Jeep GC SRT-8: Part I
2006 Grand Cherokee SRT8: The Quickest, Most Powerful Jeep Vehicle Ever
NEW YORK, March 23 /PRNewswire-FirstCall/ -- Jeep(R) vehicles are known worldwide for their capability, utility and distinctive style.
The all-new 2006 Jeep Grand Cherokee SRT8 combines those qualities with Street and Racing Technology's (SRT) balanced approach to performance, resulting in the quickest, most powerful Jeep vehicle ever created, and the ultimate performance sports utility vehicle.
"Jeep vehicles lead the way in performance and versatility," said Jeff Bell, Vice President, Jeep, Chrysler Group. "The all-new 2006 Jeep Grand Cherokee SRT8 adds a new dimension to performance and versatility -- and value. With its SRT-engineered 6.1-liter HEMI(R) engine and specially developed full-time four-wheel drive system, the 2006 Jeep Grand Cherokee SRT8 provides stunning performance in an amazing variety of driving conditions.
"The all-new 2006 Jeep Grand Cherokee SRT8 marries Jeep capability with SRT performance to create a vehicle that will leave in its dust competitors that cost twice the price," Bell added.
Powered by a 6.1-liter HEMI producing 415 horsepower (85 more horses and 25 percent more power than the 5.7-liter HEMI-equipped 2006 Jeep Grand Cherokee) and 410 lb.-ft. of torque, the all-new 2006 Jeep Grand Cherokee SRT8's performance numbers include 0-60 mph in under 5 seconds, 0-100-0 mph in the low 19-second range, and 60-0 mph braking distance of approximately 125 feet.
"When we set out to create the first Jeep-branded SRT vehicle, the 2006 Jeep Grand Cherokee presented us with an incredibly capable starting point," said Dan Knott, Director - Street and Racing Technology, Chrysler Group. "With an infusion of SRT DNA, the 2006 Jeep Grand Cherokee SRT8 is the new benchmark performance SUV. It has the raw power to outperform the Porsche Cayenne Turbo, while providing exceptional ride and handling, world-class braking, race-inspired interior appointments and functional, performance- oriented exterior enhancements."
Four-Wheel Drive System
To create the first SRT vehicle with full-time four-wheel drive, SRT engineers developed a drive system that was lightweight, yet robust and reliable enough to handle massive amounts of horsepower and torque from the 2006 Jeep Grand Cherokee SRT8's powertrain. One part of the equation was to create a new transfer case, combining housing components from two existing units with the upgrades needed to make it SRT-capable.
SRT engineers opted to use the front half of a Jeep transfer case chosen for its capability and light weight. It was mated to the rear half of a heavier-duty case, chosen for its ruggedness and ability to house the electronic full-time four-wheel drive system components. The transfer case output shaft was upgraded to handle high torque generated by the SRT 6.1-liter HEMI.
The result is the all-new 2006 Jeep Grand Cherokee SRT8's unique transfer case, which provides the necessary power-handling capabilities for the Grand Cherokee SRT8 while weighing 60 pounds less than a Jeep heavy-duty case.
Under normal driving conditions, from 5 percent to 10 percent of torque is directed to the front wheels, but as much of the 6.1-liter HEMI's torque as needed can be directed forward when additional traction or stability is required. Remaining torque is sent via a heavy-duty driveshaft designed for the European Jeep Grand Cherokee diesel model, to a Dana 44 rear differential upgraded with a larger ring gear within a new axle housing.
"We wanted the acceleration that only four-wheel-drive can provide," said Knott. "Our goal for the 2006 Jeep Grand Cherokee SRT8 was to have a well- balanced vehicle with a high fun-to-drive quotient. The SRT-developed electronic four-wheel drive system is perfectly suited to this."
Powertrain
Providing horsepower and torque to the unique SRT four-wheel drive system is a specially tuned version of the new 6.1-liter SRT HEMI engine. Inspired by the original family of HEMIs, the SRT 6.1-liter HEMI employs the namesake hemispherical combustion chambers that provide power and efficiency, while retaining classic HEMI visual cues including the orange-painted cylinder block and black valve covers.
With the Chrysler Group's clean and efficient 5.7-liter HEMI as a starting point, SRT powertrain engineers developed 85 more horsepower over the Jeep Grand Cherokee's 5.7-liter HEMI by adding more cubic inches, increasing the compression ratio, redesigning the cylinder head, intake and exhaust systems for increased flow, and increasing engine speed.
For more displacement, SRT engineers bored out the diameter of the cylinders in the HEMI by 3.5 millimeters each in order to increase the total displacement to 6.1 liters from 5.7 liters.
Compression ratio was also increased to 10.3:1 from 9.6:1, increasing engine efficiency and power.
Engine breathing was increased with new higher-flow cylinder heads, a specially designed intake manifold and fresh-air induction system (which allows water-fording capability of up to 19 inches), and exhaust headers with individual tubes encased in a stainless steel shell. All are unique to the 6.1-liter HEMI engine. Larger-diameter valves and reshaped ports in the heads allow for maximized air flow. The intake manifold was designed with larger- diameter and shorter runners for higher-speed tuning. Exhaust is routed through a large-diameter (2.75-inch vs. 2.5-inch) exhaust system with 4-inch chrome tips.
To further increase horsepower, performance-oriented camshaft profiles were developed to allow more air in and out of the cylinders, as well as manage a higher engine speed. SRT engineers increased the HEMI's peak power output engine speed nearly 20 percent to 6,000 revolutions per minute (rpm) from 5,000 rpm. Intake and exhaust valve stems are hollow, and the exhaust valve stems are filled with sodium to help dissipate heat more efficiently.
The high-performance SRT 6.1-liter HEMI is strengthened with redesigned components, including a reinforced engine block, forged steel crankshaft, high-strength powdered-metal connecting rods, floating-pin pistons (cooled by oil squirters), and an oil pan modified to manage oil return to the pan sump at high engine speeds.
Power from the SRT 6.1-liter HEMI is sent through a special torque converter to an SRT-upgraded A580 five-speed automatic transmission. Torque is then sent to front and rear differentials through a specially designed transfer case.
