LS Engine Turbocharger Projects: Step-by-Step

The turbo system is designed to mount the turbochargers directly to custom, heavy-duty exhaust manifolds. In the low-slung Corvette chassis, that still puts them at the bottom of the engine compartment, which helps keep heat farther away from the engine and air-intake system.

Lingenfelter’s basic system uses a pair of mid-size Garrett GT30-series water-cooled, oil-fed ball bearing turbochargers and Forge wastegates. The medium-size bodies of the turbos make them ideal for easier fitment and quick spool-up. The A/R ratio, as noted on the casting seen here, is .50:1.

This turbo installation project takes place on a Specter Werkes/Sports GTR built around a Corvette Z06. All of the mechanical work was performed at Lingenfelter Performance Engineering’s Indiana facility.

Prior to installing the turbo system, Lingenfelter removes the Z06’s LS7 engine and rebuilds it to suit the demands of turbocharging. That involves rebuilding the short-block with a new, forgedsteel crankshaft, forged-steel connecting rods, and lower-compression, 9.0:1 pistons. The heads also receive high-temperature-resistant Inconel exhaust valves.

The first evidence of custom fabrication on the kit is the welded-on elbow added to each turbocharger’s air outlet, which is necessary to orient the outlet toward the front of the vehicle.

A thick, 3/4-inch flange is attached to the exhaust manifold, where the turbocharger mounts. This is necessary to prevent warping under the extreme temperatures generated when the system is producing maximum boost. Also note the heat shield attached to the manifold.

Turbo systems invariably require custom or modified exhaust systems, so before installation began, the original system was removed and set aside.

One of the other pre-installation procedures involves prepping the engine for the oiling requirements of the turbos. That involves swapping the stock oil cooler for an aftermarket model, fitting a scavenge pump to pull returned oil from the low-mounted turbos and adding a feed line (seen here) to the oil pan that sends the circulated oil back into the pan.

The system’s installation started with bolting on the exhaust manifolds. With the hood removed and considerable chassis clearance on the Corvette, it was easy to do from the top of the engine compartment. Other vehicles require careful installation of the manifolds from the bottom of the engine compartment.

The all-important oxygen sensors are threaded into the exhaust manifolds next, as doing so later would be more difficult with more of the turbo system’s components in place. Wideband sensors are installed for more precise part-throttle tuning.

With the exhaust manifolds and their oxygen sensors in place, the first turbocharger is hoisted into position, sliding onto the mounting studs protruding from the exhaust manifold’s mounting flange. In this photo, the passenger-side turbo is being installed.

Lingenfelter uses many hard lines in the system, including the oil-feed and oil-return lines at the turbo, which require custom fitting to account for the slight variances among vehicles. After the first turbocharger was installed, for example, this line was measured at cut to fit the oil-feed line to it.

The hard oil-feed line wraps under the oil pan and up to a T-junction in an aftermarket oil cooler. The bottom fitting is reserved for the driver’s-side turbo’s oil-feed line.

The installed oil-feed line is seen routing away from the turbo and along the oil pan rail. Installing the line at this point in the project is necessary, because access to it would be almost impossible after the down tube and other sections of the system are installed.

With the passenger-side turbo and its oil-feed line in place, the driver’s-side turbo is installed and its oil-feed line attached.

At the other end of the turbos’ oiling system is a scavenge system that draws oil cycled through the turbochargers back into the engine’s oiling system. Because the turbos are mounted low on the engine, gravity is not sufficient for draining to the oil pan, so Lingenfelter designed a small oil tank that collects the return oil from the turbos and, with the help of an electric pump, draws it out and back into the oil pan.

The turbochargers are also water cooled, which requires tapping into the vehicle’s cooling system for feed and return. Inserting a junction in the heater hoses does the trick. As seen here, it’s double-clamped on both ends to ensure a leak- and blow-proof seal.

To make installation easier in the tight confines on the bottom side of the engine compartment, banjo-type fittings are used to connect the coolant system to the turbochargers.

Like the oil lines, the water lines to and from the turbos are hard lines. They’re also routed around the oil pan. This configuration is more timeintensive to fabricate and install, but if the lines were simply run directly under the pan, they’d be susceptible to damage if the vehicle were to scrape the ground.

Next, the down tubes (the pipes that connect the exhaust outlet of the turbos to the vehicle’s exhaust system) are installed, but not before they’re test-fitted to ensure there are no interference issues with any of the other turbo system or chassis components.

Although a metal gasket was used between the turbochargers and exhaust manifolds, the down pipes are mated to the turbos with Permatex Ultra Copper high-temperature silicone gasket maker. It is spread liberally on the mounting flange.

With the copper gasket maker on the flange, one of the down tubes is cinched down against the turbocharger. Note how both down tubes are further supported by mounting tabs that attach to the transmission bell housing.

The custom oil-scavenge tank also mounts to the bell housing. The hard lines feeding the tank carry gravityfed oil from the turbochargers, while the large flexible hose draws out the oil with vacuum pressure from a pump mounted at the front of the engine. The oil is then reintroduced to the engine oil circuit.

