Which Parts Should You Add To Your '99 To '02 Cummins First?

The most common parts readers bolt onto their trucks are aftermarket intakes and high-flow exhaust systems designed to increase airflow. Typically, enthusiasts combine those parts with a module or programmer that adds more fuel. Combined, that's about $2,000 worth of components to add to your truck. But what if you don't have $2,000 to spend at one time? Which part should you add first? That's exactly what we set out to uncover in our latest test.

Our guinea pig was an '02 two-wheel-drive Dodge Ram 3500 dualie with a VP44-injected Cummins 24-valve engine, and an NV5600 six-speed manual transmission. The truck was bone-stock-right down to the tires-and had 85,000 miles on the ticker. The results of our testing are intended to provide information about a logical upgrade path for any comparable truck. However, it should be noted that every diesel vehicle will respond differently to modifications.

Scientific Method
The scientific method requires experimentation, and diesel performance is a science these days. The key to accurate testing is limiting the number of variables to isolate each component that you wish to test. Ideally, we'd evaluate each part under exactly the same conditions for hundreds or thousands of miles to minimize anomalies. Still, every effort was made to limit the variables that might affect mileage and power. All dyno pulls were made with the hood open and a fan pushing air through the engine bay to minimize heat soak. The mileage testing was performed on the same 80-mile loop of rural road with the cruise control set at 65 mph for as much of the drive as possible. In addition, the same fuel station, and even the same pump, was used to fuel the truck between mileage runs.

The Criteria
We use this Dodge to regularly tow a fifth-wheel trailer or a car trailer with a Jeep on it. The criteria for parts chosen was that components had to be reasonably priced and had to add more usable horsepower, torque, and mileage without sacrificing reliability. Additionally, the parts had to bolt on with basic handtools over the course of a day. Each part was individually dyno-tested at Imler Diesel Performance on its Mustang dyno in order to determine the added torque and horsepower each item contributed. Then the parts were combined and retested to determine the collective improvements.

Intake System
Factory engineers balance costs and noise reduction with airflow, which results in compromises that leave power on the table. S&B Filters offers an intake for the 24-valve Dodge (P/N 75-5044) that flows 55 percent more than the factory intake, thanks to its cotton gauze filter with deep pleats and a larger overall size with increased surface area. The improved airflow does not come at the expense of filtering, as S&B performs the ISO 5011 Air Filtration Test Standard on all its filters. An S&B intake manifold was added in conjunction with the intake kit. The S&B intake manifold is CNC-machined from cast aluminum and is said to be 45 percent less restrictive than the stock intake manifold. The S&B piece features an O-ring to ensure leak-free performance and is tapped with five 1/8-inch NPT ports for everything from pressure sensors to nitrous nozzles to water-methanol injection.

If you're paying close attention, you will note that we just got done stating that we wanted to limit variables, then we added the S&B intake manifold at the same time as its air intake kit. S&B products are very cost competitive, and we were able to add both the intake and the manifold for less than $500, which is less than the price of just an air intake from many manufacturers. The intake system did not seem to be the most restrictive stock component, but it did provide more than a 1/2-mile increase in fuel mileage on our test loop and lowered EGT. The S&B intake also produced an audible whistle inside the cab, which we consider music, but some might find intrusive.