Introduction
An evolution of the 2010 3.6L Pentastar V6 engine, the 2016 Pentastar V6 engine introduced a range of changes to reduce mass and friction, while increasing fuel efficiency and low-rev torque. Debuting in the 2016 Jeep Grand Cherokee, key features of the 2016 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 70 degrees (previously 50 degrees);
- Two-stage variable intake valve lift (new);
- Four valves per cylinder actuated by roller finger followers;
- Engine Start Stop system (new);
- Port injection via eight-hole injectors (previously four-hole injectors);
- Compression ratio of 11.3:1 (previously 10.2:1); and,
- Liquid-cooled exhaust gas recirculation (not previously included).
Relative to the2010 3.6L Pentastar V6 engine, mass reduction measures for the 2016 engine included:
- Slimmer reinforcement ribs for the cylinder block;
- Omission of the structural provision for the air pump (never used);
- Thin-wall castings for the cylinder heads, windage tray and front cover;
- A smaller oil pan (except for trail-rated Jeep applications);
- Reduced oil capacity (4.8 litres, previously 5.7 litres);
- Drilled holes in the front face of the water pump pulley;
- Crankshaft main bearings caps made from nodular cast iron (previously powdered cast iron);
- A recess in the head of the crankshaft damper retaining bolts; and,
- A lighter, two-piece intake manifold (previously three pieces).
As a result of these changes, the 2016 3.6L Pentastar V6 engine has a mass of 148-151 kg (around 1.8 kg less than the 2010 3.6L V6 Pentastar engine, despite features which added 6 kg or 13 lbs).
Furthermore, friction reduction measures introduced in the 2016 3.6L Pentastar V6 engine include:
- Narrower crankshaft journals (68 mm, previously 72 mm);
- Narrower crank pins (54 mm, previously 59 mm);
- Low-tension piston rings;
- Diamond-like carbon (DLC) coating for the piston pins;
- The use of HG-R1 (a low-friction plastic) on the timing drive guide-faces;
- Super-polish treatment for the valve train;
- Reduced valve spring loading; and,
- Revisions to the two-stage oil pump.
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. Due to its 60 degree ‘V’ angle, the 3.6L Pentastar V6 engine did not require balance shafts.
While the block of the 2010 Pentastar V6 engine weighed 35 kg (77 lbs), the post-2016 Pentastar engine was lighter again because of its slimmer reinforcement ribs.
Crankshaft, connecting rods and pistons
For the 2016 3.6L Pentastar V6 engine, the nodular iron crankshaft underwent additional fillet rolling for greater strength. The crankshaft 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: nodular cast iron (previously powdered cast iron);
- Crankshaft journal width: 68 mm (previously 72 mm); and,
- Crank pin width: 54 mm (previously 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.
For the 2016 3.6L Pentastar V6 engine, changes included the introduction of low-tension piston rings and a diamond-like carbon (DLC) coating for the piston pins.
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.
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.
Cam phasing
The 2016 3.6L Pentastar V6 engine had independent cam phasing for the intake and exhaust camshafts over a range of 70 degrees relative to the crankshaft, increased from 50 degrees for the 2010 3.6L Pentastar V6 engine. By increasing the range of adjustment, knocking tendencies could be suppressed during hot starts and the operating range of the Engine Stop Start (ESS) system expanded.
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.
Variable valve lift (VVL)
The 2016 3.6L Pentastar V6 engine introduced a two-step variable valve lift (VVL) system for the intake valves. The VVL system improved fuel economy by using the low-lift mode where power requirements allowed. According to Fiat Chrysler, the low-lift mode reduced pumping power draw and improved combustion, achieving a fuel economy improvement of up to 2.7 per cent depending on application.
Each roller cam follower incorporated a pivotable high-lift section that was held in place by a spring-loaded lock pin. On acceleration, a solenoid valve opened and oil pressure pushed against the lock pin to release the high-lift follower section. The high-lift section would pivot on a bushing and the roller follower would run on the low valve lift (5.75 mm) cam lobes. The low lift lobes would be used for engine speeds up to 2800 rpm, at which point the high lift (10.3 mm) lobes would be engaged.
Intake
The 3.6L Pentastar V6 engine had a lightweight, composite intake manifold and a 74 mm throttle bore diameter. For the 2016 3.6L V6 Pentastar engine, the intake manifold was a lighter two-piece design than its three-piece predecessor. Furthermore, the 2016 Pentastar V6 engine had longer intake runners for increased torque at low engine speeds and shrouded valves for enhanced air/fuel mixing.
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.
Engine Stop Start (ESS)
The 2016 3.6L Pentastar V6 engine had an ‘Engine Stop Start’ (ESS) system which enabled it to shut down when the vehicle was stationary in traffic to reduce fuel consumption. The engine control module (ECM) monitored engine speed and, when the vehicle came to rest, cut fuel flow to the cylinders and turned off the engine. While the engine was shut down, the larger batteries maintained other vehicle systems – such as air conditioning – so that passenger comfort was maintained. Within 0.3 seconds of the brake pedal being released, the engine automatically restarted and the transmission was engaged. To minimise crank time, the ESS system had a high-speed/high-durability starter motor.
Injection and ignition
The 3.6L Pentastar V6 engine had electronically-controlled, sequential fuel injection via injectors that were mounted in the intake port (i.e. ‘port injection’). For the 2016 3.6L Pentastar V6 engine, eight-hole injectors replaced the four-hole injectors of the 2010 Pentastar V6 engine for better fuel atomization.
The 3.6L Pentastar V6 engine had coil-on-plug ignition with high-energy (100 mJ) ignition coils and 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 2016 3.6L Pentastar V6 engine had a compression ratio of 11.3:1 (up from 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.
For the 2016 3.6L Pentastar V6 engine, oil capacity was reduced to 4.8 litres (previously 5.7 litres).
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
Like its predecessor, the 2016 3.6L Pentastar V6 engine had dual three-way catalytic converters and heated oxygen sensors. However, the 2016 Pentastar V6 engine introduced a liquid-cooled exhaust gas recirculation (EGR) system which reduced the temperature of the exhaust gases from 650 degrees Celsius to 130 degrees Celsius – this lower exhaust gas temperature enabled the higher compression ratio by suppressing knock at higher loads. According to Fiat Chrysler, the cooled EGR also contributed to a fuel economy improvement of up to 0.8 per cent.
