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, forged steel 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 time intensive 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 gravity fed 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 twin turbo 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 re-imaging the converter system, because the close-coupled, high-mounted 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.

An interesting detail on this system is the reuse of the vacuum port that used to actuate the factory’s two stage 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 air intake 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.