Commenting on the killer Dual-V intercooler hidden under the RK Sport bumper cover, Hahn concedes, "The intercooler is so huge simply because of the 'wretched overkill' personality we wanted this system to exude. Even though we are currently making only about 550 flywheel hp on the stock LS1, this wicked dual-core intercooler will support 1,000-plus hp, and it will not become parasitic in terms of pressure drop, even at those levels. So, while this GTO is putting out 'only' 476 rwhp, the turbosystem's capabilities can be radically upgraded with improvements in the engine's bottom end. Combined with the larger turbos and bigger injectors, this system can be a 1,000-hp-plus package."
The intercooler and induction duct combination is an outstanding accomplishment by itself, combining two gigantic 6-inch tall, 24-inch wide, and 4.5-inch deep bar-and-plate cores into a V-shaped sheetmetal and TIG-welded work of art. Its unique configuration takes the boosted air from each turbocharger and merges it together in the center of the car, where it is then ducted past the MAF meter on its way to the throttle body. Its configuration also greatly reduces the amount of charge air piping normally required to support a twin-turbo design. Bill estimates that well over 100 hours of design and fab time went into this wild prototype intercooler/ducting, and it shows!
Enthusiasts speak of turbocharging and "turbo lag" from the context of 1960s and '70s cars, when engine management and turbocharger design was relatively primitive. Modern turbochargers and improved engine management, coupled with modern engines themselves, produce the ability to build turbo systems with virtually immediate throttle response. The turbochargers on the GTO begin making boost at 2,000 rpm, not very far off idle. With that kind of throttle response, "turbo lag" is a non-issue, even a misnomer.
A well-executed turbo system, with the turbos close to the engine where they can react to exhaust gas temperature rises immediately, is the formula for what Hahn calls "Power on Demand." Bill says, "The power level achieved then becomes simply dependent on how hard one pushes the accelerator, like an infinitely variable supercharger you control with your right foot. No need to wait for higher rpm to get more power, just push the pedal harder!"
In a street turbocharging application, the tightrope walk is a balance between power and excellent response. For a car to be completely tractable, while possessing good throttle response, it all comes down to engine management. Engine management today is a more complex picture, not simply spark and fuel. Current engineering in engine management now involves variable camshaft timing, torque management working with electronic throttle controls, catalytic converter heat management, and a myriad other factors that increase performance, while at the same time improving emissions and gas mileage. Fortunately, the same tools used by OEM engineers to optimize performance, emissions control, and fuel mileage can also be used to optimize a turbocharger system.
At Hahn Racecraft, optimum engine management is the highest priority. Hahn explains, "With the turbos installed, we then need to do the calibration of the computer. Even though this turbo system was designed, fabricated, and installed in a marathon session of only six days prior to the 2004 SEMA show, the actual calibration and validation of the engine management system took a period of months, and is always subject to further improvement should we discover an area that can benefit. The engine management is progressively calibrated with data collected, and then the system is validated in testing and real world driving."