We removed the stainless steel...
We removed the stainless steel oil line that feeds the turbocharger's bearing housing and placed it in a suitable container. Although we flushed out the line with isopropyl alcohol after installing it on the oil-pressure block-off plate, it's cheap insurance to make sure the line is free of any debris and that the turbo will have instant lubrication upon startup. We connected the battery, started the vehicle, and let it idle. After oil started flowing cleanly, we turned off the key and reinstalled the oil line. We then disconnected the rubber STS oil hose from the oil fill cap and put the hose into the same container. Then we started the vehicle and let it idle until oil pumped into the container. With those tasks done, we connected the oil hose to the oil fill cap, satisfied that the oil pump was operating properly.
Before finishing the install,...
Before finishing the install, Mike DuSold of DuSold Designs prepared the Y-pipe and the junction where the turbocharger mounts to the intermediate pipe to be welded. After roughing up the metal surface, he expertly welded the junctions with a MIG welder to ensure a leak-free system.
The installation team consisted...
The installation team consisted of Billy May (right) and Dustin Burris of Texas Rear Turbos, and Allen Nelson (left) of Nelson Performance (not pictured are the expert technicians of Real Performance Motorsports and DuSold Designs). They topped off the oil and checked everything once more before starting the Pontiac and looking for exhaust and/or oil leaks. Installation of a custom tune and testing followed, where it was determined that a lack of fuel was causing the Firebird to lean out at WOT (see Testing: On The Street sidebar).
"Upon returning to the shop and discussing the setup with Billy, we decided that a fuel-system upgrade was necessary. In order to make the car safer until upgrades were performed, I revised the tune to allow only 4 degrees of timing at wide-open throttle and told the owner not to take the car over 4,000 rpm. For comparison purposes, the factory tune on a stock vehicle is set between 26 and 28 degrees, and my target for the STS-equipped Firebirds is 16 degrees.
"After discussing the test data with Rick Squires of STS and the owner, Rick asked that the owner provide some scan readings by using their Autotap software. Even with only 4 degrees of WOT timing, the car was leaning out above 3,500 rpm and showing A/F ratios upward of 13.5:1. In both testing scenarios, the small 26.4-pound injectors were showing that they were being severely overloaded. A good rule of thumb is that the injectors shouldn't be pushed beyond 80 percent duty cycle, and this car was running over 115 percent duty cycle. Bottom line, the fuel injectors couldn't supply enough fuel to the engine at WOT.
"After doing the calculations, we determined that at a minimum, the car would require a set of 37-pound injectors. Since the cost and tuning ability of the Delphi 37- or 42-pound injectors are a push, we chose to provide a bit of margin and selected the 42-pounders (flow 48.8 pounds at 58 psi versus the 37-pound injectors that flow 43 at 58 psi). After installing the 42-pound injectors and a custom tune, I was able to meet my goal of an 11.8:1 A/F ratio at WOT.
"It would have been very helpful to have the Auto Meter gauges installed before the retune, but they weren't available then. The Formula started to lean to around 12.5:1 above 4,500 rpm, but I was able to adjust the fuel-injector pulse widths to maintain the safe target. No knock retard was noted after the final tune, and the inlet air temperatures (IAT) were very reasonable given that the testing occurred at an ambient temp of 90 degrees. With the 5-psi boost level, I logged a maximum IAT of 150 degrees, with only 118 degrees noted with the methanol injection flowing.
"Since only one PCM tune can be installed in the car, the system was optimized for the base 5-psi kit. When the electronic boost controller was flipped and the car ran 7.5 psi of boost, the Formula ran a bit richer at 11:1. After Texas Rear Turbos installed the fuel pressure and boost gauges, the fuel pressure was observed falling off to 42 psi while under boost. Additional monitoring showed that the car was still operating safely, but any degradation in the fuel system operation would be dangerous.
"In order to correct the fuel pressure and volume deficiencies, additional fuel-system upgrades and monitoring are necessary to make sure the car operates safely. My recommendation is that the Formula be upgraded with an aftermarket high-volume fuel pump. Once this is complete, I can revise the tune to match the upgraded fuel delivery and would strongly suggest that a wide-band O2 gauge be installed to monitor the A/F ratio at all times."
Testing: On The Dyno
In stock configuration-other than a skip shift eliminator and Exedy twin-disc clutch with flywheel-the Formula put down 308.2 hp and 318.2 lb-ft of torque. According to Wade Wells, technical assistant at RPM, "The Formula produced good power numbers considering it registered an average A/F ratio of 11.8:1. The vast majority of stock F-bodies run leaner air/fuel ratios of 12.8 to 13.0:1."
For the dyno session with the STS turbo system installed and a Nelson Performance custom tune, the 5-psi boost setting put out 392.6 hp, or an 84.4hp increase over stock. Torque followed right along, registering 401.7 lb-ft, an 83.5 increase. The air/fuel ratio registered at 11.7:1 on average-perfect for a boosted application.