Ford’s early 6.7L Power Stroke used Garrett’s gated dual-compressor VNT with two compressor inlets and a double-sided compressor wheel on one shaft. The idea was straightforward: keep the turbo responsive at low shaft speed and low mass flow, then carry enough airflow and density at higher boost and load. The problem is the mechanical layout. With so much compressor mass hanging out on the shaft, the assembly carries a lot of leverage and load in a very demanding environment. It was an ambitious way to widen the operating range, but it also helps explain why this turbo was short-lived and why Ford moved away from the dual-wheel arrangement.
The video examines Garrett's dual-boost VNT, a gated dual-compressor turbocharger built on a common shaft. Ford used this design on the 2011 through 2014 Power Stroke. The focus is on the compressor side of the assembly, where the unusual architecture becomes immediately visible.
Unlike a conventional turbocharger with a single centered compressor inlet, this unit has two separate inlets feeding the compressor system. One is the familiar on-center inlet at the front of the turbocharger. The second routes air toward what would normally be the backplate area behind the compressor wheel.
That second passage is the key visual clue that this is not a conventional single-face compressor arrangement.
With the compressor housing removed, the internal layout becomes clearer. On the common shaft sits a compressor wheel with two working faces. Each face carries its own set of blades, creating a dual-sided compressor arrangement on a single rotating assembly.
The visible blade count appears similar between the two sides, although the rear side is more difficult to inspect directly except through the cutaway shown in the video.
The purpose of the configuration was to broaden the turbocharger's operating range. It was intended to operate from low boost pressure, low shaft speed, and low mass flow through high boost pressure, high air density, and high mass flow.
The goal was to maintain useful compressor performance across a wide range of engine operating conditions rather than optimizing the compressor for a narrow portion of the operating envelope.
One of the notable engineering characteristics visible in the cutaway is the amount of rotating mass positioned outward on the shaft. The compressor assembly places substantial mass away from the shaft support, creating an unusual mechanical arrangement compared with a more conventional compressor wheel.
That packaging highlights the challenge of maintaining shaft stability and durability while achieving the desired compressor performance.
The architecture suggests a significant development effort. Combining two compressor inlets, a dual-face compressor wheel, variable turbine geometry, and a broad intended operating range would have required considerable engineering, testing, validation, tooling, and manufacturing development.
The speaker emphasizes just how much time and money likely went into developing and debugging such an unconventional turbocharger.
Despite its complexity, the design had a relatively short production life. Ford used the Garrett dual-compressor turbocharger on the 2011 through 2014 6.7L Power Stroke before moving to a different turbocharger configuration.
That short run makes the design particularly interesting: it represents an unusually sophisticated approach to expanding turbocharger operating range that appeared on production trucks for only a few model years.
