We hear the phrase "bigger is better" all the time, and in many cases, it's true. In the case of diesel performance, by increasing the exhaust diameter, we have seen substantial increases in both torque and horsepower. A minimum of a 4-inch-diameter exhaust is the optimum size to produce maximum exhaust-flow rate and performance.
| 2006 Chevy Silverado 2500HD Buildup magnaflow Performance Exhaust
Noticeable horsepower gains can be accomplished with the installation of a straight-through exhaust system, developing increased torque and power numbers. It's all about air + fuel + flow = power. The diesel exhaust is a major factor in the power-gain equation. The larger-diameter diesel exhaust also assists in relieving the turbine inlet and outlet pressures. The 4-inch-diameter exhaust creates a greater surface area that will dissipate heat better.
If more air is going out, to maximize horsepower, more air needs to be going in. When we upgraded our exhaust system, we also added a new K&N 63 Series AirCharger performance air intake to the equation.
We followed along as Jim Gose and Greg Klimuck installed a MagnaFlow downpipe exhaust and a K&N AirCharger air-intake system that will achieve optimum intake and exhaust flow from the Chevrolet 6.6L Duramax diesel. Richard Waitas then performed some power pulls on the MagnaFlow Mustang dyno.
Performance Exhaust: MagnaFlow Exhaust To achieve a more efficient exhaust system, we cruised over to MagnaFlow Performance Exhaust in Rancho Santa Margarita, California, to document the installation of a MagnaFlow exhaust system on an '06 Chevy Silverado 2500HD, 4x4, 6.6L Duramax diesel. The MagnaFlow exhaust features 4-inch-diameter, mandrel-bent, stainless steel tubing with a spun catalytic converter system. After that, the baseline horsepower and torque were determined: 268.7 max horsepower and 559.8 lb-ft of max torque. After the MagnaFlow downpipe system was installed, the Silverado was strapped down to the Mustang dyno. Dyno results showed noticeable increases: max horsepower was 292 at 2,750 rpm, and max torque was 587.2 at 2,500 rpm.
| The MagnaFlow exhaust is a complete replacement for the factory '06 Chevrolet 2500HD.
Performance Intake: K&N Air Intake
Another factor of the torque/power-gain equation is the air-intake system. To achieve a better air-intake flow rate, we also installed a K&N 63 Series AirCharger air intake system. The K&N AirCharger kit will eliminate airflow restriction, creating more airflow velocity. With K&N's AirCharger heat-shield doghouse design, it will deliver cooler airflow into the intake system, developing more torque and horsepower. We noticed a 15.4hp gain and a 36.8-lb-ft torque increase after installing the K&N AirCharger.