From under the Corvette you can see the basic installation and orientation of the twinturbo setup, prior to the fitting of the air-intake and air-discharge tubes. Look closely and note the careful routing of the hard lines for the oil and water systems, as well as the unique oil-scavenge tank. From here, the installation focuses on the intake tubes, intercooler, and reinstallation of numerous engine/exhaust system components.

The silicone hoses are carefully routed from the turbochargers along the chassis rails, with numerous checks and inspections to ensure they don’t bind or interfere with the suspension and steering systems.

Filter-capped intakes are mounted in the front corners of the front fascia. The air-discharge tubes from the turbos feed the intercooling system’s heat exchanger that is to be located in front of the radiator.

The intercooler’s heat exchanger slides down in front of the stock radiator, necessitating the relocation of the oil cooler’s heat exchanger. A Y-pipe connects both outlets of the exchanger and feeds the air charge straight into the throttle body. Like other aspects of the installation, the Y-pipe is custom-fitted to each vehicle. After that, the heat exchanger and intake tube are painted black.

When the intake tubes are routed and securely attached, the project moves into the final stages, with buttoning up a myriad of details, including installing the mass air sensor (seen here), reconnecting the fuel system, and performing a number of wiring duties.

The final major task in the installation involves re-installing the exhaust system. As is the case with most turbo installations, a modified exhaust system is required. In the case of this Z06-based project, it also required reimaging the converter system, because the close-coupled, highmounted catalytic converters on the stock exhaust system were eliminated. Lingenfelter’s solution involves using a pair of aftermarket converters and a lightly modified Corsa C6 Corvette flow tube to fit within the vehicle’s underbody tunnel. The rest of the exhaust system was modified in order to keep the mufflers in the stock location.

Fuel-system upgrades are necessary for an engine producing about 300 more horsepower than stock. To that end, Lingenfelter installs a set of 60-lbs/hr injectors and supports them with a Kenne Bell Boost-A-Pump fuelpump voltage amplifier.

An interesting detail on this system is the reuse of the vacuum port that used to actuate the factory’s twostage exhaust system. It now is used to actuate a fuel-pressure regulator mounted at the rear of the vehicle, near the fuel tank.

Lingenfelter uses flexible silicone hoses for the airintake tubes and the discharge tubes that feed the boosted air charge to the intercooler. They’re custom made a little longer than necessary to enable precise fitment with a little trimming.

Adding a turbo system to the TrailBlazer SS presents the same problem for many LS-powered vehicles: There isn’t a bolt-on kit available in the aftermarket (at least not as this book was published). A custom turbo system was designed, built, and installed by Stenod Performance. Fortunately, there was enough room under the hood and around the chassis to facilitate the installation with minimal impact on the surrounding factory components. As is the case with almost all intercooled forced-induction systems, the project began with the removal of the front fascia, grille, and headlamp components to enable mounting of the intercooler heat exchanger and related plumbing.

The turbo system includes a pair of Garrett GT28R watercooled, ball-bearing turbochargers. Seen here is one of the turbochargers mounted to an exhaust extension that bridges between the turbo and exhaust manifold. Because of this arrangement, the turbocharger is located at the bottom of the engine compartment, in the approximate area of the original catalytic converter. The lower mounting position not only reduces underhood heat, but the thermal barrier for the converter also provides heat shielding

Here is the passenger-side turbocharger/exhaust extension assembly attached to the exhaust manifold. Note the Y-fitting with large-diameter hoses at the center of the photo. It is part of the scavenge system that draws oil away from the turbochargers and back into the engine-oil circuit. Like the turbos described in the Lingenfelter installation earlier, the turbochargers on this system are water-cooled and externally lubricated. Because of the heat generated by the turbos, very durable, heavy-duty hoses, including braided lines, are used with AN-type fittings.

The other major component of the turbo system is the intercooler, which includes a custom heat exchanger built by Stenod Performance. It’s an air-to-air intercooling system, meaning the pressurized air from the turbo system simply flows through the exchanger and is cooled by air entering through the grille or from the electric cooling fans. There is no liquid coolant circulating in the heat exchanger, as would be the case with a liquid-to-air intercooler. Stenod started with a Bell core and built the inlet/outlet caps to fit the TrailBlazer. It mounts to a removable header that’s part of the TrailBlazer’s radiator core support, making installation and removal very simple.

When it came to the coolant lines for the turbochargers, the inlet and outlet hoses were routed from the aluminum hard-line sections of the heater hoses. That required drilling holes and welding fittings to the factory lines. There are other ways to tie into the factory cooling system to provide the same effect, but with one of the hard lines dedicated to inlet and the other a dedicated outlet, this method is foolproof, even if it required careful, labor-intensive aluminum welding.

With most of the coolant and oil lines routed and connected, the turbos’ air intake and discharge tubes are mounted. The relatively large chassis and generous ground clearance of the TrailBlazer SS allowed Stenod Performance to route them easily under the engine K-member, where they feed into the bottom of the intercooler heat exchanger.

