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The SleeperMax: 2006 GMC Sierra 2500HD

Episode Two: Testing PPE's Towing Twins On An '06 LBZ Duramax

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For our second installment of the SleeperMax saga, we looked to install a set of twin turbos on Joe Komaromi's '06 LBZ. With a single Garrett GT3788R turbo and a light sprinkling of other modifications, we'd already hit 576 hp on Joe's Mustang II load dyno and run 8.31 seconds at 83.4 mph in the eighth-mile. Although our EGT wasn't sky-high during our dyno runs (1,300 degrees at peak power and 1,500 degrees by the end of the run), we decided to go with a set of Towing Twins to bring EGT completely back to the safe zone. Even though the single turbo cleaned up all the smoke with the PPE Hot+2 E.T. set on Level 5, we figured more boost would still equate to faster track times-especially since both of the turbos would be right in their efficiency range, and boost would be limited to 50 psi as to not overwhelm the stock intercooler.

Towing Twins
Let's be honest. With a suggested retail of about $8,000, PPE's Towing Twins setup is not a budget turbo kit. But it is a very versatile and well-engineered setup, with dual ball-bearing water-cooled turbochargers, heavily reinforced mounting positions, wastegates, and strengthened up-pipes. Spooling is unbelievably quick due to the ball-bearing design. In fact, not only was there no smoke during our dragstrip runs-there was no smoke while spooling, either. The ball-bearing turbos also use less oil than conventional chargers, so no additional strain is placed on the vehicle's oiling system. We can honestly say these Towing Twins are just about everything you would want in a turbo system.

Irwindale Speedway
With Associate Editor Jason Sands behind the wheel, our first run was a weak 8.44 seconds at 85.3 mph. The difference was in the launch, as a 2.0-second 60-foot time was significantly slower than the 1.84 we cut last time. On run number two, the boost was upped to 12 psi on the launch, and the result was a 1.79-second 60-foot time, and an eighth-mile time of 8.02 seconds at 86.6 mph. Even with no smoke, adding the twins and increasing boost from 30 psi to 52 psi had given us a three tenths, 3-mph gain in the eighth-mile, which equates to nearly half a second in the quarter-mile. The truck was definitely making more power, and we couldn't wait to see what it did on the dyno.

On the Rollers
Since the twins went down the track smoke-free, our only dyno test was with the PPE Xcelerator on Level 5-the highest level we could install in the computer without dropping fuel rail pressure. Our previous testing on Level 5 with the single turbo had yielded 576 rear-wheel horsepower and 1,068 lb-ft of torque. EGT was 1,300 degrees at peak power, and 1,500 degrees by the end of the run. We figured the added airflow from the twin turbos would make more power while dropping EGT considerably, and they did just that-although the horsepower gains weren't at all what we expected. After the rollers stopped, the truck had made 587 hp and 1,102 lb-ft of torque-a gain of 11 hp and 34 lb-ft. This was far less than we expected after our dragstrip runs, which indicated a power gain of 50 to 70 hp. The drop in EGT, on the other hand, was astounding, as we couldn't get the truck to break 1,200 degrees if we tried, even on a loaded, 30-second dyno pull.

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