| The test vehicle used in this article was an '07 Chevy Silverado 2500 Classic with an LBZ Duramax engine. Before we got ahold of it, the truck was completely stock with no upgrades of any kind.
The 6.6L Duramax diesel is an extremely versatile engine with lots of torque and plenty of durability-as the name would imply. For anyone looking for an excellent tow rig, race truck, or daily driver, this is one of the best to ever roll off an American assembly line. As is the case with most late-model offerings, improving the breed is a matter of careful engineering and creative thought. Yet when it comes time to modify your diesel engine, which modification should you do first?
With today's computer-controlled engines, the key to increasing performance is usually working with the high-tech systems rather than trying to work against them. That was the key motivation behind the changes made to this '07 Silverado 2500 test vehicle.
The '07 LBZ Duramax used for this test belonged to Paul Gonzalez. His truck was to receive two modifications that every diesel enthusiast makes: a swap to a 4-inch diameter exhaust system and a plug-in programmer. We felt that both mods were real-world changes that would help with the exhaust flow and maximize the efficiency of the diesel system.
| The Hushpower muffler fit in the factory location and featured a 4-inch inlet and outlet for this application. Larger 5-inch diameter mufflers are also available for custom exhaust applications.
The new Hushpower exhaust system Gonzalez spec'd for his LBZ Duramax diesel came with 4-inch tubing, but Hushpower also offers mufflers in 3- and 5-inch diameters. The system featured aluminized metal tubing, the proper sized Hushpower muffler, and all of the hangers and hardware required for easy installation. No welding was required and the factory hangers were used.
The TestWe began by dyno testing the rear wheel horsepower of the stock truck in order to achieve a baseline figure. The test netted a decent number of 315 hp and 588 lb-ft of torque. From there, we headed to Paul Gonzalez Custom Cars for the exhaust system swap. The Hushpower 4-inch kit matched the stock 4-inch system originally installed on the truck. The OEM resonator delivered from the factory was not used in this system, and the factory kinks in the tubing were eliminated with the Hushpower exhaust kit installed.
| Note the cones visible inside the muffler, which are said to be tuned to create excellent flow and a performance sound. They will not burn out like glass packs or mufflers of lesser quality.
Installing the ExhaustUsing a vehicle lift, the Hushpower exhaust system install took about an hour, including the time required to take pictures for this article. The hardest part was removing the downpipe that attached to the turbocharger. The key was not to damage the coupler, and make sure the new downpipe was attached correctly. All of the original rubber hangers were reused in this install, and because of the low mileage on the truck, none required replacement. If your truck is older and the hangers are not in perfect shape, they should be replaced.
Programming PowerFor our test, we also used a new Superchips Cortex programmer. This is Superchips' newest programmer for the LBZ Duramax. The programmer comes with a two-year drivetrain warranty and features three levels of performance upgrades. By simply plugging the programmer into the data link connector under the steering wheel, we could select either a Tow performance setting or two additional higher power levels. The programmer also retains the original computer program features so that the stock settings can be reinstalled. All three of the performance levels were tested at the Westech Performance dyno facility.
| The Hushpower exhaust kit included all of the tubing, hanger hardware, and complete instructions.
The ResultsOur dyno testing proved a number of things right off the bat. The test with the Hushpower system alone netted a 13-lb-ft increase in torque and 7 more horsepower. The important part of this change is that the free-flowing system raised the performance potential for the programmer upgrades that would come next.
When the Superchips Tow performance setting was uploaded, power jumped from 601 lb-ft with the new exhaust to 656 lb-ft. With the Level 1 performance program uploaded, that number jumped to 723 lb-ft of torque. Finally, the Level 2 performance program was selected, and it generated an amazing 743 lb-ft of torque at the rear wheels, a full 142 more lb-ft than the stock truck made with the Hushpower exhaust.
