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Introduction
The 3.6L Pentastar V6 engine was first introduced in 2010 and developed to replace seven V6 engines in the Chrysler, Ram Truck, Jeep and Dodge ranges. Significantly, the Pentastar engine reduced the number of major engine components from 189 to 32, thereby simplifying the build process and achieving cost savings through purchasing efficiencies and a reduction in high cost parts. Within Australia, the 3.6L Pentastar V6 engine has powered the Chrysler LX2 300 (engine code: GCH), Jeep WK2 Grand Cherokee (engine code: ERB) and the Jeep JK Wrangler.
Key features of the 3.6L Pentastar V6 engine included its:
- High-pressure die-cast aluminium block with a 60-degree ‘V’ angle;
- Nodular iron crankshaft;
- Forged steel connecting rods;
- Cast aluminium alloy pistons;
- Semi-permanent mould cylinder head made from T7 aluminium;
- Double overhead camshafts (chain-driven);
- Variable intake and exhaust cam phasing over a range of 50 degrees;
- Four valves per cylinder actuated by roller finger followers;
- Port injection via four-hole injectors;
- Compression ratio of 10.2:1; and,
- Total length of 503 mm (34 mm shorter than the 3.5L EGG V6 engine in the Chrysler LX 300C).
Depending on application, the 3.6L V6 Pentastar engine weighed 150 to 153 kg (approximately 19 kg lighter than the 3.5L V6 engine in the Chrysler LX 300C).
For the Chrysler LX2 300, the 3.6L Pentastar V6 engine produced peak power and torque of 210 kW at 6350 rpm and 340 Nm at 4650 rpm, respectively. However, 90 per cent of peak torque was available from 1800 to 6350 rpm.
The Pentastar V6 engines are manufactured at three locations:
- Mack Avenue Engine Complex in Detroit, Michigan;
- Trenton Engine Plant in Trenton, Michigan; and,
- Saltillo South Engine Plant in Mexico.
While the Pentastar V6 engine was developed for technologies such as ‘Multiair’ (variable valve lift), direct injection and turbocharging, these were not offered on the 2010-16 3.6L Pentastar V6 engine. The post-2016 3.6L Pentastar V6 engine has been covered separately.
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| Model | Engine | Trans. | Peak power | Peak torque |
|---|---|---|---|---|
| Chrysler LX2 300 | 3.6-litre GCH petrol V6 | 8sp auto | 210kW at 6350rpm | 340Nm at 4650rpm |
| Jeep WK2 Grand Cherokee | 3.6-litre ERB petrol V6 | 5sp auto, 8sp auto |
210kW at 6350rpm | 347Nm at 4300rpm |
| Jeep JK Wrangler | 3.6-litre petrol V6 | 6sp man., 5sp auto |
209kW at 6350rpm | 347Nm at 4300rpm |
| Dodge JC Journey | 3.6-litre petrol V6 | 6sp auto | 206kW at 6350rpm | 342Nm at 4350rpm |
| Fiat JF Freemont | 3.6-litre petrol V6 | 6sp auto | 206kW at 6350rpm | 342Nm at 4350rpm |
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Block
The 3.6L Pentastar V6 engine had a high-pressure die-cast aluminium cylinder block with an open-deck design. The 3.6L Pentastar V6 engine had 96.0 mm bores and an 83.0 mm stroke for a capacity of 3604 cc. Within the bores, the Pentastar V6 engine had cast iron cylinder liners.
As a result of its high-pressure, die-cast manufacture, the Pentastar V6 engine had thin walls and the block itself weighed 35 kg (77 lbs). Relative to GM’s ‘Alloytec’ engines, it is estimated that the Pentastar block was around 9 kg (20 lbs) lighter, resulting in a saving on aluminium of around $40 USD per engine.
Due to its 60 degree ‘V’ angle, the 3.6L Pentastar V6 engine did not require balance shafts.
Crankshaft, connecting rods and pistons
The 3.6L Pentastar V6 engine had a nodular iron crankshaft that underwent a rolled fillet process. The crankshaft weighed 19.5 kg (43 lbs) and had four bolts on the main bearing supports, while two additional bolts were cross-fitted in the main bearing caps for a rigid bottom end. Specifications for the crankshaft were as follows:
- Main bearing cap material: powdered cast iron;
- Crankshaft journal width: 72 mm; and,
- Crank pin width: 59 mm.
A structural windage tray was used to reduce oil splash on the crankshaft and reduce power losses from the reciprocating assembly.
The 3.6L Pentastar V6 engine had forged steel connecting rods and cast aluminium alloy pistons which weighed 359 grams (+/- 5 grams). Attributes of the pistons included:
- Low-friction piston rings;
- Reduced skirt area;
- Full-floating piston pins with an offset of 0.8 mm; and,
- Three oil cooler jets mounted in the engine block which sprayed oil onto the pistons to reduce heat and suppress knocking tendencies. Each jet cooled two pistons and was attached to the main oil gallery.
