Pentastar V-6 Gets Enhanced Variable Valve Tech

Fiat Chrysler Automobiles NV has revamped its 3.6-liter Pentastar V-6 engine for the 2016 model year, making it more fuel efficient and more powerful than its predecessor. The engine also is slightly lighter and has improved NVH characteristics, according to the carmaker.

Depending on the application, the redesigned Pentastar V-6 is as much as 6% more fuel efficient and can provide nearly 15% more torque at engine speeds below 3,000 rpm, FCA says. In the Jeep Grand Cherokee, the engine's initial application, output has been increased to 295 hp from 290 hp.

Upgrades include changes to the valve system to reduce pumping losses and internal friction. This includes a new two-stage valve lift control system low lift to maximize efficiency during normal operation and high lift to improve combustion and enhance power as needed that generates a 2.7% gain in fuel efficiency, FCA says.

In addition, the operating range of the variable valve timing system has been increased 40%. This helps mitigate engine knock during hot starts and improves the operation of the stop-start system, which also benefits from a high-speed starter motor to reduce cranking time.

The use of lightweight components and other design elements shaves as much as 4 lbs off the engine despite adding 13 lbs of new content, FCA says. Weight-saving techniques include several thinner die-cast components and switching to a one-piece oil pan.

The engine also gets a cooled exhaust-gas recirculation system, which helps lower emissions and further cuts pumping losses. A new intake manifold with longer runners improves airflow and low-end torque.

Among other improvements are new cylinder heads with an 11.3:1 compression ratio (up from 10.2:1), platinum-tipped spark plugs, new valve springs, lightened crankshaft and crank pins and low-tension piston rings. The fuel-injection system features eight-hole ignition coils twice that of the outgoing engine to optimize atomization and targeting.

FCA chose to use an upgraded port-injection system instead of switching to direct injection, which the carmaker notes would have added cost and weight.