Subterranean Turbo System Install

The STS Turbo system for the '98-'02 LS1-powered Firebirds retails for $3,995 and comes complete with everything needed to bolt on well over 100 rear-wheel horsepower. Included in the kit are a Garret turbocharger, a patented STS oiling system, a TiAL wastegate, HPC-coated piping, a K&N air filter, and all the wiring, tubing, stainless hardware, and clamps to allow an enthusiast to add some serious power to his Bird in about a day's time. A bound instruction manual is included with detailed instructions and quality color photographs.

Our apologies, as the initials STS don't mean Subterranean Turbo System, but instead stand for Squires Turbo Systems, founded by Rick Squires in 2003. The fledgling Orem, Utah-based company's turbocharger systems are classified as rear and/or remote turbo systems, dwelling in the spot normally occupied by the muffler and/or after-cat exhaust.

Traditional turbo systems, be they from the OEM manufacturers or the aftermarket, have been placed under the hood, as close to an exhaust source (as it exits the engine) as packaging allows. Given these obvious differences in application, let's first examine the basics of a traditional turbo system, and then Rick Squires will explain how his goes against the perceived location requirements of turbo placement yet works well and even offers advantages over underhood turbos.

A turbocharger has one moving part, the turbine shaft, which is powered by exhaust gases. Since exhaust gases have a higher velocity close to the exhaust valves, conventional wisdom places it under the hood. After spooling up the turbine shaft, air is pulled into the compressor housing and sent out the side of the turbo to be fed into the intake tract. The shaft that spins the turbine and the shaft's bearings are cooled by engine oil, fed from the block. Exhaust gases never breach the intake tract, as the exhaust is simply the force function to turn the wheel. Heat generated at the turbo comes primarily from the exhaust charge that it sees, followed by the thermal energy imparted to the compressor housing by the spinning of the turbine shaft and the heat generated by the compressor side as the air is spun up (compressed and boosted).

The Garret T04E turbocharger comes assembled from STS. Teflon tape is utilized to seal the supplied brass fittings. After ensuring the tape doesn't protrude past the threads, a 90-degree elbow is installed on the compressor side (bottom left) for wastegate boost control, and another 90-degree elbow, oil check valve (pressure switch), and 90-degree elbow install in the center for the turbine shaft.

This compressed air enters the engine at a factor above atmospheric conditions, thus forcing more air into the cylinders. The amount of air over and above the standard barometric pressure is what is defined as boost pressure, which is controlled by regulating the exhaust flow across the turbine via the wastegate (dump the exhaust and slow down the turbine speed). Left unregulated, boost will compound and destroy an engine in short order. Turbochargers are engineered based on the size of the engine that they will be on as well as the volume of compressed air needed. A properly sized and engineered turbocharger system will see little "turbo lag" and will address heat management of the compressed air via an aftercooler or other measure such as alcohol or methanol injection. Sounds great, right? But what if space is tight under the hood?

In today's cars, including the LT1- and LS1-powered F-bodies, underhood space is extremely limited. Sure, turbocharger systems exist for these vehicles, but the innovative approach that STS took in designing a system for your late-model F-body garnered the company the coveted GM Design Award for Best Performance Product at the '04 SEMA show. That's a high accolade, which makes this system worthy of a closer look at its origins, engineering, and development.

And who better to fill us in than Rick Squires, owner of STS? "I didn't start the business to go after the performance F-body market--it just sort of happened," Squires says. "Originally, I took my mechanical background and wondered why nobody ever designed a turbocharger system for late-model trucks that eliminated the two large problems with factory systems--underhood room and heat.

Here, the turbine or input side of the compressor shows that this is an 0.81 A/R housing. The fitting seen on the bottom right is installed and functions as the output fitting for the engine oil that will be returned to the valve cover after it has been pumped through the housing to cool and lubricate the turbocharger bearings.

Assembly of the turbo begins by loosening and removing the compressor and turbine housing bolts (six each) with a 1/2-inch wrench. As you pull out each bolt, apply the supplied antiseize compound to the threads and turn each one back in until it is several turns away from being hand tight. Once done, rotate the compressor and turbine housings to make sure they swivel smoothly. The bolts were loosened to properly "clock" the housing, which is important in the exhaust pipe installation stage, but also necessary as the rest of the housing is installed.

Next up is mounting the exhaust inlet pipe to the turbine-housing inlet. A metal exhaust flange gasket is placed between the pipe and housing and four 2-inch x 9/16-inch head bolts are slipped through.

"A salesman for a large Toyota dealership in Salt Lake City purchased an '01 Toyota quad-cab 4x4 with a 3.4L engine. He wasn't impressed with the performance of the TRD superchargers that a few of the sales guys had, but was going to get one anyway. Then a friend suggested he contact me about a turbocharger system. I looked at the truck and there was enough room to do one under the hood, except that it wouldn't be able to pass emissions.

"Once I got the truck on a lift, it dawned on me that the area where the muffler sat would be a great place to mount a turbo. Eliminate the muffler, have the exhaust pipe that fed the muffler now feed exhaust gases to the turbo--a prototype later and the business began.

After putting on the lock washers and nuts, the stainless nut and bolt combination is hand-tightened before using two 9/16-inch wrenches. A star-pattern should be used to tighten the bolts evenly so that the exhaust gasket compresses equally, ensuring a leak-free seal.

The TiAL 38mm external wastegate is installed next. It mounts to the exhaust inlet pipe and seals by utilizing a traditional composite gasket and a beveled flange. This beveled valve and valve seat flange mounts inside the wastegate.

Once the flange is installed, the gasket is inserted and the assembly is attached to the exhaust inlet pipe with a 1/2-inch wrench using two 2-inch-long x 1/2-inch head bolts, with lock washers and nuts. Wastegates function to regulate the amount of exhaust gasses passing through the turbine wheel. More on boost control later.

"After successfully launching a line of turbo systems for Toyota and GM trucks, a friend convinced me to design one for his LT1 Camaro. Finding success with that system, the LS1 crowd started beating a path to our door, demanding one of their own. We prototyped the LS1 system by using a locally owned '99 Camaro. The base LS1 package uses a Garrett T04E turbocharger with a 60-1 compressor and an 0.81 A/R turbine housing.

"A/R refers to the area of the scroll divided by the radius of the centroid of that area from the center of the shaft. Basically, the scroll starts far away from the center of the shaft and has a large diameter hole. As the exhaust passage scrolls around toward the turbine wheel, it gets closer to the center and the passage (area) gets smaller. In a nutshell, it is shaped like a curved funnel. The smaller the A/R number, the higher the velocity of the gasses will be when they hit the turbine wheel.