Cylinder head and camshafts
The 3.6L Pentastar V6 engine had a semi-permanent mould cylinder head – made from T7 heat-treated aluminium – and chain-driven double overhead camshafts (DOHC). The chain drive of the 3.6L Pentastar V6 engine had four chains, each of which had a ‘silent chain link’ design to improve sprocket engagement and reduce noise. While one chain drove the oil pump, the other three chains drove the camshafts. The primary and secondary camshaft chains used oil pressure-controlled chain tensioners; while the left secondary used a ratchet, the right secondary chain and primary chain did not. The chain guides and tensioner arms were made of glass-filled nylon, with nylon wear faces.
The 3.6L Pentastar V6 engine had high-flow intake and exhaust ports, while the exhaust manifold was cast into the cylinder head. The integral exhaust manifold eliminated the need for separate cast iron or steel exhaust manifolds, thereby saving weight. The cylinder heads weighed 12.2 kg (27 lbs) without valves and 14.1 kg (31 lbs) with valves.
Cam phasing
The 3.6L Pentastar V6 engine had independent cam phasing for the intake and exhaust camshafts over a range of 50 degrees relative to the crankshaft. The torque-actuated phasers used the natural action of the valve springs to pump the phasers into position, lowering the amount of energy required to move the phasers. According to Chrysler, the small size of the phasers combined to reduce weight and allow the camshafts to be spaced closely together for optimum valve angles and combustion chamber geometry.
As per the valve timing table below, it is understood that the 3.6L Pentastar V6 had an intake duration of 260 degrees, exhaust duration of 251 degrees and 10 degrees of valve overlap.
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| Retard | Advance | ||
|---|---|---|---|
| Intake | Open | 2° ATDC | 48° BTDC |
| Close | 82° ABDC | 32° ABDC | |
| Exhaust | Open | 59° BBDC | 109° BBDC |
| Close | 12° ATDC | 38° BTDC |
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Valves
The 3.6L Pentastar V6 engine had four valves per cylinder that were actuated by roller finger followers with hydraulic lash adjusters. The single-piece intake valves were made from forged, heat-resistant (martensitic) steel, while the two-piece exhaust valves had a forged austenitic head that was welded to a martensitic stem. Both the intake and exhaust valves underwent a nitride surface treatment to prevent scuffing, with the exception of the tip and lock grooves.
Valve specifications for the 3.6L Pentastar V6 engine were as follows:
- Intake valve head diameter: 39 mm;
- Intake valve angle relative to the bore axis: 17 degrees;
- Exhaust valve head diameter: 30 mm;
- Exhaust valve angle relative to the bore axis: 18.8 degrees; and,
- Included valve angle: 35.8 degrees.
Intake
The 3.6L Pentastar V6 engine had a three-piece, composite intake manifold and a 74 mm throttle bore diameter. Since all 3.6L Pentastar V6 engine had the same internals, power differences between longitudinal and transverse applications are due to routing, the shape of the intake and exhaust systems, and software calibrations. It is understood that the maximum intake airflow for the standard output 3.6L Pentastar V6 engine was 214 g/s, though a higher-flow intake for the Dodge Challenger increased airflow to 220 g/s.
Instead of a mass airflow sensor, the Pentastar engine measured manifold absolute pressure (MAP), intake air temperature and oxygen, engine speed and valve timing – these inputs were then used in a speed-density algorithm to calculate the intake air volume.
Injection and ignition
The 3.6L Pentastar V6 engine had electronically-controlled, sequential fuel injection via four-hole injectors that were mounted in the intake port (i.e. ‘port injection’). The engine had coil-on-plug ignition via long-life spark plugs that were positioned in tubes that were pressed into the cylinder heads and sealed in place. The firing order for the Pentastar V6 engine was 1-2-3-4-5-6.
The 3.6L Pentastar V6 engine had a compression ratio of 10.2:1 and two knock sensors were positioned between the cylinder banks in the engine’s ‘V’.
Lubrication and PCV
The 3.6L Pentastar V6 engine had a variable displacement oil pump which adjusted its flow rate and pressure to minimise energy use. Specifically, the pump operated in a low pressure mode at engine speeds below 3500 rpm and a high-pressure mode beyond that. A spring mechanism inside the oil pump adjusted the size of the pumping chambers to deliver the required oil flow. Furthermore, the oil-filter system for the 3.6L Pentastar V6 engine eliminated oil spills and contained an incinerable filter element for easier disposal than conventional oil filters.
The 3.6L Pentastar V6 engine had a positive crankcase ventilation (PCV) system which used a camshaft-mounted centrifuge to separate oil from crankcase blow-by gases.
Emissions control
For emissions control, the 3.6L Pentastar V6 engine had dual three-way catalytic converters and heated oxygen sensors; the Pentastar V6 engine did not have exhaust gas recirculation (EGR).
