Compounding Interest - Diesel World

How to Make Your 6.7L Cummins a Worthwhile Investment

Bolt-on compound turbo systems are all the rage these days. In fact, they have been for years, and for good reason. No other modification allows you to add substantial horsepower yet retain factory-like drivability. With a correctly sized turbo arrangement, bottom end response and low-end torque improves, midrange power is strong, and the atmospheric charger allows big power to be made up top. If done right, you can drive daily, tow, and go racing all with the same setup. No matter what you use your truck for, it will do it better with a well-designed compound turbo system under the hood.


The Fleece Performance Cummins Compact Compounds system for 6.7L Cummins-powered Rams is proof that not all compound turbo kits are created equal. The fact that it allows you to retain the factory downpipe makes this system extremely appealing to the truck owner who hasn’t added a ton of power yet is in the market for a turbo upgrade. As for the enthusiast who is chasing horsepower, with the right supporting mods this kit will support 850 hp.


1 A BorgWarner-based S400 serves as the atmosphere (lowpressure) turbo. Assembled by Fleece, it features a high-flow billet compressor wheel with a 75mm inducer.


2 A S362 SX-E from BorgWarner bolts to the exhaust manifold. The non-wastegated, T4 flange charger features a cast 62mm (inducer) compressor wheel and BorgWarner’s 73mm (exducer) turbine wheel. In terms of exhaust flow, the 73mm turbine is a nice upgrade over the old 68mm wheel.


3 While the whole S362 over S475 thing has been done before, it’s never been done quite like this. Thanks to Fleece adding its own V-band turbine outlet to the S475, the factory downpipe can be retained. You read that correctly: This system will bolt right up to the stock exhaust system. As for the S362, Fleece modifies the compressor housing outlet and inlet to incorporate a V-band clamp.


4 Any time compound turbos are being added to a Cummins, the A/C system has to be reworked if you plan to keep it. Once the passenger side battery, battery tray, inner fender well, serpentine belt, fan, fan shroud, and coolant reservoir were off the truck, the guys at Fleece were able to start removing the factory A/C lines. To simplify the process of installing compound turbo systems, Fleece offers an A/C line reroute kit for 2013 to 2016 Rams. Here you can see the new fittings being installed in the A/C compressor.


5 The biggest thing that Fleece’s A/C line reroute kit does is get rid of the hard lines and replace them with high-quality Parker A/C hose, which is obviously easier to route around the turbochargers and all of their respective piping. Fleece also machines all of the adaptor fittings in-house to make the custom set of A/C lines fit and function like the factory equipment.


6 As far as the work near the engine is concerned, Fleece recommends the lower (atmosphere) turbo bracket be installed first. Because the passenger side motor mount bolts are used to mount the turbo bracket, they have to be removed (and then left loose until the entire kit has been installed), followed by the factory heat shield (shown) that’s riveted on. We’ll note that removal of the exhaust manifold makes it much easier to access the heat shield rivets.


7 According to Fleece, the best way to install the lower turbo mounting bracket is by loosening the front two passenger side motor mount bolts and then removing one of the rear motor mount bolts at the same time. Once the rear bolt was out, the corresponding bolt hole on the lower turbo mount was lined up. After finger tightening the bolt in place, the front motor mount bolt was removed, the lower turbo mount positioned into place over its respective bolt hole, and the bolt was reinstalled. The motor mount bolts were then re-torqued to the factory specification.


8 Prior to installing the atmosphere turbo, the front passenger side freeze plug was removed from the block. This port allows the oil from the manifold charger (S362 SX-E) to drain back into the block.


9 Next, a T4 Steed Speed exhaust manifold was bolted on. In this particular truck’s case, one of Fleece’s 2nd-Gen turbo swap kits was previously installed, so the Steed Speed manifold was simply being reused. Customers have the option of choosing from a Steed Speed manifold, a cast ATS manifold, or supplying their own manifold when ordering the Cummins Compact Compounds kit. We’ll note that it’s a good idea to install each manifold gasket and use the bolts to hold them in place before attempting to install the manifold (as shown).


