When rumors began circulating last year on the Internet that Ford was replacing its 6.0L Power Stroke with a new 6.4L engine, the buzz wasn't over the new piezo injectors or the common-rail injection-it was the dual turbos.
While it's not technically accurate to call them twin turbos, the new 6.4L Power Stroke uses a series-sequential turbo system built by BorgWarner in North Carolina. These two turbochargers are packaged together as one air-management system to feed the 350hp Power Stroke and help International meet the new '07 diesel emissions standards. This exotic turbo arrangement is by far the most impressive induction system available on a light-truck diesel engine. So when Diesel Power got an invitation to see how they're built, we jumped at the chance.
BorgWarner's Asheville, North Carolina, facility houses a fully automated assembly line to build the new 6.4L Power Stroke's dual-turbo system. Mechanized systems like this compressor-housing dispenser, dozens of robots, and three shifts of workers make it possible for this plant to produce a complete 6.4L turbo package, every minute, 24 hours a day. | 
BorgWarner draws from its global parts supply chain to bring the new 6.4L turbo pieces together. Here, a shipment of turbine wheels for the 6.4L's low-pressure turbo arrives in crates. | 
The turbine wheels are then joined to shafts by a friction-welding process. Then the shafts are precision machined for the journal bearings and compressor wheels. |
From there, racks of the new turbine wheel and shaft assemblies are loaded into computerized machines that clean, deburr, and balance the assemblies to ensure they can withstand the high speeds they'll see in real-world use. | 
Not only does the 6.4L feature two stages of BorgWarner turbocharging, but one of those stages (the high-pressure side) also features a variable-turbine geometry (VTG) housing. Depending on the application, BorgWarner's VTG turbos are assembled by hand or robot. | 
For the high-volume 6.4L turbo system, an automated robot constructs each VTG vane assembly on this multiple-process turret. Machines like this one combine the manufacturing and quality-control duties into a single stage and reject faulty subassemblies before they make it into the finished product. |
BorgWarner Turbo Systems took us inside its North American commercial vehicle turbochargers development center. We met with the engineers, signed a confidentiality agreement (so we can't tell you about all the cool stuff we saw until BorgWarner gives us the OK), and we got to tour the entire facility. Rest assured, these guys know turbos. Every corner of the facility was packed with exotic technology and enthusiastic people who help make the world-class chargers many of us are running in our own diesel-powered vehicles. This month, we wanted to give you a peek behind the curtain to see how the 6.4L's turbos are built. In the coming months, we'll show you some of BorgWarner's other technology and how the company's OEM expertise is making its way into your diesel-powered projects.