FCA has upgraded its 3.6-liter Pentastar engine for MY 2016. The 3.6L Pentastar, first introduced in 2009 (earlier post), was the first of an all-new line of V-6 engines intended to improve fuel efficiency across the Chrysler, Jeep and Dodge lineup. More than 5 million Penetastar engines are now on the road.
Depending on the application, the redesigned V-6 delivers fuel-economy improvements of more than 6% while increasing torque more than 14.9%. This occurs at engine speeds below 3,000 rpm, where elevated torque has its most profound impact on the driving experience. Enhancements such as two-step variable valve lift (VVL), cooled exhaust-gas recirculation (EGR) and innovative weight-reduction strategies boost the engine’s efficiency and performance, all while preserving its smoothness.
Increased fuel-efficiency was a key impetus in the development of the redesigned 3.6-liter Pentastar V-6 engine. FCA US LLC powertrain engineers evaluated multiple technologies, accumulating more than 4.7 million customer-equivalent miles using computer simulation and physical tests.
The most compelling enhancement is two-step variable valve lift (VVL). The system is designed to remain mostly in low-lift mode until the customer demands more power; then it responds by switching to high-lift mode for improved combustion.
The result is less overall pumping work, which on its own, accounts for a fuel-economy improvement of up to 2.7%, compared with the 3.6-liter Pentastar’s previous iteration, named three times to the annual Ward’s 10 Best Engines list.
The addition of cooled EGR, in addition to the obvious emissions-reduction benefits, further cuts pumping losses and enables knock-free operation at higher, real-world loads. This translates to a fuel-economy improvement, on its own, of up to 0.8%.
|3.6-liter Pentastar V-6 adds cooled EGR for model-year 2016. Click to enlarge.
Pumping losses are again targeted with the engine’s upgraded Variable Valve Timing (VVT) system. For 2016, it moves to torque-driven cam-phasing, which reduces oil demand. The new VVT system also increases its range of authority to 70 degrees, from 50 degrees. This helps mitigate knock during hot starts and expands the operating envelope of Engine Stop Start (ESS), a fuel-saving feature that is carried over from the previous-generation 3.6-liter Pentastar.
ESS is driven by a high-speed/high-durability starter that reduces crank time for quicker restarts. The system is regulated by algorithms which act on the vehicle’s powertrain and chassis components.
As a result, acceleration is always aligned with driver inputs. Passive accelerator application is met with measured throttle response; hard inputs trigger aggressive starts.
More torque is also delivered more quickly by recalibrating the VVT system to leverage the benefits of the new intake manifold’s longer runners. The result is a torque boost of more than 14.9%, depending on the vehicle application, between 1,000 and 3,000 rpm.
Combustion upgrades. The redesigned 3.6-liter Pentastar V-6 also engine benefits from numerous upgrades which better harness the combustion event. Most notably, the engine’s compression ratio jumps to 11.3:1 from 10.2:1, compared with the engine’s previous iteration.
High-tumble intake ports combine with shrouded valves to take advantage of the engine’s new fuel injectors. Featuring eight holes each—twice the number in the previous iteration’s injectors—they offer optimized atomization and targeting.
Combined with 100-millijoule high-energy ignition coils with platinum sparkplugs, the above combustion enhancements account for a 1.5% improvement in fuel economy.
Multiple friction-reduction strategies contribute to an additional 1% fuel-economy hike, compared with the engine’s previous iteration. Particularly notable is the use of HG-R1 on the timing drive guide-faces. The new Pentastar is the first production engine to feature this low-friction material.
Also contributing to friction reduction are new valve springs, low-tension piston rings and piston pins which feature diamond-like carbon (DLC) coating.
Form. An integrated exhaust manifold contributes to packaging efficiencies that enable plug-and-play-type integration across a range of vehicle segments and drivetrain configurations.
The new 3.6-liter Pentastar debuts on the 2016 Jeep Grand Cherokee. The new intake manifold improves airflow, which benefits volumetric efficiency and enables a boost of up to 295 horsepower (220 kW), from 290 horsepower (216 kW).
For model-year 2016, FCA US powertrain engineers were challenged by the potential negative effects of incremental weight wrought by the engine’s new feature content. However, clever component redesign produced an engine that weighs as little as 326 pounds (148 kg), depending on the application—four pounds less than the previous 3.6-liter Pentastar, despite the addition of new content weighing 13 pounds.
A thin-wall strategy was used to reduce the nominal thickness of certain die-cast components , without compromising noise, vibration and harshness (NVH) characteristics.
Windage-tray weight was slashed by 19% and front-cover weight was cut by 5%. Two-piece oil pans were eliminated, with the exception of Trail Rated vehicles.
The crankshaft main bearings and pins were trimmed, which contributed to an overall block-assembly weight reduction of 6 lbs (2.7 kg). This generates additional friction-reduction.
For model-year 2016, FCA US engines—except for the 8.4-liter V-10 that powers the Dodge SRT Viper—will be E15-compatible in anticipation of the fuel’s proliferation.