Cummins Compound Turbos

Cummins Compound Turbos: Street and Tow-Worthy 700+ HP Combo

If you own a 2003-2007 Dodge with the 5.9L Cummins, it’s likely that you’re already well aware of the massive number of aftermarket options available to make more power. For most owners, being able to make clean, usable horsepower is the goal. Upgrades that leave you with smoke belching from the tailpipe or throttle delay while waiting for the big turbos to spool up are not for the street. Most owners want to see a responsive, drivable engine with extra horsepower that can be used every day, whether towing a trailer or not.

Cummins owners looking for more power than you get from a simple intake, exhaust and tuner might want to consider taking the leap into a compound turbo system. This upgrade doesn’t have to be so scary. If your drivetrain is tough enough to handle the extra output, this single upgrade can push your truck to new power highs. The compound turbo system from Deviant Race Parts (DRP) of Hayden, Idaho, is one such system and we’ll show it to you here. This system can turn the average run of the mill truck into a trailer-towing monster with plenty of air to support 700+ horsepower.

DRP has been manufacturing diesel performance products since 2009 and has recently jumped into the compound turbo scene. They go the extra mile and do their compound kit development in house. Countless hours of test fitting help them to produce clean, simple and easy to install systems for both Cummins and Duramax applications.

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The DRP kit used for this article places a BorgWarner S475 unit from High Tech Turbo of Salt Lake City, Utah, directly over the top of the stock-style turbo. It’s mounted low in the chassis on a stock-style exhaust manifold. By building the kit this way, DRP can limit the out of pocket expense and labor time to the end user, as most of the stock components remain under the hood.

The factory-style air intake and downpipe are all that really need to be removed. While some factory components need to be moved or adjusted under the hood, the kit will bolt right into place. Unless you’re quite comfortable with deep engine work, it’s recommended that you have the work done by a qualified shop or experienced mechanic. The upgrade is rather time and labor intensive. We followed along with a camera as DRP did this upgrade in their shop. DW

1. The new BorgWarner S475 from High Tech Turbo is a common low-pressure turbo for daily-driven trucks, and should be more than enough air to support 700 hp in the 2003-2007 5.9L application.

2. The intermediate pipe supplied in the DRP Compound system clamps directly onto the stock turbo, and routes exhaust gases through a tight mandrel-bent 180 to the new S475’s turbine inlet flange. It comes pre-wrapped with header wrap, which serves two purposes: keeping nearby components safe from heat and retaining the exhaust gas heat inside the pipe to drive that big turbine harder.

3. The stock-style turbo and manifold are retained, so there’s no reason to remove them from the vehicle.

4. On the 2003-2007 5.9L trucks, the downpipe is connected to a cast elbow that’s clamped to the turbine housing of the HE351 turbocharger. Both the downpipe and the cast elbow will need to be removed for this install. The V-band clamps just need to be loosened, but thanks to the heat cycles they’ve undergone, they can be a bit stubborn to break loose.

5. The Cummins engine block has two locations for oil drains; the rear port is used by the stock turbocharger, but a port towards the front of the engine is unused. This port has a small freeze plug that will need to be removed by drilling a small hole in the center and threading a screw into it to give you something to leverage it out with. Once removed, the supplied oil drain fitting can be tapped into place.

6. The next step is to install the new turbocharger’s center section into the turbine housing and bolt it down to the support bracket, making sure to keep the oil drain gasket centered under the turbo for proper sealing. The 90-degree boot and small metal V-band pipe can be connected to the stock turbo inlet. This short junction will feed air from the S475’s compressor outlet to the high-pressure compressor before being fed through the intercooler to the engine.

7. With the intermediate pipe and downpipe (also wrapped with header heat tape) slid into place, the S475’s support bracket can be bolted into place. You’ll notice the oil drain location has been drilled through and an AN-style bung welded to the bottom side to accept the drain hose.

8. The final step of the project is installing the intake system. The large 5-in. diameter pipe and big aFe oiled filter will flow plenty of air to the big turbo.

[divider]TWIN TURBO UPGRADE RESULTS[/divider]

In addition to the DRP compound turbo kit, this truck was also outfitted with 90-hp injectors and a modified CP3 pump. First, it was driven for a few days to make sure there were no leaks or running quirks that needed to be worked out. After a smooth shakedown period, the new upgrades were put to the test. Running a mild Level 2 program on the Edge Evolution tuner, the truck felt very responsive with good low-end spool-up and healthy top-end power. Tailpipe smoke output was lower than expected and the EGT stayed well below the known “too hot” threshold.

After about 50 miles of driving, the test truck was strapped to the dyno at Edge Products. This is where it was initially tested after the HT Turbo Airflow for Tow package was installed a while back (see the March 2014 issue of Diesel World for more on that). Running the truck through the same testing conditions—like dyno load, engine rpm sweep, etc.—back to back, allowed before and after comparisons to be judged fairly accurately.

On the Level 1 software setting and with the new parts installed, the truck managed to squeeze out a very healthy 523 hp and 1,034 lb.-ft. of torque. Boost peaked at 39.9 psi and EGT was a nice and safe 1,162 degrees. At just 1,162 degrees with this milled tune, the torque curve should make this truck a monster with a trailer behind it. With a strong transmission and drivetrain backing the engine, this combination of parts should do just about everything you could ask of it, whether it’s dragging a 10,000-lb. tractor around town or keeping the big 40-ft. fifth-wheel toy hauler rolling down the highway.

Bumping the Evolution tuner up to its hottest Level 4 tune, we saw 792 hp and 1,483 lb.-ft. as the final peak numbers. Previous testing with the stock injectors and modified stock turbo only had produced 549 hp and 1,178 lb.-ft. on Level 4 tuning. So the addition of 90-hp DRP injectors, BD Diesel’s high-power CP3 and the DRP Compound turbo system resulted in an additional 243 horsepower and 305 lb.-ft. of torque.

The most incredible stats from this build-up however are the exhaust gas temperatures (EGT). In mostly stock trim—Airaid intake and 4-in. MBRP exhaust only—the truck made 320 hp and 601 lb.-ft. at 1,333-degree EGT. Now, with the array of aftermarket bolt-ons, horsepower and torque have more than doubled (+472 hp/882 lb.-ft.), but peak EGT has increased by only 120 degrees. Reaching nearly 800 hp at a peak output, and with EGT at just 1,450 degrees on the dyno, this combination of parts works like a dream. This just proves that with good tuning and the right parts, the 5.9L Cummins can put out some amazing power numbers, all while keeping good street and towing manners.