Richard Holdener
December 18, 2006
Replacing the conventional mechanical full throttle switch was wiring to the TPS sensor. The fuel con-troller will actually learn your TPS voltage curve to allow nitrous activation only under full throttle.

This change in nitrous flow (from heat and use) can alter the power supplied, to say nothing of the air/fuel ratio. The trick Active Fuel Controller adjusts for this change in bottle pressure to help optimize power production. In addition to the regulatory duties, the Active Fuel Controller featured a patented electronic TPS switch. The controller actually has the ability to learn the TPS voltage curve of your motor and will only activate once the maximum (acceptable) TPS voltage is reached. This ensures the nitrous will never be activated at part throttle. Too little throttle angle or engine speed can create a backfire situation-definitely something to be avoided with the factory composite intake manifold.

According to Zex, its EFI Wet System also features a unique fogger-nozzle design. Like other systems, the fogger nozzle was designed to combine both fuel and nitrous into the motor, but the Zex fogger has a pair of important features to further improve both atomization and safety. The first advantage offered by the unique fogger was Fuel Shear technology. The fogger nozzle featured a transfer tube to directly inject fuel into the highest velocity area of the nitrous plume. The high-speed nitrous gas shears the fuel away from the transfer tube, thereby maximizing the atomization. The greater the atomization, the better the fuel distribution among cylinders. This was ultra-critical when injecting the nitrous/fuel combination into the long-runner EFI intake on our '96 GT. In addition to Fuel Shear, the nozzle also features Active Fuel Control. The design of the fogger nozzle creates a vacuum across the top of the fuel transfer tube. As the speed of the nitrous flow changes (from changes in bottle pressure), the vacuum created also changes. This change in vacuum across the fuel transfer tube increases or decreases fuel enrichment to further optimize safety and performance.

Installation of the Zex kit was fairly straightforward, including mounting the bottle in the trunk (make sure you don't drill a hole in the spare tire-we speak from experience here), drilling and tapping the air inlet tube for the fogger nozzle, and mounting the fuel controller in the engine compartment. The Zex kit included the necessary fitting to replace the factory Schrader valve to act as a fuel supply to the fuel controller. With the fuel and nitrous feed lines connected to the controller, all we had to do was run the pair of nitrous and fuel lines from the controller to the fogger nozzle.

We made sure to insert the 46 nitrous jet and 30 fuel jet to supply our desired 100hp nitrous shot-a safe level running 91-octane pump gas. The arming switch (to activate the system) was located inside the car (hidden away in the unused ashtray), while the activation switch was actually the TPS switch in the fuel controller. We chose a momentary activation switch as it was possible to activate the nitrous at low engine speeds (since activation only required the arming switch and full throttle). We like running full throttle at lower engine speeds than 3,500 rpm-a safe activation rpm for nitrous-so we decided to activate the nitrous manually with a momentary switch. The TPS switch in the fuel controller made sure activation could happen only at full throttle, but we were free to manually select the activation rpm.

Before testing, it was necessary to go through a learning sequence for the active fuel controller, to allow the system to learn the TPS voltage curve. This required turning on the ignition key (but not starting the motor) and then turning on the fuel controller. We then pushed down the gas pedal to full throttle and held it there for 10 seconds to allow the controller to learn the full-throttle voltage supplied by our TPS. After that, a quick check revealed all systems were go.

This button was used to initiate the learning mode on the controller. After switching everything on, we simply pushed down the throttle for 10 seconds, and the controller recognized the full throttle voltage of our system.

Before heading to Westech for testing, we took the liberty of requesting a switch chip from Steve Ridout at Powertrain Dynamics. He set us up with a dual-position chip that allowed us to run two programs. Program 1 was the standard program, while program 2 retarded the total timing by 3 degrees in anticipation of the nitrous. The instructions supplied by Zex recommended retarding the timing by 3 degrees at this power level (on pump gas), so we heeded this advice.

Run in baseline trim (no nitrous), the 4.6 produced peak numbers of 274 rwhp at 5,200 rpm and 316 lb-ft of torque at 4,200 rpm. Activating the Zex nitrous kit bumped those figures to 377 hp and 497 lb-ft of torque. The gains offered by the 100hp shot were great at 131 hp and 182 lb-ft.

We can't wait to see how it feels on the street against some unsuspecting Camaro.