The air intake filters are mounted as far away from the heat of the turbo system as possible; in this case, at the far corners of the front bumper cover. Note the vacuum hose attached to the intake tube. It’s part of a crankcase breather system.

The fabricated portions of the exhaust system also included provisions for oxygen sensors: one on each side, after the turbochargers. This system also incorporates oxygen sensors before each turbocharger, to satisfy the parameters for wideband tuning.

At the top of the engine, the intake tube is sandwiched between the throttle body and intercooler. It is a large, 4-inch-diameter tube to feed as much air as possible to the engine. The convoluted shape of the tube again demonstrates the careful, custom fitment required of each tube to fit with other factoryinstalled components. For vehicles that aren’t matched with an aftermarket turbo kit, such custom fabrication is the only option. Stenod Performance incorporated a TiAL 50-mm blow-off valve into the intake tube. A blow-off valve should be located in the intake section between the discharge port of the intercooler’s heat exchanger and the throttle body, which is right where this one is located.

The supporting elements of the turbo system are focused mostly on fuel requirements. They include a highercapacity, 355-lph tank-mounted fuel pump that required the removal of the fuel tank for installation. At the other end of the fuel system, a set of 60- lbs/hr injectors was installed in the intake manifold.

The stock radiator was retained, but the cooling fan assembly was swapped with the twin-fan setup from an LS1-powered fourth-generation F-car. The fans are driven with the controller from a 2005-later Corvette, because it offers almost infinite adjustability when tuning the engine, including varying the fan speed to suit different demands. Most other electric fans, such as the fourth-generation F-car fan, are not adjustable—when they’re on, they’re on full-blast.

This underhood shot of the STS-equipped GTO reveals no clues that there is a turbocharger installled, apart from clearly non-original air intake that snakes down and under the engine compartment. The uncluttered appearance is a hallmark of the STS kit, as it doesn’t require tricky fabrication to squeeze the system beneath the hood.

Here’s an STS kit all laid out. Basically, the kit is comprised of tubing, clamps, and the hardware required to install the turbo and its supporting components. Not seen here is a separate intercooling system that is partnered with many of the kits. Additional components are also required, including higher-capacity fuel injectors and a fuel-pump booster. (Photo courtesy Squires Turbo Systems)

At the top of this photo, the Y-pipe illustrates the merge of the left- and right-hand exhaust outlets and its flow rearward to the turbocharger. The separate tube at the right is the flow tube carrying the boosted air charge to the intercooler and, after that, to the engine. The length of the tubes and their distance from the exhaust manifolds provide a passive intercooling effect.

Looking up at the chassis, with the left-rear tire on the right side of the photo, you can see STS’ mounting location for the turbocharger. It’s the location of the original muffler, which is eliminated with this system (although that is not true for all STS kits). A benefit of this mounting position is the factory heat shield that was originally designed for the muffler.

There’s no down pipe or other exhaust system with STS’s GTO kit. An exhaust outlet pipe simply mounts where the exhaust or down pipe would attach on a conventional system. The exhaust note with this design is acceptable and, the closecoupled catalytic converters that are mounted right off the exhaust manifolds are retained.

This view looking up at the front of the car shows the inlet pipe from the turbo coming in from the right, with the outlet to the engine intake on the left. What’s missing in between is the heat exchanger for the intercooler.

An oil-feed line for the turbo is added at the oil filter mounting pad, tapping into an existing, but unused port. A return line is also required and routes back through the oil-fill hole in the valve cover. An electric pump scavenges the oil from the turbo, forcing it back into the engine.

The unconventionally mounted turbo system requires conventional upgrades to the fuel system and ignition system. The LS1-powered GTO sufficed with a set of 42- pound injectors and a Kenne Bell Boost-A-Pump. Also, NGK TR6 spark plugs replaced the originals.

Here’s a look at the finished installation. The blow-off valve is visible, but the system doesn’t hang much lower than a regular exhaust system. A vehicle with a solid rear axle would benefit from better, over-the-axle tube routing, but the independent rear suspension of GTOs/Monaros, G8s/Commodores, and fifth generation Camaro demands tubing that runs under the axle.

Here is a typical turbocharged race car under construction. The turbochargers were mounted up front on a fabricated brace, replacing the original bumper beam. Note how the turbos are fed by reversed, marinestyle headers, with the wastegates located before the turbochargers. The air outlets from the turbos merge into a single, large-diameter tube that is routed on the outside of the engine compartment (underneath the passenger-side front fender) to the passenger compartment, where it is cooled by a large, liquid-to-air intercooler. The cooled air charge is then fed through a hole in the firewall to a reversefacing inlet atop the intake manifold. This is not designed for street use, as all of the typical accessories found on a street car are eliminated to make room for the turbo system’s tubing.

Another race car under construction shows a smaller, front-mounted intercooler and more conventional mounting of the turbochargers. But while this setup seems tame when compared with the twin-turbo setup outlined in the previous photo, it nonetheless involves removing the bumper beam and other underhood accessories to support the system’s components. Again, this is not a system for the street.