Because of the additional modifications, including cylinder heads and a camshaft, the manufacturer’s tuning software wasn’t sufficient for this project. A custom tune was created at Stenod Performance and the Corvette delivered 508 hp and 439 ft-lbs of torque at the rear wheels through an automatic transmission. This was on a Mustang dyno that typically isn’t as optimistic as comparable chassis dynos from other manufacturers. That’s a significant 170 hp/110 ft-lbs jump over the baseline 338 hp/329-ft-lbs numbers.
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So, while complete turbo kits aren’t as plentiful as the range of supercharger systems, they can be created by essentially running enough tubing between the basic elements: turbocharger, wastegate, blow-off valve, and intercooler.
Real-World Project: Lingenfelter System
This project is the installation of the Lingenfelter Performance Engineering’s twin-turbo system on a Corvette Z06 (re-bodied by Specter Werkes/Sports). Although it is a system Lingenfelter has installed a number of vehicles, it’s not exactly an off-the-shelf kit. Because of the natural variances between production vehicles, Lingenfelter custom-fits elements like the water and oil lines after the turbochargers are installed. It’s a very precise, well-engineered system, but again underscores the difficulties in developing a true bolton turbo kit. With that in mind, this installation should be seen as representing the common components, connections, vehicle modifications, and other details that are common to all turbo systems. The caveat is that the system is specific to Lingenfelter Performance Engineering and the Corvette Z06. In other words, it should be viewed as a general overview of the parts and procedures involved, but by no means a definitive blueprint for all LS-powered vehicles. It should also be noted that this installation does not show every procedure, but highlights primary procedures and details.
The Lingenfelter system is designed for use in cars driven primarily on the street, so it works around existing vehicle systems and components. There was no sacrificing of air conditioning, power amenities, or anything like that. In a nutshell, it uses a pair of medium-size Garrett water-cooled, oil-lubricated ball-bearing turbos and an air-to-air intercooler. Here are the basics:
- A single blow-off valve
- Custom air-to-air charge cooler
- High-capacity fuel injectors
- Kenne Bell Boost-A-Pump
- Upgraded oil cooler
- Custom Corsa/Specter Werkes low-restriction exhaust system
- Custom tuning
Although boost is always tunable, the base system delivers about 10 to 12 pounds of boost to help the 7.0- liter engine produce 800 hp. More importantly, Lingenfelter’s package for the twin-turbo system includes rebuilding the high-compression LS7 engine with stronger internal components, lower-compression (9.0:1) pistons, and a number of other related details. The turbo system isn’t installed until the engine is removed, rebuilt, and reinstalled (all the work is performed at Lingenfelter’s Decatur, Indiana, shop). One of the benefits of the system for many customers is improved fuel economy in “normal” driving conditions. That’s mostly due to the engine’s lower compression ratio and the lack of parasitic drag; the turbochargers don’t affect drivability or fuel economy until they start generating boost.
An advantage to having the work performed at Lingenfelter’s shop (or any reputable shop that does custom turbo systems) is experienced fabricators. The minor, yet important, vehicle-to-vehicle variances between otherwise-identical vehicle models typically requires fabrication work that is not easily accomplished in a home garage.
Whether it’s a true bolt-on system or a blend of bolt-on and custom fabricated, such as the Lingenfelter system, installation takes time— perhaps two or three times as long as a bolt-on supercharger system. Keep that in mind (and its implication on labor costs at the installation shop) as you consider such a modification.
Custom Turbo System Fabrication
Rather than a system designed for racing, the vehicle’s owner, DiabloSport chief Mike Wesley, wanted an integrated system for the street. That meant the system had to work around existing vehicle systems and components. There was no sacrificing of air conditioning, power amenities, or anything like that. Wesley turned to Stenod Performance to design, fabricate, and install a custom system. It uses a pair of Garrett ballbearing turbos and an air-to-air intercooler. Initially, because the turbochargers were blowing into a stock LS2 engine, boost was kept to a detonation-avoiding 5 pounds. That was enough to deliver tread-melting performance from all four of the all-wheel-drive TrailBlazer’s tires.
Soon, Wesley returned to the Stenod shop for a power boost. The engine was removed and rebuilt with the requisite forged internals and lower-compression pistons, as the wick would be turned up on the turbos to deliver approximately 10 to 12 pounds of boost. The original Garrett turbochargers were retained, but the wastegate actuators were swapped to allow the greater boost (a boost controller was not used).
Basics of the system and supporting hardware include:
- Two Garrett GT28R ball-bearing turbochargers with integral wastegates
- One TiAL 50-mm blow-off valve
- Custom air-to-air charge cooler
- 60-lb/hour fuel injectors
- Walbro 355-lph in-tank fuel pump
- Stock radiator with fourthgeneration F-car cooling fans and C6 Corvette fan-control unit
- SLP Performance low-restriction exhaust system
- Retention of the stock mass air metering system, but with a 3-bar MAP sensor
- Re-programmed factory controller with HP Tuner
On a completely custom build, every inlet, discharge, and intake tube requires fabrication. If you are seeking to have a custom turbo system made for your car should do so only through a shop with similar experience. Inspecting other customers’ cars and interviewing them about their experience are musts before entrusting your car and money to any shop. The design and fabrication of the TrailBlazer’s system required turbocharger mounting brackets, air intake flow tubes, discharge flow tubes, intercooler tubing, and exhaust tubing. Additionally, a number of oil and coolant hoses were routed into and away from the turbochargers, requiring modification of the engine’s coolant lines to merge the turbochargers’ cooling lines with the engine’s water system.
