1998-2002 Pontiac Firebird - STS Subterranean Turbo System Installation - Part 2

Once completed, position pipe No. 4 and, beginning with the rear control arm, insert the 18mm bolt and nut through the STS pipe, but do not fully tighten. Thread the two supplied 16mm bolts with lock and flat washers through the bracket and snug them up with a socket wrench.

Position the pipe so that the front bolts can be threaded in, and snug up the bolts. Put a 211/44-inch silicone hose onto each end of the pipe. Note that this photo is taken from the front of the vehicle to the rear and shows just how close the air intake piping comes to the driver-side bend in the factory Y-pipe. In our opinion, a heat shield integrated into the forward bracket to reduce the amount of heat transferred to the piping would be a great addition.

After securing the front bracket, slip pipe Nos. 3 and 4 together, along with the two hose clamps that are used on each hose, and position pipe No. 3 to allow for maximum ground clearance. Once you have the pipes positioned, do a final tightening of pipe No. 4 and then secure the hose clamps. Make sure the junctions and hose clamps are secure, as under boost the last thing that you want is for the pipe to blow off or leak, either eliminating or significantly decreasing performance.

Before mounting the rest of the piping that will connect to the throttle body and pipe No. 5, install the Tial 50mm blow-off valve to pipe No. 6. Slip the O-ring in the pipe. A steel flange secures the valve. The BOV is designed to dump boost in the pipe, by relying on engine vacuum to suck the BOV open when it senses approximately 22 inches of vaccum or roughly 11 psi. Pressure relief is modulated via an internal spring.

"T" the blow-off valve into the brake booster line and connect a rubber line from the center of the T to the banjo fitting on the blow-off valve.

Before connecting the piping that mates the MAF assembly to the throttle body, swap out the factory spark plugs with a fresh set of NGK TR-6 plugs. Since spark knock is the enemy of a boosted application, the NGK plugs are two full heat ranges cooler. The plugs were gapped at 0.030 inch with a Jacobs Electronics gapping tool. STS recommends a plug gap of 0.035 without methanol and 0.030 with methanoldue to the latter's higher boost potential. If you experience misfire with your non-methanol-equipped system, decrease plug gap to 0.030. Even a few thousandths wider plug gap can make a difference when operating with the very high cylinder pressures developed under boost. In most cases, the LS1-equipped Firebirds came with AC Delco plugs, but Denso plugs were the factory fill on this Formula. A light coating of antiseize compound on the threads will keep the plugs from seizing in the cylinder heads, assuring an easy change down the road.