Jefferson Avenue North, Detroit, USA, and Magna Steyr Assembly Plant in Graz, Austria
EPA Vehicle Class
2006 model: November 2005
2007 model: July 2006
2006 model: January 2006
2007 model: September 2006
The 6.1L-liter V8 HEMI made its Jeep debut in the 2006 Grand Cherokee SRT8 which went on sale in January of 2006. When SRT powertrain engineers set out to develop a more powerful HEMI they were mindful of the engine’s heritage, which led to adopting traditional HEMI engine cues including an orange-painted cylinder block and black valve covers. SRT engineers who developed the 6.1L engine achieved more horsepower by adding more cubic inches, increasing the compression ratio, and redesigning the cylinder head, intake and exhaust systems for better flow and increased 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. Cylinders are honed with torque plates to ensure a truer bore, to reduce friction and increase power.
Engine breathing was increased with new higher-flow cylinder heads, a specially designed intake manifold, and exhaust headers with individual tubes encased in a stainless steel shell, all 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 runners allow increased gas flow while maintaining fast catalyst light-off, while adding 12 horsepower over the 5.7-liter engine’s cast manifolds. Exhaust is routed through a large diameter (2.75-inch vs. 2.5-inch) exhaust system with 3.5-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. A billet steel, high-strength camshaft features more overlap and lift for better performance. Silent chain, 5-bearings. Bi-metal material except number 3 Babbit. Deep-fillet rolled journals for improved fatigue life, press fit damper to minimize torsional vibration.
SRT engineers increased the HEMI’s peak power output engine speed by 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 micro-alloy steel crankshaft with retuned damper, high-strength powdered metal connecting rods and floating-pin pistons. The pistons are cooled by oil squirters, aimed at the underside of each piston to aid piston cooling for engine durability. A special oil pump pressure relief valve is added to accommodate the squirter oil flow. The oil pan and windage tray are modified to manage oil return to the pan sump at high engine speeds and improve power.
6.1-Liter, HEMI® V-8, 90-degree V-type, liquid-cooled. The development of the SRT 6.1-liter HEMI V-8 started with a world-class foundation – the Chrysler Group’s 5.7-liter HEMI V-8 engine. From there, a team of SRT powertrain engineers integrated race-proven engine technologies to create the powerful new SRT 6.1-liter HEMI.
Bore x Stroke
4.055 x 3.58 (103 mm x 90.9 mm). To get more air in and out of the cylinders, SRT engineers bored out the diameter of each cylinder by approximately 3.5 millimeters in order to increase the total displacement from 5.7 liters to 6.1 liters. Cylinders are honed with torque plates to ensure a truer bore, to reduce friction and increase power.
A billet steel, high-strength camshaft features more overlap and lift for better performance. Silent chain, 5-bearings. Bi-metal material except number 3 Babbit. Deep-fillet rolled journals for improved fatigue life, press fit damper to minimize torsional vibration
14 qt. (13.25L)
Deep-skirt cast-iron block with cross-bolted main bearing caps, aluminum alloy heads with hemispherical combustion chambers
Nodular cast iron, tuned assembly vibration damper, 6 bi-metal bearings. The crankshaft is forged from micro-alloy steel and rotates in tri-metal main bearings for high-load capability. The crankshaft damper is retuned for higher engine speeds.
Cylinder head ports are designed with larger cross-sectional area. This allows 11 percent higher flow in the intake ports, and 13 percent higher flow in the exhaust ports.
370 cu. in. (6059 cu. cm)
Dual close-coupled three-way catalytic converters, quad heated oxygen sensors and internal engine features
EPA Fuel Economy
12 / 15
1-8-4-3-6-5-7-2 (drivers side, from front of engine 1,8,4,3. Passenger side, from front of engine 6,5,7,2)
Sequential, multi-port, electronic, returnless. Fuel injector flow capacity is increased by 14 percent over the 5.7-liter engine. Electronic throttle control is shared with the 5.7-liter HEMI, but breathes through a revised high-flow air cleaner box outfitted with a tuned resonator delivering a deep performance sound character (and good for an extra eight horsepower).
Premium 91 octane (R+M)/2 recommended
Headers / Exhaust
Individual tubes encased in a stainless steel shell. Exhaust runners allow increased gas flow while maintaining fast catalyst light-off, while adding 12 horsepower over the 5.7-liter engine’s cast manifolds.The 6.1L exhaust system uses two catalytic converters located in the front exhaust pipe, and a single muffler and a duel tailpipe/resonator assembly. The front exhaust pipe/catalytic converter assembly is a hydra-form thin wall air gap design. This design is used to reduce heat, noise and improve emissions.
