A popular cost-conscious alternative for Challenger owners to the 5.7L and 6.4L Hemi engines is the 3.6L Pentastar engine. It replaced the 3.5L engine, in 2012, and is rated at an impressive 305 horsepower and 270 lb.-ft. of torque, with 90% of its torque available from 1,800 to 6,350 rpm. Performance from this modern 6-cylinder engine actually exceeds some small blocks from the first muscle car era.
Before the first aluminum block was cast, the new Pentastar V-6 benefited from more than 45,000 hours of computer analysis to optimize the design of the engine. Once assembled, the engines were thoroughly tested and evaluated on dynamometers and in vehicles. More than 12 million customer equivalent miles were logged on the dynos followed by vehicle testing of nearly 4 million customer equivalent miles. In addition, a test batch of engines were made in February 2009, and sent to Roush Industries (which preps Challenger drag cars) for extensive hot testing, to find any problems before customers.
The Pentastar engines have an open deck design, with four oil return holes below the head bolt holes. The open deck makes manufacturing cheaper, at the cost of upper cylinder support. There have been numerous open deck engines in Chrysler’s history, including the aluminum 225 cid. slant six and the current four-cylinders.
The 60-degree 3.6-liter Pentastar 24-valve dual overhead cam engine is compact and lightweight, with a total length of 503 mm (94mm shorter than the 3.7 and 34 mm shorter than the 3.5). This relieves packaging constraints, allowing more power or smaller engine bays.
Bore and stroke measure 96mm by 83mm. The block is a high-pressure, die cast aluminum unit with cast iron bore liners and aluminum cylinder heads; cast aluminumpistons with low friction rings are fitted to forged steel connecting rods. Pistons have a reduced skirt area to cut weight and friction. Compression ratio for the engine is 10.2:1 for all applications. Piston cooling jets are fitted to each cylinder, spraying oil onto the piston to prevent detonation, control heat, and allow MDS in the future.
The nodular iron crankshaft is common to all Pentastar engines. It has an 83% increase in fatigue strength due to the rolled fillet process. The crankshaft has four bolts on the main bearing supports; two more are cross-fitted in the main bearing caps providing an extremely rigid bottom end. A structural windage tray reduces oil splash on the crankshaft and cuts power losses from the reciprocating assembly, while increasing structural stiffness and lowering engine noise.
Four powdered metal main bearing caps are used; they are cross-bolted, with directional arrows molded in. Two-piece upper half thrust bearings at located at the #2 main bearing; they are installed with the oil groves facing outward. The main bearing caps are a cross-bolted, 6-bolt design. Three oil drain back drillings are on each of the cylinder banks, and two knock sensors are in the block valley.
The engine accessories have no brackets; they are bolted directly to the block, cutting vibration. Since the air conditioner compressor and alternator are both bolted to the block, a tensioner is used with the serpentine belt to maintain appropriate tension. The Phoenix engine was designed to be used in either a North-South and East-West configuration.
Refinement was achieved with the help of advanced computer-aided engineering. Structural, intake, and exhaust areas deliver low levels of noise.
Intake and Exhaust
Cylinder heads are constructed of T7 heat treated aluminum and feature dual overhead camshafts with roller finger followers. On the intake side, valve diameters are 39mm with 17 degrees relative to the bore axis. Exhaust valves are 30mm in diameter and canted at 18.8 degrees. Combustion chamber volume is 52.7cc.
Independent cam phasing also is used on all four camshafts. Torque actuated, the phasers use the natural action of the valve springs to pump the phasers into position, lowering the amount of energy required to move the phasers very quickly. The small size of the phasers combines to reduce weight and allows the camshafts to be spaced very closely together for optimum valve angles and combustion chamber geometry.
Induction is handled through a multi-point port fuel injection system and a lightweight composite intake manifold. Throttle bore diameter is 74mm. Both the intake and exhaust systems have been designed to provide efficient flow characteristics with a minimum amount of restriction in the passages. On the exhaust side, spent gases exit through an integral exhaust manifold that is cast into the cylinder head- unique in the Chrysler engine line-up.
