Adding a High-Flow Turbo, CP3, and 150HP to a 6.7L Power Stroke

Adding a High-Flow Turbo, CP3, and 150HP to a 6.7L Power Stroke

Owners of ’11-’14 6.7L Power Strokes find themselves in a unique predicament when it comes to adding power. These trucks have a horsepower barrier that is two-fold: 1) they’re saddled with the extremely restrictive, dual compressor wheel, Garrett GT32 SST turbo and 2) the factory Bosch CP4 they’re equipped with flows roughly 20 percent less fuel than a comparable CP3. This makes taking advantage of the engine’s piezoelectric injectors—which are said to be capable of supporting 700-rwhp—impossible until both items are addressed. If you only upgrade one, you’re still fighting the other in order to reach your ultimate goal, so it pays to knock both items out at the same time.

With a customer looking to amplify the power of his ‘11 F-350, Flynn’s Shop looked to ditch the stock turbo by way of installing one of Maryland Performance Diesel’s budget SX-E turbo kits. The turnkey system would come with BorgWarner’s new forged milled wheel (FMW) S366 SX-E for considerably more midrange and top-end airflow. On the fuel side of the equation, one of H&S Motorsports’ dual high pressure fuel kits would get the nod, which adds a venerable Bosch CP3 on top of the CP4. With the ability to maintain rail pressure and benefit from vastly increased airflow, somewhere in the neighborhood of 150 to 200 hp can be gained with this type of upgrade. Read on to see what it takes to overcome your ’11-’14 6.7L Power Stroke’s horsepower hurdle. DW