To control the combustion process, SRT engineers fine-tuned the engine management system using dual wide band knock sensors with premium fuel.
Pressure feed – full flow filtration
Continuing its air-pumping efficiency, engine breathing is improved with specially designed intake and exhaust manifolds. The cast aluminum intake manifold is designed with shorter, larger-diameter and tapered runners for high-speed tuning. Internal runners are core-dipped to smooth the runner finish and improve air flow. The exhaust manifolds are equipped with ball flange outlets to assure a tight seal and strain free connections.
Max. Engine Speed
6400 rpm (electronically limited)
7 qt. (6.6L). The oil pan and windage tray are modified to manage oil return to the pan sump at high engine speeds and improve power.
Aimed at the underside of each piston, added to aid piston cooling for engine durability. A special oil pump pressure relief valve is added to accommodate the squirter oil flow.
Pistons and rods
Larger-diameter, flat-top pistons with high-load capability are specified to handle the SRT 6.1-liter HEMI’s compression ratio, which was increased to 10.3:1 from 9.6:1. Connecting rods are redesigned and make use of higher-strength powder metal material. New floating piston pins are introduced to handle higher loads.
Power (SAE net)
420 bhp @ 6200 rpm
Air-fuel mixtures are ignited by two spark plugs, with platinum tips, in each cylinder. Spark plugs are fired by individual coils for each cylinder, sitting on isolated cylinder head covers, which are adorned with a traditional HEMI black wrinkle finish.
Body Diameter 0.8420 – 0.8427 in. (21.387 – 21.405 mm)
Pushrod-operated overhead valves, 16 valves, eight conventional hydraulic lifters, all with roller followers. Intake valves feature hollow stems and 2 mm larger heads compared to the 5.7L engine, allowing more air flow. The hollow exhaust valve stems are filled with sodium to dissipate heat efficiently. Premium valve springs with external dampers enhance the valvetrain and enable higher engine speed operation to 6,400 rpm. The valvetrain system enhancements allow the peak output engine speed to increase to 6,000 rpm from 5,000 rpm – a 20 percent increase.
Valve head diameter
Intake 2.07 – 2.08 in. (52.67 – 52.93 mm) / Exhaust 1.57 – 1.60 in. (40.37 – 40.63 mm)
Type and Description
W5A580 5-speed automatic. Adaptive electronic control, Performance tuned AutoStick® driver-interactive manual control and electronically modulated torque converter clutch.
Final Drive Ratio
Overall Top Gear
SRT Transfer Case
Type and Description
SRT NV146. Active full-time single-speed with variable torque, solid electronically controlled clutch pack in center differential and open front and rear differentials. The NV146 transfer case provides On-Demand Active Four-Wheel Drive for optimum traction in a wide range of conditions. The transfer case uses the electronically controlled clutch pack to distribute between 0% and 50% of the available torque to the front axle. The NV146 electronics provide an active system because it can anticipate and prevent slip.The NV146 single-speed transfer case provides the following benefits:
No shift lever or driver interaction required.
On-demand four-wheel drive provides smooth operation and vehicle stability under all conditions because torque is constantly being transferred.
Even torque distribution provides traction to maintain forward motion under most conditions.
The Brake Traction Control System (BTCS) works in tandem with on-demand four-wheel drive. BTCS provides resistance to any wheel that is slipping to allow additional torque transfer to wheels with traction.
Robust design and improved sealing enhance reliability.
Controls for the NV146 transfer case active clutch (torque biasing device) are located in the Final Drive Control Module (FDCM) and communicated on the CAN C bus. The FDCM monitors wheel speeds at the front and rear axles to detect wheel slippage. A complete vehicle dynamics model calculates slip at each tire for given vehicle-operating conditions. The clutch pack in the transfer case is engaged to minimize the speed difference between the front and rear axle, resulting in torque transfer to the axle with higher traction. The electronically controlled wet clutch pack uses an electric motor to actuate a sector plate. The sector plate actuates a clutch lever that applies normal force to the multi-disc wet clutch pack bridging the differential. The clutch discs are alternately splined to the front and rear driveshafts. When normal force is applied to this clutch pack, torque is transferred to equalize speed differences between front and rear axles.
Electronic On-Demand 4 x 4
Center Differential Type
Electronically controlled clutch pack torque transfer