The total installation took the better part of an afternoon to complete-about 5.5 hours-with basic tools and an above-average technician spinning the wrenches. This included the installation of the inline fuel pump that was supplied with the kit to ensure a steady head of liquefied lizards at the fuel rail. Luckily, our Caprice has a lot of space by the fuel tank area to make installation easy.
Because the Zex system has the solenoids, wiring, and other major connections all assembled and housed inside a purple-anodized management unit, installation is greatly simplified compared to other kits that we have installed. We simply mounted the management unit to the driver-side inner fender and began hooking up the system's uncomplicated connections. Two hoses go to the fuel pressure regulator's signal line and allow normal operation when the nitrous system is switched off. When the nitrous is armed and activated, a regulated amount of high-pressure nitrous oxide gas pressurizes the fuel pressure regulator's diaphragm and spikes the fuel pressure to about 85 psig, subsequently increasing the flow rate of the fuel injectors by about 50 percent. This is how additional fuel is added to each cylinder to complement the nitrous oxide.
On the other side of the management unit, we ran the braided stainless steel nozzle line to the nozzle itself that was mounted in the air tube just upstream of the throttle body. Zex recommends installing the nitrous nozzle as close to the throttle body as possible for enhanced response time, so we did as we were told. We then hooked up the 16-foot nitrous feed line to the back of the car and into the trunk area, where we mounted the 10-pound aluminum bottle with the supplied brackets.
Because the Zex management unit has a microprocessor built in that can detect WOT based on a five-volt signal from the TPS (throttle position sensor), there's no need to mount a traditional on-off microswitch on the throttle linkage. All we had to do was splice into the output signal wire coming out of the TPS as it goes into the PCM (Powertrain Control Module) and program the Zex controller to detect the WOT voltage point as the instructions explained.
While we were under the hood, we decided to pull out the stock spark plugs and install a fresh set of Zex units. These Power Tune spark plugs are designed for LT1 applications and performance use with or without nitrous oxide. When not subjected to the power adder's increased cylinder pressures, they also provide a cleaner, more efficient spark thanks to a tip design with multiple electrodes that transfers more spark energy across the gap and takes heat away more quickly. Pretty neat stuff.
Gettin' off like O.J.
With our Zex system installed and our drag radials mounted, we headed back to Old Bridge Township Raceway Park in New Jersey to see what kind of gain we'd be rewarded with on the dragstrip. The car was seriously strong on the street when armed with nitrous, and we knew that getting a good number wasn't going to be all that hard. On the line, we stalled up the converter a little (we have no tachometer to tell you exactly where, but it sounds like mmmmm) and flat-punched it with the nitrous system locked and loaded. Incredibly, the car torqued over and spun the tires, pointing the car toward the wall. We quickly aborted the run and decided to let the track get a little warmer before we hit it again. The anticipation was high, and we let the car cool down for another run.
On the next pass, we did a lengthy burnout, putting plenty of heat into the Nitto drag radials, which were inflated to 17 pounds. On the line, we again stalled up the converter, and once the green light dropped, we flat-punched the car and it shot off the line with a rather strong 1.78 short time. With the car running like a champ all the way down the track, we were wowed by the 13.522 at 98.70 mph that was printed on the timeslip in our hands. We improved our e.t. by almost nine tenths (0.883 seconds, to be exact) and picked up 5.89 mph from our previous best of 14.405 at 92.81 mph without nitrous. In the 60-foot time alone, we went from a 2.051 to a 1.780.