Willie Racine's Jeep

Pentastar Reshaped for '12 Wrangler

By Eric Mayne WardsAuto.com, Sep 1, 2011 8:52 AM

PORTLAND, OR ? Chrysler's celebrated Pentastar 3.6L V-6 came up a little short when engineers first pondered how well it would function in the '12 Jeep Wrangler.

Designed for plug-and-play application across the Chrysler portfolio, the engine's alternator is located on a plane near its midpoint.

"Our issue was, that's down by our water line," says Ray Durham, vehicle line executive-SUV, referring to the 30-in. (76-cm) water-fording capability required of all Wranglers because all models boast the Jeep brand's rugged Trail Rated designation.

So the alternator was raised. But the changes did not stop there.

Chrysler engineers have leveraged the Pentastar's adaptable design to make additional changes exclusive to the Wrangler, the 12th of 13 promised near-term applications of the V-6, which bowed on the '11 Jeep Grand Cherokee and earned a spot among Ward's 10 Best Engines for 2011.

"We wanted a flatter torque curve on the bottom end, which helps the drivability off-road," Durham tells WardsAuto at a media preview here.

A 10% bump in peak torque to 260 lb.-ft (353 Nm) augments the engine's 285-hp output rating, a 40% jump from the outgoing 3.8L V-6.

But on-road refinement, a longstanding Wrangler sore point, was an even greater priority. This led to an overhaul of the intake system; the manifold and intake-runner tuning are exclusive to the '12 Wrangler.

Acoustic cover on new Wrangler engine designed to dull NVH.

Even the system's location is unique. Induction is accommodated through a revamped throttle body on the engine's left side.

The intake system is on the right side for all other Pentastar applications.

Further enhancing the '12 Wrangler driving experience is the accelerator pedal, Durham says. The actuator has been tuned to provide improved feedback.

An acoustic cover tops off the Wrangler-only Pentastar features. Chrysler says it boosts the SUV's refinement by reducing engine noise, vibration and harshness ? issues the auto maker tackled in earnest when it upgraded the '11-model's interior.

"The transmission plays as big a factor for improved NVH levels," Durham notes.

For model-year '12, the Wrangler benefits from its first-ever 5-speed automatic transmission, the A580 originally was designed to mate with Chrysler's legendary 5.7L Hemi V-8.

Equipped with the optional A580, which is expected to account for 80% of the Wrangler's volume, gear-hunting "has virtually disappeared," Durham claims.

The standard-equipment gearbox is the NSG 370 6-speed manual, the first 6-speed manual to be mated to the Pentastar.

Chrysler says both transmissions will enable the '12 Wrangler to achieve a highway-cycle fuel-economy rating of 21 mpg (11.2 L/100 km), an improvement from '11 Wrangler's 19-mpg (12.4-L/100 km) performance.

The 4-door Wrangler Unlimited slips to 20 mpg (11.6 L/100 km) with the 5-speed gearbox.

With either transmission, expect city-cycle performance of 16 mpg (14.7 L/100 km) and 17 mpg (13.8 L/100 km), respectively, from the Wrangler Unlimited and the Wrangler, the auto maker says.

On the emissions side, the Pentastar-equipped Wrangler meets U.S. Tier 2 BIN 5 emission requirements and Ultra-low Emissions Vehicle II standards, in addition to California's LEV III and PZEV regulations and "all known future" benchmarks worldwide, Chrysler says.

The Pentastar's plug-and-play design accommodates front- and rear-wheel-drive architectures in midsize and large segment ranges.