BorgWarner’s S366 SX-E turbocharger is impressive to say the least. The 66mm forged milled wheel compressor is said to flow 94 pounds per minute (approximately 1,340 cfm), and the center cartridge comes with a 360-degree thrust bearing assembly right out of the box. Other features include the proven 73mm/80mm turbine wheel, a T4 flange, and a 0.91 A/R exhaust housing. MPD modifies the compressor housing outlet to accommodate the 6.7L Power Stroke’s factory hot-side intercooler pipe.
With the air intake, intercooler pipes, air intake valve, upper and lower intake manifold, up-pipes, and the factory turbo removed, the guys at Flynn’s turned their attention to the installation of the dual high pressure fuel kit. Installing the fuel system before the new turbo helped avoid any clearance or routing issues later on in the day.
As you can see here, the S366 SX-E turbo and factory Garrett GT32 SST are 100 percent polar opposites. The factory variable geometry turbo utilizes two 46mm inducer cast compressor wheels, is wastegated, and utilizes coolant for additional cooling. The fixed geometry SX-E on the other hand features a single, forged milled wheel technology compressor, has no wastegate, and does not have provisions for circulating coolant (only oil). Last but certainly not least, the stock turbo can only support 450 to 500-rwhp, while the S366 SX-E can support 650 to 700-rwhp.
The dual high pressure fuel kit from H&S Motorsports adds a brand new, OEM-spec Bosch CP3 pump on top of the factory CP4 in order to maintain rail pressure while demanding more duration from the stock injectors. The system mounts a 6.7L-based Cummins CP3 where the second alternator would reside on dual alternator Super Duty’s, gets belt driven, and effectively shares the work load with the stock CP4 (making its service life much easier). H&S recommends that an upgraded fuel supply pressure system be utilized with its dual pump kit, although it isn’t mandatory (some factory lift pumps can keep up, while others can’t).
After capping off the vacuum line for the factory turbo’s wastegate with the supplied plug from MPD, the serpentine belt was removed, followed by these two idler pulleys. One idler would be reused later on (in conjunction with the supplied idler spacer and 3/8-inch bolt) once the CP3 was in place. It’s important to note that, while H&S supplies a new serpentine belt with its high pressure fuel kit, it is a single sided belt (ribs only exist on the pulley side), which is found on later 6.7L engines. Because we were working on an earlier engine (‘11), the double-sided belt had to be reused.
For adequate CP3 pulley clearance, the engine idler post (protrusion) on the factory fan hub had to be modified. Some opt to notch out a small portion of the post, but the techs at Flynn’s removed it completely (for ultimate clearance, and peace of mind).
From there, the factory passenger side front fuel rail plug was removed (using a 10mm, 12-point torx socket) and replaced with the supplied fuel rail feed fitting, which was torqued to 74 ft-lb. This fitting feeds fuel from the CP3 into the passenger side rail.
In order to tie the supplied injection pump harness into the factory injection system’s, the outer tabs of the gray locking connector on the factory CP4 harness had to be ground off. Once that was done, the supplied cheater harness plugged right in.
Next, the CP3 was bolted to the pump mounting bracket using the three 5/16-inch bolts supplied by H&S (which were torqued to 20 ft-lb), and reusing one of the factory fan hub bolts, complete with the included lateral support spacer. All told, the bracket features provisions to mount the CP3, attach the fan speed sensor wire harness, and reuse one of the engine idler pulleys. However, the mounting bolts were left loose until the high pressure fuel line was connected to the CP3.
The beauty of adding a second injection pump to any engine is that it allows each pump to share the workload. While capable of more, at full tilt both pumps will be contributing roughly 14,000 to 15,000 psi in this system. The beauty of adding a CP3 to maintain rail pressure is that, should the owner want to pursue even more horsepower later on, a 10mm or even 12mm stroker pump can be used in its place to support much larger nozzles.
Prior to installing the supplied high pressure fuel feed line between the CP3 and passenger side fuel rail, compressed air was sent through it to make sure it was free of any debris. From there, each end was coated with white lithium grease (for an optimum seal), and the line was installed but its nut not yet fully tightened.
Once the CP3 mounting bracket bolts were torqued (20 ft-lb), the serpentine belt was reinstalled and the CP3 nut was torqued to 74 ft-lb. After that, the aforementioned high pressure feed line nuts were torqued to 38 to 48 ft-lb.
Moving on, the supplied 3/8-inch fuel feed and return fittings were threaded into the CP3, followed by the corresponding 3/8-inch fuel hose being connected, routed over to the factory fuel filter housing, and cut to length. At this time, the cheater harness was plugged into the CP3’s fuel pressure regulator (i.e. MPROP) and the rest of the wiring was zip-tied up so as not to touch or rub any part of the lower intake manifold, coolant crossover, or CP4 (to avoid grounding out issues later on down the road).
H&S includes a straightforward fuel filter conversion system with its dual high pressure pump kit, which replaces the factory fuel filter housing assembly in favor of a 4-port, CNC-machined filter base complete with a Baldwin fuel filter (PN BF7967). Note that the guys at Flynn’s purposely left off the fittings that thread into the passenger side of the filter base (which feed the CP4 and CP3) until the turbo and intercooler plumbing was installed, just in case any clearance issues surfaced.
For convenience, MPD shipped the S366 SX-E already bolted to the pedestal, and with the oil feed line pre-attached. All the guys at Flynn’s had to do was install the supplied turbo pedestal gasket, followed by the turbo assembly.
With the turbo pedestal bolts tight, the downpipe was connected to the turbo’s exhaust housing outlet and the supplied up-pipes were bolted on. The driver side up-pipe was definitely the more time consuming of the two assemblies to install.
After the lower intake manifold was reinstalled, the factory hot-side intercooler pipe was attached to the turbo and water-to-air intercooler. MPD’s turbo kit includes a high-strength silicone boot and stainless steel T-bolt clamp for this connection point.
Because the MPD budget kit retains the factory intercooler pipes, it doesn’t hurt to do everything you can to ensure they stay put when exposed to higher boost levels. For added insurance against a blown intercooler boot, the guys at Flynn’s welded a bead onto the factory hot-side pipe. So far, the added grip has had zero problems holding up to 40-plus psi of boost.
Knowing that the factory (plastic) cold side intercooler pipe is known to blow apart, a cosmetically appealing, permanent fix was installed. Called H&S Motorsports’ intercooler pipe upgrade kit, it entails a bead-rolled, stainless steel cold side replacement pipe, a new CNC-machined, billet-aluminum air intake valve, and comes with two T-bolt clamps and all necessary hardware.
As previously mentioned, the factory upper intake manifold is retained with MPD’s budget turbo kit, and it was next on the install list. After that the engine’s boost sensor was reconnected, followed by the engine cooling system’s coolant pipe.
Reinstalling the final component, the customer’s existing S&B air intake, was the last bolt-on item to grace the engine. Once it was in place, the ignition was cycled to the “On” position six separate times to get the fuel system primed and ready for startup.
Prior to firing up the truck, both the secondary and primary cooling systems were filled. The secondary cooling system (shown) serves the transmission, EGR system, and water-to-air intercooler on 6.7L Power Strokes, while the primary system is solely devoted to engine cooling.
Custom PCM tuning is a must with a fixed geometry turbo installed on a 6.7L Power Stroke. Because of the back pressure reduction, the volumetric efficiency vs. rpm vs. boost is higher with a fixed geometry turbo in the mix, so the computer essentially had to be told that the engine’s boost curve would be different. For this build, this task was left to the experts at Gearhead Automotive Performance, as well as the TCM (transmission control module) calibrating.
Once the transmission had time to learn the new shift strategy, the truck was subjected to a few hard test runs. In comparison with the quick-lighting stock charger, the S366 SX-E did sacrifice a little low-end response, which we expected. However, there is no comparison whatsoever to how well the truck runs in the midrange and top end. It pulls incredibly strong to 3,500 rpm (vs. falling on its face at 3,000 rpm with the stock turbo). We also observed 41-to-43 psi of boost, cooler EGT, and—thanks to the CP3 over CP4 combination—a steady 29,000 psi worth of rail pressure.


Flynn’s Shop

H&S Motorsports

Maryland Performance Diesel

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