2005 GMC Sierra Duramax - The Next Level

Perhaps the most common question we get in the diesel industry is, "What can I do next?" Most people are daring enough to buy a programmer and maybe make a few other modifications, but then they stop and leave the full race stuff like cams and ported heads to the really hard-core drag racers and sled pullers. We knew there had to be a middle ground, so we set off to find out just how fast you can go with bolt-on parts.

While we were out looking for a truck that would satisfy our needs, one found us. At the '07 DHRA Vegas Nationals, the winner of the 12.0 class was Joe Komaromi from Pacific Performance Engineering (PPE), and he did it with all bolt-on parts. It seemed like exactly what we were looking for, so we got Komaromi to give us the inside scoop on what makes the white monster tick.

Step One: The BasicsMany of you may have already completed step one, which includes gauges, an exhaust, and a programmer. A lift pump can also keep the injection pump supplied with plenty of fuel, so that's not a bad idea. But be warned-even a programmer can roast a stock Allison transmission on the highest settings. The PPE Hot + 2 Xcelerator has settings for an extra 40 hp (at the crank) all the way up to 350 hp, so if you run the higher settings, your transmission may be on its way out. Komaromi recommends no more than PPE's 160hp Stage 3 tune-about 100 rear-wheel horsepower (rwhp)-with a stock transmission. It's a bummer to pay a lot of dough up front, but a performance transmission is the next step you have to take before you can add more horsepower.

Step Two: TransmissionKeeping in mind our lofty goal of 650 rwhp, a simple torque-converter swap isn't going to cut it. For his truck, Komaromi uses a Stage V transmission kit, which includes a new converter, a valvebody kit, a power valve, and upgraded clutches. The kit retails for approximately $4,100, plus the labor to install the parts, but at such a high power level, there is no way around the expense. What you'll get for your money, though, is a transmission that will live through almost any upgrade you can throw at it. Better to do it once and get it over with than to have to take the Allison apart every time you want to add more power.

Step Three: Turbocharger UpgradeWith a programmer cranked up to its highest level and a transmission that can handle the power, your truck should now be at the 450-rwhp level. The stock Duramax turbo can only spin enough air to support about 500 rwhp, so a turbo upgrade is next on the to-do list. On his truck, Komaromi uses a Garrett GT4094R turbo, which flows enough air for almost 700 hp at the wheels.

Step Four: Dual FuelerAir and fuel are still related, even in a diesel, so with more air from an upgraded turbo, more fuel can be added. For this, Komaromi uses a dual-fueler kit, which adds a second CP3 injection pump on the top driver side of the engine. The second CP3 helps the engine keep its rail pressure up and ensures the engine will get all the fuel it needs with the addition of the turbocharger. Komaromi also uses his Duramaximizer on this step, which increases rail pressure so the thirsty CP3s, turbo, and programmer can work as one big, happy family.

The Results: 641 Rwhp!The results of combining all the proper parts speak for themselves. While the truck didn't make 650 rwhp as we had hoped, we'll let Komaromi off the hook because it made 641 hp and 1,146 lb-ft of torque on the chassis dyno, and 99 percent of our goal is good enough for us. Not only that, but on regular street tires, the truck ran an astounding 11.83 at 115 mph in the quarter-mile at a race weight of about 6,700 pounds. The estimated cost of all the parts you would need to replicate this truck is about $13,000, which may seem like a lot until you realize that amount of money will get you a truck that reliably makes more than 800 hp at the flywheel, gets good fuel mileage, tows whatever you want, and is off-road capable. What vehicle other than a hopped-up diesel truck can do that?