The integral exhaust manifold eliminates the need for separate cast iron or steel exhaust manifolds and contributes to improvements in engine refinement and weight. The integral manifold also results in a broader range of stoichiometric operation reducing fuel consumption during mountain grade and trailer tow driving.
Extremely efficient with advanced emission technology, the new 3.6-liter Pentastar was designed for all future emission standards. This required no Exhaust Gas Recirculation (EGR) and helped reduce the mass of the engine. The engine also was been designed to meet all known future worldwide emission standards, including LEV III and PZEV California standards. For export applications, the Pentastar V-6 is capable of meeting Euro6 standards.
Despite its 10.2:1 compression, the engine is designed to run on regular unleaded fuel with an octane rating of 87. The engine also can run on E85 blended gasoline.
Ports and Manifolds
The engine features high-flow intake and exhaust ports, which in combination with dual independent cam phasing, allows optimum volumetric and combustion efficiency over the full speed and load range. This results in an exceptional, flat torque curve along with high specific power.
The intake valve is a single-piece design, made of forged heat resistant (martensitic) steel; exhaust valves are two-piece designs, with a forged austenitic head welded to a martensitic stem, and both have a nitrided surface treatment to prevent scuffing (except at the tip and lock grooves). Roller rocker arms, pivoting on stationary lash adjusters, activate the valves, which use three bead lock keepers to help rotation and retain the springs.
The timing drive uses four chains, each of which is a “silent chain link” design to improve sprocket engagement and cut noise, vibration and harshness (NVH). One chain, with a spring-loaded tensioner, drives the oil pump and three drive the camshafts. Primary and secondary camshaft chains use oil pressure controlled chain tensioners; the left secondary uses a ratchet, the right secondary and primary do not. Chain guides and tensioner arms alike are made of glass-filled nylon, with nylon wear faces.
The cylinder heads are made of aluminum, with unique left and right castings and integrated exhaust manifolds. The valves have pressed-in powdered metal guides, which are not serviceable. The valve train uses roller rocker arms with hydraulic lifters. Spark plug tubes are pressed into the heads and sealed in place; the tubes have thin walls.
The advanced oil filter system eliminates oil spills, thanks to an incinerable filter element instead of the typical spin-on filters; the filter is conveniently located on top of the engine.
A chain-driven, vane-type variable displacement oil pump adjusts the flow rate and pressure as commanded by the engine management system, which uses a solenoid to drive the pump into low or high pressure mode. For example, below 3,500 rpm, the pump conserves energy by using low pressure; at speeds over 3,500 rpm, the pump switches to high pressure.
A force balance mechanism inside the oil pump adjusts the size of the pumping chambers to alter oil flow. If the oil is cold, the pump reduces the size of the internal chambers. When the oil is hot and thinner, more oil is needed, and a spring increases the size of the pump chambers. This also saves energy.
The pump is driven at a 1:1 drive ratio; its location under the block is more efficient than an on-crankshaft location. An internal, mechanical ball-and-spring relief valve dumps oil into the sump when needed, for conditions such as a cold start with high engine speed. Both pump and pressure regulation solenoid are non-serviceable.
The engine takes six quarts of conventional 5W-30 oil (with an ILSAC standard of GF5). The standard change interval, with this oil, is 8,000 miles under normal driving conditions.
The oil pick-up tube is supported at the windage tray. Three oil gallery plugs are in the engine block; oil pressure an be monitored with a scan tool. Oil pressure and temperature sensors are on the oil filter housing assembly, which is mounted on top, between the heads; the oil cooler (a plate-style coolant to oil heat exchanger) is mounted to the oil filter housing as well.
The Trenton Engine Plant manufactures an upgraded version of the 3.6L V6. It has variable valve lift, liquid cooled EGR, low-friction timing set components, for efficiency and lower emissions. It was released in 2016 and is used in 2016-present Jeep Grand Cherokee, 2016-present Dodge Durango, 2016-present Chrysler Pacifica, 2020-present Chrysler Voyager, 2018-present Jeep Wrangler Unlimited JL, and 2020-present Jeep Gladiator (JT).
The upgraded 3.6L is rated at 295 hp and 260 lb⋅ft. This is due to a different intake/exhaust layout.