Instant throttle response, big torque, and the ability to get loads moving in a hurry were great selling points for the 2011 Super Duty. Thanks to a variable geometry turbocharger, reverse flow cylinder heads, and a Bosch injection system utilizing piezoelectric injectors, Ford’s 6.7L Power Stroke V-8 packed 400hp and 800 lb-ft of twist when it debuted. However, power ratings on paper don’t always pan out in the real world. With roughly 50-percent of all modern diesel trucks being equipped with some sort of programmer or other power adder, it didn’t take long for 6.7L Power Stroke owners to find the weakest link in the chain: the Garrett GT32 SST turbo.
Equipped with variable geometry technology, a ceramic ball-bearing center cartridge, and an electronically-activated internal wastegate, the GT32 SST had all the bells and whistles, but proved to be a big restriction for the engine. Its dual compressor wheels sat back-to-back on a common shaft, but their small 46mm inducers yielded a power curve that ran out of steam before 3,000 rpm, not to mention that the turbine side was undersized by today’s standards. Once the 6.7L engine is saddled with a programmer, the restrictive GT32 SST can produce shaft speeds in excess of 150,000 rpm. In layman’s terms, the factory turbo is a ticking time bomb once it’s asked to cope with power levels beyond stock.
Eventually, the added fueling provided by a programmer will overspeed the turbo, causing it to self-destruct. This places truck owners in a unique dilemma: spend $1,900 on an OEM replacement unit that might meet the same fate, or invest in a proven alternative. Enter Maryland Performance Diesel’s budget turbo kit for 2011–2014 Fords. The company’s system replaces the factory charger with a time-tested unit from BorgWarner while reusing the factory intercooler piping, and upper and lower intake manifolds. If you’re the owner of a 2011–2014 Super Duty in need of a turbo, then you need to seriously consider this option. For $2,725.95, this system adds unmatched reliability to your truck, along with a noticeable bump in power output.
While the Garrett GT32 SST turbocharger (left) found on the 2011–2014 6.7L Power Stroke is state-of-the-art and a fascinating piece, it’s notorious for overspeeding when pushed hard. Luckily, aftermarket companies like Maryland Performance Diesel (MPD) offer a sound solution: a budget-friendly, bolt-on system that replaces the problematic turbo with a proven one from BorgWarner (right). When it comes to the Garrett GT32 SST facing off against the BorgWarner S366 SX-E, it’s a classic case of complex and intricate vs. simple and proven. Exotic vs. conventional. Contradictory in nearly every way, the GT32 utilizes variable geometry technology while the S366 SX-E is a fixed geometry design. The GT32 features dual cast 46mm compressor wheels vs. the S366 SX-E’s single 66mm forged milled wheel. A ceramic ball-bearing center cartridge resides in the GT32 whereas a journal bearing center section can be found in the S366 SX-E.
The exhaust side of the BorgWarner S366 SX-E offered in MPD’s budget turbo kit features a 73mm turbine wheel (exducer) in a quick-spooling, non-wastegated 0.91 A/R housing, and a T4 turbine inlet flange. While the factory turbo requires both coolant (for cooling) and oil (for lubrication), the S366 SX-E utilizes engine oil for both functions. This is just another way that MPD’s budget kit simplifies the turbocharger system, not to mention that it’s less taxing on the engine coolant.
In order to work in conjunction with the factory hot-side charge air pipe (the tube that spans from the turbo to the intercooler), MPD modifies the compressor housing outlet of the S366 SX-E turbo. And, because this connection point sees the most boost, MPD machines grooves into the edge of the outlet (in addition to the bead on the end). This allows the supplied intercooler boot a rough surface to grab onto and essentially rules out the possibility of blowing an intercooler boot under extreme pressure.
Up-pipes with heavy-duty expansion bellows and the appropriate mounting gaskets are also included in MPD’s budget turbo kit. The up-pipe on the left connects to the passenger side exhaust manifold, while the unit on the right links to the one on the driver side. If seeing up-pipes configured in this unconventional fashion confuses you, you have to remember that the 6.7L Power Stroke utilizes reverse flow cylinder heads. This means the exhaust manifolds reside next to the lifter valley (where the intake manifold would be on a traditional V-8).
Gaining access to the factory turbo is relatively time consuming, with the air intake, radiator hoses, intercooler pipes, air intake valve, and upper and lower intake manifolds all having to be removed before enough room exists to loosen the turbo’s four pedestal bolts. To unbolt the factory up-pipes from the exhaust manifolds, both the passenger and driver side inner fender wells were removed.
After the coolant and oil lines were disconnected from the factory turbo and the wastegate solenoid harness unplugged, the GT32 was finagled under the cowl and off of the engine. Then the pedestal gasket supplied by MPD was installed, followed by the S366 SX-E (shown). To simplify our installation process, MPD bolted the S366 SX-E charger to its respective billet-aluminum turbo pedestal and installed the braided stainless steel oil feed line prior to shipping us the kit.
Once the turbo pedestal bolts were in place, the downpipe was clamped to the turbo’s exhaust housing and the up-pipes were mocked up before being secured in place between the factory exhaust manifolds and the new turbo. Due to limited real estate between the back of the 6.7L engine and the firewall, the driver side up-pipe proved the most time consuming to install.
With the turbo bolted down, the lower intake manifold was reinstalled, followed by the factory hot-side intercooler pipe (albeit equipped with the high-strength silicone boot and T-bolt clamp supplied by MPD). While some aftermarket turbo kits available for the 6.7L Power Stroke do away with the factory upper and lower intake manifold, the MPD kit retains them. By doing this—along with reusing the OEM intercooler pipes—MPD is able to keep the overall cost of its system roughly $1,000 lower than the competition (hence “budget” kit).
Because MPD’s budget turbo kit effectively increases the amount of boost the engine sees, ruling out one of the engine’s weak links is a must. A known flaw on 2011–2016 6.7L Power Strokes is the plastic factory cold-side intercooler pipe, which often blows apart when it’s exposed to elevated boost and heat levels. This intercooler pipe upgrade kit comes from H&S Motorsports, includes a billet-aluminum throttle body assembly, stainless steel replacement pipe, a straight intercooler boot, and a 90-degree intercooler boot that attaches to the factory water-to-air intercooler. It retails for $299.00.
After the OEM composite upper intake manifold was bolted back into place, the factory turbo boost sensor was reconnected, followed by the install of the coolant pipe, air intake, and radiator hoses. With everything buttoned up, the engine was topped off with coolant. Then it was time for one final step—and arguably the most vital part of the entire install.
As you might have already guessed, custom powertrain control module (PCM) tuning is a requirement when you ditch the factory turbo on a 2011+ Power Stroke. With a fixed geometry turbocharger onboard, the engine will see more boost and less drive pressure than before, so the computer basically has to be told (via a custom calibration) that the engine’s boost curve will be different now.
The finished product leaves little indication that the turbo has even been changed. Aside from its looks (or lack thereof), we’re happy to report that with the higher-flowing S366 SX-E turbo in the mix the truck’s midrange and top-end power were noticeably improved. Our seat-of-the-pants impression was legitimized when we learned that aftermarket chassis dyno testing has proven gains of up to 100 hp can be had by swapping to the S366 SX-E. For full disclosure, we’ll also note that due to the S366 SX-E being larger than the factory turbo (as well as a fixed geometry unit), some low-end performance is sacrificed—but the added hint of lag at low rpm is negligible. Don’t forget that the snappiness of the OEM turbocharger is part of the reason it is so prone to failure (i.e., it is overly restrictive).