Jeep Grand Cherokee SRT-8 [UK] (2007)

The SRT powertrain engineers who developed the Jeep Grand Cherokee SRT-8's engine achieved more horsepower by increasing the capacity, raising the compression ratio, redesigning the cylinder head air intake and exhaust systems for increased flow, and enhancing the internal components to allow higher engine speeds (rpm). Strengthened components include a reinforced engine block, forged steel crankshaft and high-strength connecting rods.

The cylinder bore of the 90-degree V8 was increased by 3.5 mm, boosting displacement from 5.7-litres (5654 cc) to 6.1-litres (6063 cc). The compression ratio was raised from 9.5:1 to 10.3:1, unleashing more energy in the combustion process. Maximum power of 420 bhp is generated at 6,000 rpm, while maximum torque (420 lb.-ft.) is produced at 4,800 rpm.

Engine breathing was increased with new high-flow cylinder heads featuring 16 larger diameter valves (2 per cylinder) and reshaped cylinder ports to maximize airflow. A special intake manifold was designed with larger diameter runners for higher-speed tuning and the exhaust 'header' pipes have individual tubes encased in a stainless steel shell, routed through a larger-diameter (70 mm vs. 63.5 mm) exhaust system with 101 mm chrome tail pipes - all unique to the Jeep Grand Cherokee SRT-8's 6.1-litre HEMI engine.

Performance-oriented camshaft profiles were developed to balance total vehicle requirements, simultaneously allowing more air in and out of the cylinders and enabling the engine to attain higher revs. SRT engineers increased the HEMI's peak engine speed nearly 20 percent, to 6,000 rpm (up from 5,000 rpm).

The high-performance 6.1-litre HEMI is further strengthened with a host of redesigned components, including a reinforced engine block with increased coolant flow, forged steel crankshaft, high-strength powdered-metal connecting rods, floating-pin pistons (cooled by oil squirters), an oil sump modified for reduced oil foaming and hollow, sodium-filled intake and exhaust valve stems to help dissipate heat more efficiently.

The 6.1-litre HEMI's power is channelled through an A580 five-speed automatic transmission with specially calibrated AutoStick® driver-selectable range control, which offers fully automatic operation or sequential manual gear selection. A heavy-duty four-flange prop shaft sends the torque from the transmission to an upgraded differential and rear axle.

SRT-8 Ride and Handling

The Jeep Grand Cherokee SRT-8 chassis has been fine-tuned to deliver outstanding SRT-style ride and handling across the broad dynamic range that enthusiastic Jeep owners are sure to exploit to the fullest extent. While the existing Grand Cherokee's suspension layout - independent with double wishbones at the front and a live axle located with multiple links at the rear - is retained, numerous enhancements have been made.

The SRT-8's unique chassis set-up includes tuned Bilstein dampers, specially tailored spring rates and suspension bushings and larger-diameter anti-roll bars. The ride height is lowered by 25 mm, reducing aerodynamic drag, lowering the centre of gravity and enhancing stability and creating an aggressive stance. The Electronic Stability Program (ESP) is specially re-tuned to match the car's performance characteristics. The power-assisted rack and pinion steering is higher geared for a more agile response, with 2.85 turns lock-to-lock for an 11.3 metre turning circle, compared with 3.14 turns on the regular Grand Cherokee.

Contributing to its aggressive appearance, while providing both a cosmetic hype and genuine performance boost, the Jeep Grand Cherokee SRT-8 is equipped with larger diameter, unique five-spoke 20-inch forged aluminium wheels shod with high-performance 245/45 ZR20 all-season tyres, with a run-flat capability.

SRT-8 Upgraded Braking

The braking system of the all-new Jeep Grand Cherokee SRT-8 was upgraded to provide benchmark braking performance, setting a new standard for SUVs and a potent counterpoint to the vehicle's amazing acceleration and performance.

To stop the vehicle safely and predictably from high speeds, all four discs are fitted with ultra-high performance Brembo racing-style callipers, equipped with four pistons for even greater clamping performance. Up front, there are 360 x 32mm ventilated discs, with 350 x 28mm ventilated discs at the rear. Stopping from 62 mph is accomplished in just 125 feet (38.1 metres).

Functional SRT Exterior Enhancements

Appropriate to its role as 'the quickest-ever Jeep' the Grand Cherokee SRT-8's exterior styling follows the SRT credo with functional exterior enhancements unique to this model, which boost performance and resonate with brand character. The new model's lowered, aggressive stance shows its unmistakable Jeep identity endowed with Street and Racing Technology DNA.

An all-new front fascia embodies aerodynamic improvements that reduce lift and drag, while providing sufficient airflow to meet the increased cooling demands of the larger HEMI engine. Unique air intake ducts also help to cool the front brakes. A new rear fascia incorporates an aggressive centre cut-out to accommodate the dual 101 mm diameter exhaust tail pipes. In addition, specially designed side sill extensions help to increase downforce.

SRT-8 Unique Interior Features

The cabin of the new Jeep Grand Cherokee SRT-8 is distinguished by power-adjustable, deeply sculpted performance front seats complete with uniquely patterned suede inserts designed to hold the occupants securely during spirited driving. The heated front seats are also equipped with memory functions and the height-adjustable steering wheel ensures that every driver can find the 'perfect' seating position from which to fully exploit the SRT-8's performance. All Jeep Grand Cherokee SRT-8 vehicles feature an interior trimmed in Medium Slate Grey leather.

Other SRT-only trim includes a special 'carbon-fibre technical' leather trim for a more positive grip, which is applied to the steering wheel and gear selector. The centre stack features a unique finish in 'refined aluminium' which is also applied to shifter console and door-switch bezels. The steering wheel frames comprehensive instrumentation, including a 180 mph (290 km/h) speedometer, tachometer and engine temperature gauges, all trimmed with a blue accent and located in a carbon-fibre trimmed binnacle.

Premium amenities within the Jeep Grand Cherokee SRT-8 cabin include a standard AM/FM stereo radio with six-disc CD changer, 280 Watts audio system powering a six-speaker Boston Acoustics speaker system, with steering wheel-mounted controls.