Welcome back to our series on Big Blue, a modified, Duramax 6600-powered, GMC 2500HD. In Part One, we installed an Auto Meter Dual-A-Pillar pyrometer and boost gauge kit to measure a key, turbocharged diesel tuning factor: turbine inlet temperature. We put the pyrometer's sensor in an exhaust manifold because it was too difficult to tear apart the exhaust to weld a sensor bung at the turbo inlet. Later, we decided the pyrometer would be more accurate with the sensor closer to the turbo. It was no easy job, but removal of the left inner fender and a power steering pipe frame bracket, temporary bending of steering and brake pipes, and plenty of patience had us removing the pipe between the left manifold and the turbo inlet
We reinstalled the bung-equipped pipe with new gaskets, moved the sensor, plugged the hole in the manifold, and rerouted the wiring. Pyrometer readings from the turbine inlet were, now, about 100 degrees Fahrenheit less, and our tuning was much more precise
More Power
Next, was an ECM programming update from Ron Zimmer over at Z-Industries, the engine controls specialist discussed in Part Two. Ron's first effort knocked a whopping 1.1 seconds off Big Blue's quarter-mile time. For this issue of Diesel Power, we, again, installed our Vericom VC2000 Performance Computer in the truck and went testing. The latest Z-I calibration shaved another four tenths off the e.t., and driveablity improved as well. Our performance averaged 15.40 seconds and 93.9 mph, compared to our baseline from Part One of 16.93/82.0. We think Z-Industries does some of the best Dmax reprogramming work in the industry
Still More Power
To date, performance enhancements have been: a Flowmaster American Thunder exhaust system, a Green Filter in the stock air filter assembly, Ron Zimmer's calibration work, and Red Line Synthetic lubricants.
The American Thunder exhaust we installed in Part One comes with a racing downpipe to replace the catalytic converter. Cat removal is illegal for the street but is of interest, considering the number of Diesel Power readers who drag race. With the Flowmaster downpipe in place, a catless Big Blue was another 0.18 seconds quicker and 1.5 mph faster (15.22/95.4) on the drag strip. In addition, we noticed better response as the turbo was spooling up more quickly. The truck was also more consistent leaving the starting line. We suspect cat removal allows the turbo to build boost in a more controllable manner.
What about the aftermarket intake systems, such as airboxes, which are popular with truck enthusiasts? We tested two airboxes for the Duramax on Big Blue. In repeated drag strip tests with street miles in between, both were responsible for slight decreases in performance. We reinstalled the stock airbox with the Green Filter and stuck with that. The O.E. air filter assembly and intake duct is a good design for a Dmax modified to the level of that in Big Blue.
Faster (and Safer) on the DirtBig Blue racks up 4,100 miles a month in California and Nevada, going to construction projects. Some are accessible only on dirt or gravel roads. Time is money, so our hot rod Duramax gets driven pretty fast off road. A bad part of that is flying dirt, gravel, and stone chips sandblasting the headlights. To improve lighting performance and safety, we replaced the lights then added a set of WeatherTech LampGuards, 40-mil, clear, adhesive-backed, polyurethane overlays. LampGuards reduce abrasion and pitting.