More than 13 years ago, Pontiac began rolling Trans Ams off the Sainte-Thérèse assembly line with the new LS1 engine under the hood. This sophisticated powerplant would further the perception of the Trans Am as a top-notch performer that provided great value. Over the past 13 years, we’ve seen the prices on these cars fall from $30,000 new to $20,000, $10,000, and now they’re even cheaper in various conditions, making them a phenomenal performance/dollar value. We decided to apply the same formula to a ’99 T/A with a new plate nitrous system from Zex, and Chris “Whistler” Kirchner helped out on the install and testing.
We explained to Zex that we plan to grow into the nitrous kit. Trent Goodwin at Comp Cams, Zex’s parent company, told us that the new LS Series Perimeter Plate Nitrous System for cable-actuated throttle bodies (PN 82391) would be just the ticket. It’s adjustable from 100 hp all the way to 250 hp, and since we don’t plan on spraying anything less than 100 hp, it’s a perfect choice for us so we can step up to higher levels later on.
The kit was designed with the large 90mm four-bolt intakes in mind, as well as the FAST LSXR 102mm. Our Trans Am came equipped with some aftermarket goodies, including the old-style FAST 90mm intake—FAST has since moved on to the 102mm.
This is the new Zex LS Series...
This is the new Zex LS Series Perimeter Plate Nitrous System for cable-actuated throttle bodies (#82391). The kit comes with everything you need to hook up to an LS-engine using a 90mm or larger throttle body, but it is not car-model specific. As we found, you may need a few pieces to custom fit it to your Bird. In addition to common hand tools, you will need a good wire cutter/stripper, assorted AN lines if you want to alter the solenoid mounting location, and a pack of assorted electrical connectors.
The plate uses 12 injection points around the perimeter of the intake manifold’s inlet to create what Zex calls, “a perfectly atomized blend of fuel and nitrous.” It’s also part of Zex’s Blackout series, which uses black nitrous lines and a black bottle for a stealthy, cool look. The kit comes with everything needed to install it, but depending on how you would like to personalize it, you may need to have a few parts on hand. We required a 90-degree elbow fitting, an 18-inch nitrous line, and assorted electrical connectors.
In order to install this kit in what we felt was a professional and clean manner, we opted to make a custom bracket for the nitrous and fuel solenoids, and wide-open-throttle switch. Because of this, the install took longer than anticipated. Figure on setting aside a full day for the install, but know that it can be done quicker. If you want something more plug-and-play, look into one of Zex’s kits made specifically for your Pontiac model.
After about 12 hours (including taking photos), we had our customized kit installed and ready to go. In Part I, we cover the installation of the parts and plumbing. For the second installment, we will wire the system, and discuss the nitrous and fuel pills and how they correlate to a power increase. Additionally, we’ll get some dyno numbers and track times. So stay tuned!
Part Numbers And Prices |
| Parts |
Price |
Part Number |
| LS Series Perimeter Plate Nitrous System (Cable) |
$750 |
82391 |
| Big Mouth 102mm Throttle Body |
$510 |
54102 |
This is what all the excitement...
This is what all the excitement is about—the new nitrous perimeter plate. Zex claims that it creates a superior blend of nitrous and fuel over traditional kits. Older Zex kits can be converted to the plate system.
If you’re running an older...
If you’re running an older 90mm FAST intake or a new FAST 92mm throttle body, you’ll need to use the supplied adaptor ring and rubber seal, seen in place in the previous photo.
The 102mm Big Mouth throttle...
The 102mm Big Mouth throttle body is very large. To avoid any possibility of incompatibility, we ordered and installed it because it’s known to work with the system without issue.
With the battery disconnected...
With the battery disconnected and after removing the air box and MAF assembly, throttle cable, and throttle body, we installed the plate and the new throttle body on the FAST intake using the supplied gaskets and a 10mm wrench and socket. Then we reinstalled the air box and MAF and hooked up the throttle cable. We can now decide where to mount the solenoids and begin plumbing the lines and wiring.
Seeking a more custom look...
Seeking a more custom look for the install than the generic, supplied brackets would provide, Chris made a simple 90-degree bracket that would mount directly to the passenger-side cylinder head by employing two unused bolt holes. Using a piece of 6x10-inch scrap diamond plate, Chris simply bent it in a vice to make a crisp line. We bought a longer nitrous line (approximately 18 inches) because mounting the solenoids where we did meant the supplied 12-inch line wouldn’t reach.
We positioned the solenoids...
We positioned the solenoids on the bracket and outlined them. Then we removed the bracket from the car and made this stencil of the bottom so we could correctly drill the solenoid mounting holes.
Another advantage to the new...
Another advantage to the new bracket was that it gave us a terrific mounting point for the supplied wide-open-throttle switch. It’s wired directly to the solenoids and a power line is brought into the back. This switch completes the circuit when the throttle blade is fully open and allows the nitrous and fuel solenoids to activate.
Again, Chris outlined the...
Again, Chris outlined the supplied bracket that we modified (bent) to fit our custom setup and drilled the holes—this time to properly mount the wide-open-throttle switch.
Here’s our complete custom...
Here’s our complete custom bracket setup. “The best part about this mounting style is that it makes the assembly very easy to remove and work on,” says Chris.