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Added Horsepower and Reliability for Your 6.7L Ford

If you’ve ever heard of a Duramax or 6.0L Power Stroke equipped with a Powermax turbo, you’ll completely understand this article. Over the years, Garrett’s Powermax line of turbochargers have proven to be great replacement units for trucks with mild to moderate fuel and tuning upgrades. On the Duramax side, the benefits of running the Stage 1 Powermax (GT3794VA) include an uptick in turbo size with no negative change in drivability, a budget-friendly price tag, and a signature, high-pitched whistle out the tailpipe.

Enter the 6.7L Power Stroke crowd—specifically 2011-2014 Super Duty owners. These trucks came with the single sequential (dual compressor wheel) Garrett GT32 SST that was notorious for premature failure (oftentimes with nothing more than a hot tuner in the mix). On top of its rampant failure rate, the 46mm inducer turbo ran out of steam well before 3,000 rpm, essentially choking off the horsepower potential we now know the 6.7L is capable of (650-rwhp with stock injectors, an aftermarket turbo, and a second high-pressure fuel pump).

Searching for a readily available turbo that could add both power and reliability to 6.7L powered Blue Ovals yet retain the engine’s abundance of low-end torque, the Power Stroke gurus at Elite Diesel Engineering chose to produce a bolt-on kit around the Duramax-intended GT3794VA. With a turbo pedestal adapter, high-flow up-pipes, and new air intake and intercooler plumbing, the all-inclusive system improves the performance of the 6.7L Power Stroke in every way.

We recently stopped by Flynn’s Shop in Alexander, Illinois to watch a 2012 F-350 be graced with one of Elite’s GT3794VA kits. With a customer looking to ditch the factory turbo before it had a chance to fail, add considerable horsepower, and (perhaps most important) trade in a howling exhaust note for an ear-piercing whistle, this turn-key upgrade didn’t disappoint. If you’re in the market for a more reliable, higher flowing, and distinct sounding turbo for your 2011-2014 6.7L Power Stroke, this might be the charger for you. DW

Elite Diesel Engineering’s GT3794VA turbo kit (which also works with the larger GT4094VA) came with everything the folks at Flynn’s Shop needed to bolt the Stage 1 Powermax onto a customer’s ’12 F-350: turbo pedestal adapter, 2-inch up-pipes, two-piece 3½-inch to 4-inch downpipe, and all boots, clamps, oil and coolant lines, fittings, and fasteners. Note that this photo doesn’t show the intercooler piping, air intake plumbing, air filter, or fuel filter relocate system that was also included in the kit.

Before any work was performed under the hood, the truck’s aftermarket front bumper, brush guard, and grille were removed, followed by the draining of both cooling systems. Remember, on a 6.7L Power Stroke there is a cooling system dedicated solely for the engine, and a completely separate cooling circuit for the EGR system, transmission, and water-to-air intercooler.

With the airbox and EGR system’s coolant supply line removed, the turbo boost sensor was unplugged and all upper intake bolts were loosened. Once the upper intake was lifted off of the engine, both intake manifold inlets were taped off.

Thanks to Elite’s turbo system including a replacement cold-side intercooler pipe, the factory piece could be tossed in the trash once it was removed. This is a common failure point on the 6.7L Power Stroke, as the plastic pipe is known to explode (typically in the middle) under high boost or extreme heat conditions.

Next, the cast-aluminum lower intake assembly was loosened, but before it could part ways with the engine completely the factory crankcase ventilation hose had to be disconnected from the backside of it. Then the factory hot-side intercooler pipe was pulled, as it would also no longer be needed.

To access the factory up-pipe nuts on the passenger side of the engine, the inner fender well was removed, followed by the up-pipe (shown). In order to gain ample room to pull the driver side up-pipe, the upper and lower portions of the factory downpipe were removed next.

With all intercooler and exhaust plumbing disconnected from the factory turbo, its coolant and oil lines were removed (oil supply line shown), along with the factory wastegate solenoid harness, which was no longer needed. Then all four turbo pedestal bolts (two up front, two in the rear) were loosened via a 13mm socket.

Once the turbo was free in the lifter valley it was a time to squeeze it out. With the wastegate diaphragm hitting in the rear and the turbo’s oil feed line not easily clearing the high pressure fuel lines up front, it takes a bit of finesse to wrestle the stock turbo off of the engine.

Which turbo would you rather have, the factory 46mm GT32 SST (left) or the 64.7mm Stage 1 Powermax? While the dual compressor wheel design of the GT32 SST looks good on paper, it falls short in the real world, where a conventional style turbocharger with a single 60-to-66mm compressor wheel provides an adequate operating range at virtually any engine speed. What the GT32 SST effectively did was minimize the 6.7L Power Stroke’s power band. Anything above 2,800 rpm (or so) and the stock turbo was spent—and when subjected to aggressive tuning its lifespan was on borrowed time.

Being that the 6.7L Power Stroke and (6.6L) Duramax V-8’s possess similar displacements, it’s no wonder the GT3794VA Stage 1 Powermax performs as well as it does when bolted to a ’11-’14 Ford. Dyno testing has shown gains of up to 80-rwhp when a higher flowing turbo such as this one is added to a tuned 6.7L.

