October 11, 2013 Update: 3.6L Pentastar Engine
Though it’s only a few years old, the Chrysler line of Pentastar V6 engines is quickly earning a place among the most durable and versatile powerplants in recent memory. After the successful debut of the 3.6L Pentastar V6 that is currently available in everything from the Dodge Challenger to the Ram 1500, Chrysler is rolling out a new 3.2L version that will power the 2014 Jeep Cherokee Trailhawk. After driving it off-road through the California hills, we decided to take a closer look.
The new 3.2L Pentastar V6 is very similar to its 3.6L bigger brother, but also differentiates itself in several key ways. With the introduction of the new 2014 Cherokee, Chrysler aimed to develop an engine that would make the crossover competitive when it comes to fuel economy, without losing off-road capability. That led to the 3.2L Pentastar V6, which makes 271 horsepower and 239 lb.-ft of torque while increasing fuel efficiency by 30% over the outgoing Patriot, to 19/28 MPG in the 4x2 Cherokee and 19/26 in the 4x4. Here’s how it works.
Just like the award-winning 3.6L, Chrysler’s new 3.2L Pentastar V6 engine sports a 60-degree, dual overhead cam design with an all-aluminum deep-skirt block. Also like the 3.6L, the 3.2L Pentastar features variable valve timing, lightweight forged steel connecting rods and eschews direct injection. Rather than pass the added cost of D.I. on to the consumer with minimal gains, the 3.2L Pentastar V6 in the 2014 Jeep Cherokee instead uses piston squirter jets to cool the combustion chamber.
Chrysler also maintained a key component in the Pentastar that helped it achieve its impressive combination of power and efficiency. Individual exhaust manifold runners are integrated directly with the aluminum cylinder heads, a testament to the automaker’s strategy to simplify. This innovative design allows exhaust gases to be cooled by the cylinder head water jackets (hat tip to Ward's here), easing stress on the catalysts and allowing the engine to work harder under demanding situations – like many Jeep owners are wont to experience.
However, there are two key differences in the 3.2L Pentastar V6, besides simply being smaller and more efficient.
One is that Chrysler has tweaked the oil pump for better performance. When the engine is running smoothly, the variable-displacement oil pump stays in low pressure mode all the way up to 3,500rpm. The original 3.6L Pentastar stayed in low only until 3,000. This creates less stress and consumption, while allowing the oil pump to kick into higher pressure when needed at higher speeds.
The other is that Chrysler changed the compression ratio to better suit the 2014 Jeep Cherokee. Remember, the new 3.2L Pentastar V6 is dealing with less power and a smaller package than the 3.6L. To ensure that it would still be capable of strong performance, Chrysler bumped the compression ratio up from 10.2:1 to 10.7:1. It’s another minor tweak to ensure that power is available without sacrificing in the way of fuel efficiency.
On a drive through steep inclines with loose gravel and huge dips, the 2014 Cherokee Trailhawk 4x4 had no problem putting that power down to the ground. More impressive was the consistency of the powerband to deliver across the entire rev range. Chrysler has a star in the P-Star, and the latest 3.2L V6 iteration only affirms that they’re on the right track.
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