One of the more advantageous aspects of the system’s design is the mounting of the turbos out of the engine compartment. They are located down and away from the engine, effectively straddling the transmission. This placement takes the turbos away from the exhaust manifolds, saving the time and money of fabricating custom manifolds, while also reducing underhood heat. In fact, factory shielding on the underside of the vehicle, where original exhaust components were located, provides an excellent thermal barrier for the turbochargers.
Upon completion of the upgraded turbo system, the TrailBlazer was tested on an AWD-capable chassis dyno, where it produced more than 600 hp and 550 ft-lbs of torque to all four wheels. It was stunning performance for a vehicle that is driven daily, but performance that is well within the capability of a carefully designed, installed, and tuned turbo system.
The STS Option
As described in Chapter 3, Squires Turbo Systems (STS) offers a nonconventional method of adding a turbo system to a vehicle. Rather than mounting the turbocharger(s) on the exhaust manifold(s), it is moved far back on the underside of the vehicle, typically near the rear axle. The reasons for this include reduced underhood temperature, lower air-charge temperature, lower cost (an STS kit eliminates the need for expensive, purpose-built headers or exhaust manifolds) and, perhaps most importantly, comparatively easy installation.
Because the turbo and its plumbing are mounted beneath the car, there is far less need for fabrication and relocation of underhood components. In most cases, installing an STS kit is comparable to a centrifugal supercharger—and perhaps slightly easier and less time consuming.
When STS turbo kits first hit the market, skeptics wondered whether a turbo hanging near the rear axle was the best place for it, citing concerns over its exposure to the elements, rogue road debris, and water ingestion. Generally speaking, those fears have proven to be unfounded. In fact, the systems have proven to deliver on their promise of lower temperatures, both at the throttle body, overall, and under the hood. It seems the long tubing of the system, running front-to-rear on the vehicle, delivers a passive intercooling effect. Many of STS’s kits include conventional intercooling systems, because the high compression ratio of stock LS engines demand it. Of course, like any turbo system, an STS system is adjustable, allowing you to adjust boost pressure to make more power.
The following basic installation procedures of an STS kit are performed on an LS1-powered Pontiac GTO (similar to the Holden Monaro). Of course, different vehicles and different engines require different installation procedures, but the steps outlined here provide an excellent look at the basic mounting of the turbo and routing of its inlet and outlet plumbing.
One of the unique aspects of the system is an electric pump that circulates oil between the turbo and engine. This isn’t always necessary with a conventional turbo system, but definitely required on the STS kit, as there’s no way gravity would return oil to the engine.
For the record, the project car produced 480 rwhp, with a Garrett G-67 turbo producing about 8 pounds of boost. The LS1 engine was internally stock, but was equipped with an LS6 camshaft and valvesprings.
Building a Race Car around a Turbo System
The custom turbo kit on the TrailBlazer SS and the STS turbo kit mentioned earlier represent a system designed to fit within the confines of essentially stock vehicles. For vehicles intended more for the drag strip than the street, accommodating the turbo system is the priority, with the vehicle’s bodywork and chassis modified to support it. For the popular “street car” and pro-modified-style classes, the engine system typically includes one or two very large turbochargers, a custom intake system, and a large-capacity, liquid-to-air intercooling system (often using an interior-mounted reservoir of ice water). Simply put, these race cars are built around the turbo system, with priority given to the desired location of the turbo(s).
“We start with where the turbochargers are going to be mounted, and go from there,” says Stenod’s Joe Borschke. “The customer tells us, for example, that the rules for his class allow a 106-mm turbo. That’s a big turbo and it’s going to take up a lot of room, as is the tubing routed in and out of it.”
Although there’s not a necessarily perfect location to mount a turbocharger, Borschke typically mounts them at the very front of the bodywork, exposing the air inlet side to the atmosphere.
“For a race car, you want as much exposure to fresh air as possible, as any restriction will affect the maximum boost,” he says. “It’s for this very reason that you wouldn’t duplicate such a system on a street car; you need adequate air filtering on the street.”
Another important aspect in race car turbo design is optimal wastegate location, with tubing that avoids sharp bends.
“The wastegates have to be priority-fed,” says Borschke. “Air must go through the wastegates first [before the turbochargers] to maintain proper boost control.”
As for those large intercooler tanks typically seen in the interiors of race cars, there are several reasons for locating them in the cabin. First of all, they are just plain large and don’t fit easily in the engine compartment. Also, when filled with ice water, they’re quite heavy, so mounting them in the interior helps distribute weight more evenly on the chassis.
Written by Barry Kluczyk and Posted with Permission of CarTechBooks