There are many ways to efficiently gain more power with a diesel engine. Choosing the correct setup for doing so depends on the desired end result.
For enthusiasts looking for a mild bump in performance, such upgrades as a cold-air intake and programmer might be all that is needed. Folks who want a bit more power may add a mild turbocharger and larger injectors. When a lot more horsepower is desired, multiple turbochargers are added, along with injectors and lift and high-pressure injection pumps. An oil-burner’s performance really depends on the amount of money one is willing to spend.
Most diesel-truck owners want middle-of-the-road performance. They want more power than a stock engine provides for a bit more get up and go on the highway and while towing but do not want to lose the truck’s reliability and driveability. Finding the right balance is important.
| This is the stock 6.6L Duramax LML engine in the ’15 Chevrolet Silverado 2500HD that is receiving Deviant Race Parts’ compound-turbocharger upgrade.
A compound-turbocharger system is ideal for increasing a diesel’s power. The abundance of air provided by two turbos works well at keeping an engine’s internal temperature down, allowing for more efficient combustion. A compound system that’s paired with good ECM tuning and proper fuel delivery can provide a performance increase across the entire rpm range and help lower EGT. Deviant Race Parts created a bolt-on compound-turbo kit for 6.6L Duramax LML-powered GM pickups just for this reason.
The Deviant Race Parts LML Duramax Compound Kit is highlighted by a BorgWarner S475 T-6 turbocharger that forces air into the LML’s stock unit. Installing a second ’charger that doesn’t require major engine modication is one of the keys to keeping a truck reliable and driveable. Deviant’s kit is designed for easy installation and includes all the pipes, hoses, fittings, and brackets needed. Optional turbos are available, and with the right combination of fuel and tuning, the setup is capable of supporting up to 750 hp.
We took a trip to Deviant Race Parts in Hayden, Idaho, and watched Chris Rosscup install a kit on a 6.6L Duramax LML–powered ’15 Chevrolet Silverado 2500HD. For this application, the S475 was fitted with a smaller 1.15 AR turbine to provide faster spooling and to better match the 10mm CP3 injection pump that was previously installed. To manage the hopped-up engine, a switchable ECM tune by MotorOps was downloaded.
The new power-adder combination is said to produce around 650 hp. It will also lower EGT and distribute power evenly across the entire rpm range. Other cool benefits of the DRP compound-turbo system are that it retains the stock exhaust brake and emits virtually no smoke from the tailpipe.
Follow along through the photos and captions as we watch Chris masterfully install Deviant’s system.
Chris Rosscup strips the engine of unnecessary components and makes room for the Deviant Race Parts 6.6.L Duramax LML Compound Turbo Kit. While some of the sensors in the stock air-intake system are reused, the airbox, coolant tank, and downpipe can be discarded. The inner fenderwell on the passenger side is also removed for easier access. Some wiring is moved out of the way.
| With the unnecessary components removed, Chris starts installing the system by bolting the turbo mount onto the side of the engine. He grinds off the bracket’s powdercoating to guarantee a solid connection for electrical grounds that are secured by the bolts.
| Deviant Race Part Compound Turbocharger Kit Engine Block Turbo Mount
| The turbo’s oil-drain gasket is installed on the mount with a bead of silicone to hold it in place and eliminate the chance of a leak occurring.
| With the gasket in place, the turbo is lowered onto the mounting bracket and bolted into position.
| This AN-4 fitting is installed in the turbo’s oil-feed port. The braided-steel line is then attached to the fitting before it is routed to the AN-4 fitting in the oil galley at the front of the engine. This is the oil that lubricates the turbo.
| The hot pipe between the stock turbo in the valley and the new BorgWarner ’charger is connected to each turbo using the original clamp and 3/8-inch bolts (and gasket). The larger unit’s turbine housing may need to be loosened for proper alignment.
| The MAP sensor is installed on the Y-bridge before it is bolted on the engine.
| Deviant Race Part Compound Turbocharger Kit Y Bridge Installed
| Before the charge pipe is installed between the turbos, the supplied O-ring is set in place with a dab of silicone to secure it. Chris positions the pipe and attaches it using the stock clamp on the small end and a new clamp for the large end.
| Deviant Race Part Compound Turbocharger Kit Charge Pipe Engine
| Air-conditioning lines may need to be tweaked slightly for intercooler pipe installation. The tube is secured using two 3-inch boots and clamps.
| The wiring harness is unclipped from the firewall and the shock tower and repositioned out of the way.
| Chris removed the starter to provide enough room to drill and tap the upper oil pan with a 3/8-inch NPT. (It is suggested the oil pan be full when drilling and tapping so any metal shavings are flushed out of the pan.) The hole needs to be properly located so the 45-degree AN-10 fitting can be screwed into position without hitting the block and the starter reinstalled without any problem. The braided-steel line is routed from the pan up to the oil-return port on the turbo.
| Deviant Race Part Compound Turbocharger Kit Turbo Mount Oil Return
| This ground strap is unbolted from the body mount and moved out of the way. It is reattached to the airbox mount later.
| To make room for the new downpipe, one of the firewall studs is removed. This can be done either with a chisel blade on an air hammer or with a cutoff wheel. Chris uses the air hammer.
The upper half of the new downpipe is installed on the back of the big turbo with a 5-inch V-band clamp. The lower section is then positioned using a 4-inch V-band clamp. The clamps are left loose until the entire downpipe is properly positioned.
| The front section of the exhaust is measured and cut to the correct length and connected to the downpipe using a band clamp.
| Deviant Race Part Compound Turbocharger Kit Downpipe Exhaust
| A battery cable extension is bolted to the stock wire that runs along the firewall. Heat shrink is used to protect the connection from the elements.
| Electrical tape holding power wires for the glow plugs and gird heater needs to be cut off to allow the wires to be separated. The grid-heater wire is then removed from the fuse panel.
The battery tray is positioned so the cell does not interfere with anything. Two 3/8-inch holes are drilled through the existing airbox mount. A bar and two bolts are used to sandwich the tray to the mount.
| Chris uses a body saw to trim the fuse panel to clear the new battery location. A 7/16-inch hole is drilled into the side of the panel and secured in position with the supplied L-bracket. The battery cable is then attached to the fuse panel.
| Deviant Race Part Compound Turbocharger Kit Fuse Panel Mounted
| Stock studs and washer nuts secure the coolant tank to the fender next to the turbo.
| Barbed fittings are inserted in the ends of the coolant lines. The included 90-degree coolant hose is cut to length and attached to the preexisting hose using the barbed fitting. A piece of smaller blue hose extends the second line to the tank.
| Deviant Race Part Compound Turbocharger Kit Coolant Tank Hoses Attached
| The plug for the stock coolant-level sensor is cut off, and the wires are then connected to the level switch on the tank.
| MAF sensors are installed in the intake pipe before the pipe is attached to the turbo. Wires for the two sensors’ plugs must be cut apart, enabling the plugs to reach the relocated sensors. The intake pipe is secured with two 5-inch clamps and a boot.
| The air filter is the last hard part that is installed. The only other tasks to complete on the engine are refilling the coolant, checking fluids, and reconnecting the batteries.
| With the truck back together, Chris uses his laptop and an EFILive programmer to install the MotorOps switchable ECM tune created for this compound-turbo application.
| Deviant Race Part Compound Turbocharger Kit Engine Bay Turbo Installed