The Sum of All Parts

We recently bought a new 2006 Dodge Ram Mega Cab. It's spacious and comfortable, and the Cummins turbodiesel is powerful, but it could always use more. Fortunately, most of today's diesel engines can be modified to significantly increase horsepower and torque, and we were tempted to add some performance items to this one. But we had to decide where to start and how to spend the money. Also key was knowing that the money we invested would actually improve the truck's performance. We wanted to improve an already good powertrain without blowing our hard-earned cash.

The only way to tell whether we made the right choices was to add a sampling of performance products in a logical order, run the truck on a dyno between each modification, and examine the numbers. For this test, we chose experienced companies with products that fit our needs. The Ram was to be a daily driver, not a dragster--its manners had to remain intact as well as its long-term reliability.For all modifications and subsequent tests, a calibrated Mustang dynamometer was used. Note that all dynamometers don't read the same. Factors such as altitude, ambient temperature, humidity, and the specific programs being used on a given dyno on any given day have to be considered. The actual numbers are just that: numbers to be compared with other numbers derived from similar conditions. Your results may vary.

Corsa's Reflective Sound Cancellation technology allows Corsa to tune out the undesirable low frequencies that cause droning.

After discussing the project with several diesel experts, we started with the air intake and exhaust. While we didn't expect huge gains from these components, a diesel engine needs to breathe, so the functions of these items would come into play later. A baseline test came first: on the dyno, our stock truck showed 265 horsepower and 505.8 pound-feet of torque, as we expected.

In phase one, we installed a Corsa Performance exhaust, a straight-through, nonrestrictive system. Using 304 stainless-steel four-inch-diameter mandrel-bent tubes, it's said to provide a 47-percent gain in exhaust flow over stock. That means lower exhaust gas temperatures (EGTs) and improved horsepower and torque. But Corsa's Reflective Sound Cancellation technology, which allows the company to tune out the undesirable low-frequency sounds that cause droning at speed, is a huge plus.

S&B's cold-air intake kit claims to flow 40.2 percent more air than stock. We like that the custom airbox has a clear inspection window.

After installing the exhaust and hydroformed four-inch oval stainless-steel tip, the Ram went onto the dyno. Horsepower increased to 268.9 and torque to 513.8. That's not a huge difference, but the Ram's got a great deep throaty sound when you tromp on it. The complete cat-back kit lists for $953.99.

Next came an S&B cold-air intake kit that's said to flow 40.2 percent more air than the factory system. We like the easy installation, huge eight-layer gauze/mesh filter, and custom airbox. It even has an inspection window. With this system, horsepower increased to 269.1 and torque was measured at 513. Again, that's not a huge difference, but the superior airflow of the S&B Filter will be essential later on, especially with lower EGTs. The performance intake kit lists for $194.61.

The ATS ARC Flow intake creates a smooth path for the air. More air means more oxygen, and that means more efficient combustion.

As the cooled air exits the intercooler, the next restriction in the factory system is the intake manifold. By installing the ATS ARC Flow intake, a smoother path for the air to follow was created. More air means more oxygen, and that means more efficient combustion. The ARC Flow allows the air to expand at a rate that doesn't create turbulence as the air is fed into the cylinder heads. The ARC Flow also comes pre-tapped for accessories, including water injection and boost gauge. A turn on the dyno demonstrated horsepower up to 275.8 and torque at 526. The ATS ARC Flow intake goes for $396.

The engine was breathing better, but the improvements were still nothing to jump up and down about. Ken (our expert at Ken Imler Diesel Performance) pointed out that while the dyno numbers weren't huge, intake and exhaust modifications typically produce as much as 20 horsepower under a real load, like hauling a heavy trailer up a steep grade, again because both will significantly reduce the EGT.

Digging still deeper in our pockets, we exchanged the factory turbo and exhaust manifold for the ATS Aurora 2000 and an ATS Multi-Piece Pulse Manifold. The Aurora 2000 has a huge compressor housing providing massive air volume, and there's no wastegate, so all the available hot exhaust gases coming out of the engine are spinning the turbine. EGTs are lowered, and boost pressures typically run between 32 and 38 psi, with quick off-the-line and midrange response. Great fun for a daily driver.

The hot exhaust exiting the combustion chambers must flow unrestricted through the exhaust manifold to spin the turbocharger's turbine. ATS has engineered a pulse exhaust-flow design, helping spool up the turbocharger fast with less exhaust backpressure and increase fuel efficiency. And the manifold was pre-tapped for our pyrometer probe. Back on the dyno, the Ram was starting to show impressive results. Horsepower climbed to 275.8, and torque rose to 526. The ATS Aurora 2000 runs about $1664.25, and the ATS Multi-Piece Pulse Manifold will set you back $493.50.