Truckin' May 2005
photography Tim Gavern
Instant Muscle-Truck In A Box
The latest generation of General Motors Duramax turbodiesels, designated LLY, are taking the truck world by storm. Even in stock form, they do everything right: They’re quiet and powerful, they have plenty of torque, and they’re fast.
The LLY Duramax diesel is so hot dealers can’t keep them in stock. This is amazing considering Duramax LLY turbodiesels cost nearly $6,000 more than their gasoline-powered siblings when equipped with the sweet-shifting Allison five-speed automatic transmission. But, even with the additional cost over the gas models, you get what you pay for–the Duramax LLY engine should last a few hundred thousand miles when properly maintained. Plus, the resale value will always be higher.
We’ve found what might be the best way to turn a Duramax LLY into a 9,000-pound musclecar. OK, muscle-truck. Most of you have already heard of Gale Banks, but did you know that his company, Gale Banks Engineering, has been building high-performance diesel products for more than 25 years? Its Big Hoss Bundle is a well-engineered and tested system that is able to generate 124 additional horsepower and more than 305 lb-ft more torque from a Duramax LLY-equipped truck. The difference in the truck is stunning, and the power is both useable and continuous.
The first thing turbodiesel consumers need to learn is that the big black trails of sooty smoke seen in every diesel tuner ad isn’t cool. In fact, it’s a joke. Black smoke is the telltale sign of a diesel engine being over-fueled. Adding fuel without adding proper amounts of air to go with it immediately raises exhaust gas temperature (EGT), which eventually leads to problems and shortens engine life. Gasoline engines throttle by air intake. Diesel engines, on the other hand, throttle by fuel intake. To put it simply, the more fuel a diesel engine takes in, the more power it makes. You can literally push enough fuel into a diesel engine that its physical strength cannot handle it, or there simply isn’t enough air to combust the fuel.
Because diesels make more power by pushing more fuel, many diesel tuners simply add a power programmer, diesel computer tuner, or whatever you want to call it, and call it a day. This is great if you only need extra power for 15 to 20 seconds at a time. Because soon after that, the EGT will skyrocket to the point where the safety temperature-limiting feature of the diesel tuner will shut off the additional fuel. No added fuel means no added power.
Think of it this way: A diesel tuner working alone is like a nitrous oxide system–you can only use it for short power spurts. In the diesel’s case, the extra power stays turned off until the EGT cools down to acceptable levels. Only then will the horsepower be available again. And soon enough, it will be gone until the exhaust cools down again. And so goes the vicious cycle.
Let’s get back to the engine problems that can be traced to continually high EGT from over-fueling. The first is the uncombusted fuel, which you might recognize as the black soot that spews out of the tailpipe and contaminates the engine’s oil. This contamination rapidly breaks down oil, causing premature engine wear. The second is tales on the messageboards of pistons getting so hot they stick in the cylinder bores. That should be proof enough that it isn’t the right way to make power.
Banks’ Big Hoss Bundles are its top-of-the-line systems and include every power-making component in Banks’ power arsenal. First, a Banks Ram-Air lifetime high-flow air filter element supplies cooler, denser air to the engine. Next, a 4-inch stainless steel straight-through Monster Muffler and 4-inch stainless steel Monster Exhaust system with a 5-inch stainless steel double-walled tip cuts backpressure by an amazing 98.37 percent, according to the company. This allows the turbo to spool faster and run cooler. Less backpressure also reduces pumping losses, which is the amount of engine power required to pull air in and push exhaust out.
The turbocharger compresses the intake air, which also, unfortunately, heats it. Banks’ larger intercooler, called a Techni-Cooler, and its larger-diameter boost tubes cool the compressed air and increase its density as much as 10 percent in the Duramax LLY application. Banks is big on air density, and for good reason. To put it simply, for every percentage that the intake air can be made denser, an equal amount of horsepower can be made. In other words, 10 percent more density translates into 10 percent more horsepower. Cooler, denser, more-oxygenated air will allow more fuel to combust completely for more power without increasing EGT. In other words, the power you paid for is there–all of the time, not just when the EGT goes back down. Banks’ Six-Gun Diesel Computer tuner with Speed-Loader option is included to supply the necessary additional fuel for more power. Six-Guns have a six-position dash-mounted knob that increases power in 20 percent increments. Just turn up the knob for more power and suddenly you have a 9,000-pound race truck.