A 10-blade turbine wheel coupled with Garrett’s AVNT variable geometry turbine housing leads to the jet-like sound the GT3794VA emits. It’s also why superb low-end drivability (responsiveness) is retained.

Because the 6.7L Power Stroke receives its turbo vane position information from the exhaust back pressure sensor, the turbo vane position sensor (which is required for Duramax installations) was removed from the GT3794VA, along with the port receiving a plug. However, the variable vane actuator (far left) would be utilized, and the factory Ford harness plugged right in.

Increasing exhaust flow out of the heads substantially are these 2-inch (od) up-pipes (vs. the 1.55-inch od stockers). They’re made out of heavy wall (0.120-inch thick) 304 Stainless Steel for utmost durability and bolt right up to the factory exhaust manifolds.

With the factory turbo out of the way, all leftover dust and debris was removed from the valley with a shop-vac, followed by the installation of the supplied billet-aluminum turbo pedestal adapter. The guys at Flynn’s told us it’s easiest to set the driver side up-pipe on its respective exhaust manifold studs before the turbo goes on (hence its positioning in this photo). Note that the oil feed (passenger side) and coolant return ports (driver side) have been marked on the turbo pedestal adapter.

For added insurance, reference marks were added to the oil drain and the oil drain flange to make sure the turbo’s oil drain was clocked correctly once everything was placed on the engine. From there, all supplied oil and coolant fittings were installed on the turbo.

After the turbo was placed onto the pedestal adapter, the factory mounting bolts were torqued to spec and the supplied braided stainless coolant and oil lines were connected. Then it became very apparent why Elite’s turbo kit came with a fuel filter relocation bracket…

With the compressor outlet on the Powermax turbo sitting less than 2-inches away from the factory underhood fuel filter housing, it was obvious it had to be relocated in order for the hot-side intercooler pipe to clear. Using the supplied fuel hose, bracket, and mounting hardware, the fuel filter housing was relocated toward the brake master cylinder along the firewall. This relocate kit allows you to continue to utilize the OE-quality Motorcraft fuel filter.

Tight quarters is par for the course with any turbo swap on a 6.7L Power Stroke. While a lot of folks would prefer to pull the cab, the folks at Flynn’s are content performing the job without doing so. Here you can see the passenger side up-pipe being tightened to the exhaust manifold.

Next, the top portion of the supplied two-piece downpipe was attached to the turbo. The stainless steel downpipe transitions from 3½-inch to 4-inch diameter before hooking onto the rest of the exhaust system.

Back on top of the engine, the intake elbows were next on the to-do list. The elbows feature high flow transitions where they meet up with the intake manifolds. On the back side of the driver side unit, Elite includes a provision to tie the engine oil and transmission fluid dipstick tubes together via a bracket. Essentially, the two tubes mount similarly to how they did from the factory (anchoring to the rear of the upper intake).

The passenger side intake elbow incorporates the factory turbo boost sensor, which originally plugged into the upper intake assembly. After the boost sensor was in place, the factory coolant line for the heater core was reinstalled.

Installation of the intercooler piping proved to be a snug fit. Here you can see the 3-inch hot-side pipe going on. The cold-side, twin tube pipe measures 3¼-inch in diameter and connects to the water-to-air intercooler outlet via a supplied 90-degree boot. All piping is made from 0.120-inch wall aluminum, features bead rolled ends, and installs using supplied high-strength silicone boots and T-bolt clamps. Shipped raw, this truck’s particular piping configuration was powder coated red by Bill Matthews Auto Body in Springfield, Illinois.

Once the intercooler piping and air intake assembly were installed and snugged up, all remaining coolant lines were reconnected or bypassed (where need be), and then both cooling systems were topped off. Then the truck was started, inspected for leaks, and taken for its first test drive.

To get the most out of the Powermax turbo, custom tuning will be employed. The calibrator of choice for this customer is Gearhead Automotive Performance. Proper tuning for a variable geometry turbo swap is important in getting maximum performance and drivability out of the charger you’re using (be it a GT3794VA, GT4094VA, GT37, or even the factory GT32 SST).

And there you have it: added horsepower, reliability, and cosmetic appeal with Elite’s Powermax turbo kit sitting under the hood. It’s worth noting that since Ford ditched the GT32 in favor of the conventional (more reliable) GT37 Garrett turbo for the ’15 model year, most aftermarket companies now base their ’11-’14 turbo swap kits on that platform. And to be honest, going with a ’15 style (stock or modified) charger is both easier and in most cases more affordable than installing a GT3794VA. However, this particular customer wanted the signature whistle that the GT3794VA is known for. After riding in the truck, he definitely got his wish, as it sounds downright wicked.

Sources:
Elite Diesel Engineering
(866) 631-8518
www.elitedieselengineering.com

Flynn’s Shop
(217) 478-3811

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Garrett
www.turbobygarrett.com

Gearhead Automotive Performance
(979) 703-7338
www.gearheadautomotiveperformance.com