When we first saw the STS turbocharger mounted near the rear axle of a fourth-gen F-body, we had some hesitation. After all, turbos have always been located in the engine compartment where they can build up enough heat to cook a pizza while consuming precious under-hood real estate. But then one of the freethinkers from the office said, "Why not mount it in the rear?" and we scrambled for answers.
Just about that time, Rick Squires of STS Turbo Systems threw us the keys to one of his pressurized Firebirds equipped with one of his new patented turbo kits and told us to take it for a rip. We couldn't find an open stretch of industrial L.A. road quick enough and we couldn't believe the rush. Nail the throttle of an LS1 that inhales through one of STS's turbos and you'll feel like you're traveling at fast-forward-video speed down the asphalt. After we got back to the building and pulled our faces back into place, we had to learn more about these butt-mounted hair driers.
Squires always loved the sensational power a turbo produced, but didn't like the high-underhood heat, packaging restraints, and additional front-end weight a traditional turbo location brings with it. He decided to mock up a system that mounted the turbo under the car away from the engine heat. The solution was to install the blower where the muffler once lived and from there, plumb the intake tubing up to the engine to provide the boost, while the 38mm wastegate bleeds unneeded exhaust to control the boost pressure. The turbo would serve double-duty to muffle the exhaust sound and to provide a deep and throaty note.
Since these systems are uniquely designed to function at the rear of the vehicle, it operates without any noticeable lag and will produce full boost below 3,000 rpm. This is because the intake-tubing volume is about the same size as most traditional turbos that are front-mounted with an intercooler. The system is a true bolt-on kit that can usually be installed in an afternoon. In an F-body, the intake tubing is routed under the car on the driver's side. The tubing's exposure to ambient air alongside the car also serves to cool the charge. Tests have shown that turbo outlet temps with 5-psi boost measured 175 degrees F (at the rear of the car) and dropped to 115 degrees F at the intake discharge up front. The pressure drop was 1/4 to 3/4 psi. The bottom line is that the intake tube acts as an intercooler, dropping the rear-mounted turbo temp (which is already lower than engine compartment installations) about 50 percent and with a very small drop in psi.
To lubricate the turbocharger, Squires designed a system that taps into the engine's pressurized oiling system (above the oil filter). The pressurized oil travels through 12 feet of tubing back to the turbocharger. From the turbocharger, an electric oil pump removes the oil and pushes the lube forward to the engine and into a fitting in the center of the oil cap, where it drops back into the crankcase. Each time the lube travels up and back through the tubing it is cooled by ambient air.
The result is that you can realize huge horsepower and torque gains after a single day's work. The STS Turbo kit keeps your car stock in appearance, while retaining its original drivability. And oh yes, in most cases your fuel economy will stay the same or improve (in most cases, fuel economy improves 2-3 mpg). That is, of course, if you can keep from mashing the fun pedal.
The Truth is in the Numbers
STS makes kits for LT1 and LS1 Camaros. STS stresses that tuning is critical for all of its kits. For LS1 tuning information, STS recommends and sells Nelson Performance Programming.