AN hoses run from the tee at the outlet of the fuel solenoid to the fuel distribution blocks (with some difficulty under the cramped cowl, thank you very much), and the purple hoses from the nitrous solenoid to the nitrous distribution blocks. One may have to get creative in the routing of these lines to not only reach the distribution blocks, but also get them there at the correct angle. ZEX uses a "dual-stage" jet system in which both the distribution blocks and nozzles have jets. A 40 nitrous jet and a 21-fuel jet were used at their respective distribution blocks. Swapping these allows fine-tuning the nitrous/fuel mixture without having to change every single nozzle jet.

We also installed the ZEX Nitrous Purge Kit, which was part of its Racer's Tuning Kit (also available separately). The purge kit includes a separate solenoid that serves to purge nitrous vapor from just upstream of the nitrous solenoid, ensuring liquid nitrous is available to the nozzles as soon as the system kicks in. We routed the purge line to shoot a sweet plume above the car's hood. The Racer's Tuning Kit (PN 82001, $332) also includes a bottle warmer, bottle-pressure gauge, and a safely blow-down kit.

Nitrous oxide kits by nature involve a lot of wiring, and this kit was no exception. An excellent feature of the ZEX system is its use of an electronic throttle activation switch. Using a signal from the TPS, it won't allow the nitrous and fuel solenoids to open below full throttle (or very close to it). Its one-touch push-button programming learns the TPS curve and makes setup a snap; just press the button atop the unit, hold the throttle wide open for 10 seconds, and that's it.

In order to determine the proper wire from the TPS that gives an output voltage to the engine computer, a voltmeter is used. With the car's ignition on, stab the positive lead of the voltmeter into each wire while opening and closing the throttle. The correct wire will give you a changing voltage as you open and close the throttle.

On this car, the TPS output voltage wire was dark blue. Just tap into it a little upstream in the wiring harness and connect it to the white wire running from the ZEX electronic throttle activation switch. A spade-type tap works best since it can be easily disconnected from the white wire if you ever have to reroute wiring.

The red wire from the electronic throttle activation switch runs inside the vehicle to a system arming switch. The black wire goes to ground, and the blue wires go to the relay seen here. Two of the wires from the relay go to the battery and are fused for protection, and the final wire coming from the relay is the power source for the nitrous and fuel solenoids (we used a red wire for it, too). At full throttle, the electronic throttle activation switch gives a signal to the relay to "close" (complete) the circuit from the battery to the solenoids, thereby opening the solenoids and sending nitrous and fuel into the engine.

But, not so fast, ZEX. We want an extra level of protection on our vehicle. Not only should nitrous oxide be used only at full throttle, but it also should not be used below 2500 rpm, lest cylinder pressures go through the roof. Therefore, instead of connecting the other leads from the solenoids to ground, we wired them into MSD's new Digital RPM Activated Window Switch, PN 8969 (suggested retail $150). This switch will only connect the solenoids to ground during a preprogrammed window of engine rpm.

MSD's digital window switch easily hooks up to just about any vehicle you can imagine and is so easy to program, your electronics-incompetent dad could do it. Just specify the rpm for the circuit to close (we chose 3000) and the off rpm for the circuit to open. This latter setting should be about 100 rpm before the engine rev limiter kicks in since it's a bad idea to be spraying nitrous while the engine is bumping off the rev limiter.

The MSD switch needs an engine rpm signal to operate, and this is easily had. On '99-and-later LS1 F-bodies, the ECU tach output is pin 10 on the computer, a white wire. Also note that for LS1 vehicles, the switch must be set to four-cylinder mode, thanks to the nature of the LS1's tach signal. In eight-cylinder mode, the switch will interpret the engine as running at only half the rpm it actually is.

Since several of the wires from underhood need to get inside the driver's compartment, it's necessary to make a hole in the firewall. The only practical way of doing this is to set up a hole saw on a massive extension so that the firewall can be reached. We found that the flat spot just above and to the passenger side of the throttle cable entry area provided easy access from both sides of the firewall without obstructing anything.

It's essential that one is able to monitor nitrous pressure from inside the vehicle, and an electric pressure gauge from Auto Meter is a darn good choice. This Phantom unit, PN 5774, measures 2 1/16 inches in diameter and retails for $276. Its use of an electric sending unit means that there are no nitrous lines to run into the interior of the vehicle.

The 1/8 NPT Auto Meter nitrous pressure-sending unit can tap into a nitrous line anywhere upstream of the nitrous solenoid. We bought a tee at Sears in order to tap into the gauge adapter that came with ZEX's underhood nitrous pressure gauge, which we had mounted directly to the inlet of the nitrous solenoid. Helpful ZEX hint: red Loctite can be used in lieu of Teflon paste if an NPT fitting won't seal; sometimes the paste can be pushed out of the fitting under the high pressures of nitrous oxide.

In order to route the 4AN nitrous delivery line to the bottle at the rear of the car, we chose to go through the passenger-side fenderwell. A factory gap just next to the battery is an excellent access point to get in from under the hood. Snaking the line through the area pictured is made much easier if one removes the front wheel and some of the bolts holding the plastic fender liner in place.

For us, the ultimate destination of the nitrous delivery line was the spare tire compartment. To get there, the nitrous line must be securely attached to the underbody of the car up and out of the way (and preferably not visible from outside the car). It's a good idea to drill holes every foot or two and zip-tie the line in place.

Included as part of ZEX's Racer's Tuning Kit, the safety blow-down kit is required for all cars that do not have separate trunks. One piece of this kit is a new fitting for the nitrous bottle that allows a blow-down tube to screw onto it. Like the one it replaces, the fitting has a metal disc inside that will rupture at 3,000 psi, sending 10 pounds of expensive nitrous into the atmosphere. This will only happen if the nitrous bottle is dangerously overheated (we're talking hundreds of degrees here) or is hit in an accident, and is way better than the bottle itself rupturing.

A nitrous bottle heater also comes with the ZEX Racer's Tuning Kit, and needs a source of power from the battery to work. This involves running a wire through the interior of the car, which is only a slight pain in the behind. When switched on, the warmer keeps the bottle within a narrow temperature range in order to keep nitrous pressure at its optimum (around 950 psi). We really liked the built-in thermostats; unlike the ones on some other manufacturers' warmers, which hang loose and must be slapped to the outside of the bottle, ZEX's actually worked.

Though we no longer have a spare tire, we do have AAA, and they have flatbeds. No way were we about to lose storage space for the T-tops. ZEX supplies bottle brackets to hold the bottle securely in place. We custom-bent them a bit to hold the bottle to the side of the compartment rather than the floor, which is uneven and difficult to bolt anything to. If you do this, be sure to choose areas of the metal that are thick because most of it is rather flimsy. The horizontal area under the jack is pretty thick, and we made a 90-degree bend in one end of the forward bracket so that it could be bolted to it.