10 Once they were snugged up by hand, the exhaust manifold bolts were taken up to 35 ft-lb via torque wrench. Also notice the fasteners in the head. Before the engine could be subjected to elevated boost levels, it was fitted with ARP head studs.


11 Then it was time to lower the Billet S475 into place on the lower turbo mounting bracket, followed by installing the oil feed line. Since it runs along the side of the block, the -6 AN oil feed line for the S475 is thermal wrapped to reflect as much radiant heat as possible.


12 One of Fleece’s coolant bypass kits graced the engine as well (arrow). The bypass-style system uses a secondary thermostat that operates based on temperature (vs. pressure), which solves the pressure issues modified Cummins mills are known for having at higher horsepower levels. It also guarantees that consistent coolant temps exist across all cylinders. Out for several years now, the company’s coolant bypass kit has become a big hit in the aftermarket.


13 The hot pipe, which was heat wrapped to keep radiant heat to a minimum, was installed next. It’s important to note that nothing should be tightened completely (other than the exhaust manifold bolts) until the entire compound kit is in place. Notice the oil drain line for the S362 laying across the S475.


14 With the T4 turbo gasket in place, the S362 was positioned on the exhaust manifold studs. Once its respective nuts were tightened, the oil drain and feed lines were hooked up.


15 Using a little muscle, the 45-degree, 5-inch rubber intake boot was finagled onto the atmosphere turbo (arrow), along with its supplied T-bolt clamp. It’s important that this boot is clocked correctly or the intake tube won’t clear the oil filter once it’s time to install it.


16 With the factory battery tray reinstalled, things started to come together in the engine bay. It’s best to install the battery tray before hooking up the intermediate pipe, air intake tube, and hot-side intercooler tube, just in case any clearance issues arise.


17 A fabricated aluminum coolant overflow reservoir is supplied with the kit and replaces the bulky, plastic unit. It mounts in the passenger side rear corner under the hood, and is secured to the back of the passenger side battery tray.


18 Next, the intermediate pipe was installed (the tube that links the intake side of the S475 to the S362). With solid connection points (Vband clamps) being used throughout the system, the kit feels solid, not to mention that blown boot scenarios won’t be a problem.


19 As for the hot-side intercooler pipe, a bead is rolled on the intercooler side to keep the boot from sliding under big boost. A V-band flange is used on the turbo side (where the hot-side pipe attaches to the compressor outlet of the S362).


20 After a bit of finagling, the 5-inch air intake tube (also known as a “Man- Take”) slid into the aforementioned 45- degree rubber boot previously installed on the atmosphere turbo. It’s a tight fit, but everything has clearance once installed.


21 The final touch was adding the massive, vertically mounted air filter to the intake tube. Thanks to the A/C line reroute kit, no clearance issues exist despite the air filter’s tight quarters.


22 Prior to the Cummins Compact Compounds being installed, the 6.7L was graced with 100% over injectors and Fleece’s new dual pump kit. Unique to the Fleece dual pump kit is that no CP3 controller is necessary, as Fleece can control the second pump via EFI Live tuning.


23 Designed, developed, and produced to maximize the performance of trucks making between 500 and 850 hp, this kit appeals to a wide range of customers. Whether you’re building the ultimate tow rig with little (or no) fuel system upgrades, a hot-running daily driver, or an 11-second screamer, this pair of turbos can get you where you want to be.

Fleece Performance Engineering has been in the turbo game for more than a decade, so when we heard they were developing a new compound turbo package for the 6.7L Cummins we leapt at the chance to see it installed on a ’16 Ram. To rule out reliability issues, as well as add considerable horsepower, the system scraps the factory variable geometry Holset HE351VE on the manifold in favor of an S362 SX-E from BorgWarner, and one of Fleece’s billet S475 chargers serves as the low-pressure unit. With the right supporting mods, this system can be pushed to the 850hp mark, but it’s also right at home in trucks with stock injectors. Warning: Further reading may have you spontaneously reaching for your credit card… DW