The concept of diesel performance used to be a contradiction. It often involved bolting an expensive aftermarket turbo system onto a heavy truck barely capable of getting out of its own black cloud. GM's 6.2L diesel was notorious for its unspectacular power-to-weight ratio, and the 6.5L version famous for powering the military Humvee was marginally better.

GM finally entered the light-duty diesel market for the 2000 model-year with its 6.6L Duramax, developed with Isuzu. The aftermarket finally had a GM oil-burner worth hot-rodding. Thanks to computer-controlled engine management, huge performance gains of 50 percent or more could be achieved by hijacking the factory software. Aftermarket hard parts such as freer-flowing exhausts still have their place, but electronic programmers and engine modules really pump up the power by changing the fuel-injector pulse to squirt more fuel, then tuning the combustion timing and turbo boost to burn the extra fuel.

That's good and bad. Obviously, a lot more fuel and significantly extra air equals major power improvements. But, there are pitfalls: More power generates more heat, and the factory gear train was engineered to work with stock engine output. So, the diesel aftermarket's primary challenge isn't just making power but instead involves using as many of the vehicle's PCM (powertrain control module) signals to reliably get the power to the ground.

Several diesel power systems are currently on the market. In general, their price reflects the amount of engineering that goes into the product. Some lower-end systems increase fueling to make power but don't address other powertrain parameters. Depending on usage, these lower-priced systems might work well when used in conjunction with aftermarket gauges for a driver who constantly monitors his engine's vitals.

On the other end of the spectrum are fully featured systems that control automatic transmission functions, in addition to adding more fuel, boost, and timing. The Edge Juice With Attitude is an example of one of these higher-end systems currently available for the Duramax. Built-in features, such as gauge-like engine and transmission monitoring on a digital display and automated safeguards that hold back fuel under danger-zone conditions, reflect the level of engineering expertise behind the product.

Under the Hood
Edge's Juice power module plugs into factory sensors in the engine compartment. This allows the Juice to intercept signals between the truck's PCM and the engine, constantly optimizing fueling and timing in real time, based on the selected power level. The Juice offers four levels, maxing out at 90 hp/200 lb-ft, and adding Edge's optional Attitude monitor/controller yields an extra power level in addition to on-the-fly level-changing capability and a host of other features detailed below. For those who don't choose to step up to the Attitude-and who do any diesel performance modification-Edge recommends adding a complete set of aftermarket gauges for powertrain monitoring.

Edge also offers a competition-only Hot Juice With Attitude that adds 150 hp/350 lb-ft of torque. It has an even more aggressive fuel curve than the regular Juice and is engineered for trucks that have extensive aftermarket modifications, including cold-air systems, oversized turbos, free-flowing exhausts, and built transmissions. An '01-'04 LB7 Hot Juice has been available for awhile, and an LLY system is scheduled for release around press time.

Monitoring/Controlling
For less than the cost of aftermarket pyrometer (EGT), boost, and tranny temperature gauges and their respective pods/mounts, Edge offers its optional Attitude monitor/power controller. It uses a backlit LCD screen to display a variety of powertrain-related information. The driver can select any two parameters to show as bar graphs or as many as four powertrain functions to monitor digitally, including Turbo Boost, EGT, actual speed (corrected for non-stock tire diameters), throttle position, engine rpm, torque converter clutch status, engine load, transmission clutch slippage, and current gear backdown due to high EGT.

Edge's Juice With Attitude kit includes the Juice power module, which has built-in wiring leads for the Attitude monitor/controller, an Attitude mounting arm, and an EGT thermocouple (not shown). The new A2 Attitude with a color monitor, a GPS navigation, and a wireless back-up camera should be available by press time.