Just how will the refined 3.6-liter Pentastar V6 will enjoy six percent better fuel economy while delivering nearly 15 percent increased torque at low rpm? DCA engineers say a combination of 2-step variable valve lift (VVL), upgraded variable valve timing, improved intake ports and a new intake manifold will make it happen.
The basic architecture of the Pentastar–that is the physical dimensions and general design strategy–carry over, but nearly every internal part was massaged in some way, adding up to boost efficiency and power. The first sighting of the improved package will come in the 2016 Jeep Grand Cherokee, but numerous other DCA vehicles offer the upgraded V6.
The most compelling feature is the VVL (see above video). Working on the intake valves only, the system varies the valve lift from .230-inch at low speed to .410-inch when higher power demands are required. The lower lift reduces pumping losses, then at around 2,800 rpm the system switches to the high-lift lobe. It’s all activated by oil pressure and solenoid valves.
Complementing the variable lift are enhanced cam phasers that now operate based off engine torque (which reduces oil demand on the engine) and have an expanded range of authority from 50 degrees up to 70 degrees. A revamped cam-phasing strategy takes advantage of a redesigned intake manifold with longer intake runners, which help the low-end torque numbers.
Other changes include increasing the compression ratio from 10.2:1 to to 11.3:1, adding cooled EGR, reshaping the intake ports to add more tumble to the airflow and stepping up to 8-hole injectors for improved atomization. Friction losses were also addressed with low-tension oil rings, DLC-coated piston pins, new valve springs and the use of HG-R1 low-friction coating on the timing drive guide faces. Finally, even though many of the new features weighed a total of 13 pounds, the overall weight of the engine dropped four pounds.