2011 Pentastar is Chrysler's new do-it-all V6

  • 15-Dec-2010 03:49 EST
PentastarV6 - Lead Image - FINAL.jpg

New Pentastar V6 is more package-efficient than the old DOHC and SOHC V6s it replaces. Note dual cam phasers, integrated exhaust manifold/cylinder head casting, and reinforced nylon cam covers and intake module on this factory cutaway.

Turning Chrysler into a cost-effective manufacturer that can produce competitive vehicles is a job that is being attacked on many fronts. One of the most important engineering steps toward that goal is the recent introduction of the 3.6-L Pentastar V6.

Why can one new engine make a big difference? After all, almost every other automaker has a DOHC V6 in the 3.5-4.0-L displacement class, and in many cases it has enabled a phase out of a pair of older engines. At Chrysler, however, the new V6 is putting seven incumbent V6 engines (six in domestic use) into retirement. The considerable savings from reduced bill of materials and manufacturing complexity is a key part of the strategy, of course.

Instead of 189 major components for seven "legacy" V6s being discontinued, Chrysler now needs just 32 for all current variants of the 3.6-L V6. A major contribution is made by eliminating separate exhaust manifolds—they’re integrated with the Pentastar cylinder heads. Formerly 32 exhaust manifolds had been required for the seven obsoleted engines.

Likewise, just two intake manifolds (each with upper and lower sections) are specified for the new Pentastar V6—four total parts, not including fasteners, for Pentastar vs. 32 parts for its seven predecessors.

Even as Chrysler adds Pentastar variants, including versions with smaller cylinder displacement and engineering features needed to meet tightening fuel economy standards, the total bill of materials for the Pentastar family is expected to remain a fraction of the 2010 number for the seven retirees.

The single-V6 strategy offers many other benefits, including the promise of higher quality, the ability to upgrade for new vehicle applications more efficiently, reduced service complexity, and lower warranty expense.

The Pentastar engine program began during Daimler's ownership of Chrysler. The program went on hiatus when Cerberus Capital Management became Chrysler's next owner and began looking at alternatives. The V6 effort appeared to sputter, as Chrysler's engineering manpower was stretched ever thinner under Cerberus and the economic recession. But development was ultimately restarted, finished, and the engine brought into production during 2010 by the Chrysler engineering team.  

Besides replacing the patch quilt of obviously dated V6s in the company's engine portfolio, Pentastar was designed with the highest possible level of flexibility for much of the Chrysler product lineup—present and future. It will likely see some applications for new parent Fiat as well.

Technical features

The DOHC aluminum engine will be initially made in four closely related variants. One develops a claimed 283 hp (211 kW) for transverse front-drive applications. The rear-drive version produces a claimed 290 hp (216 kW), and the one developed for all-wheel-drive use is rated at 292 hp (218 kW).

A fourth, high-performance variant offers the magic “over 300” number – 305 hp (227 kw) to be specific, for use in the rear-drive Dodge Challenger. That horsepower rating is SAE-certified on regular 87-octane gasoline. It also is capable of running on E85.

The cylinder blocks configured for transverse and longitudinal applications are architecturally similar. Each incorporates a structural windage tray and oil-cooling jets aimed at the undersides of the piston crowns. There are just two cylinder heads covering all variants. Engine internals are exactly the same, including the camshafts and pistons.

The valvetrain features camshaft phasing on intake and exhaust. Rolling-element valve lifters help reduce friction.

The Pentastar V6s are shorter in height than the various overhead-cam engines they replace. This improves powertrain package efficiency and helps expand the Pentastar's potential applications within the future Chrysler and Fiat vehicle portfolios.

Much design-engineering focus went into routing the intake and exhaust systems to optimize output. (Because the present variants are internally the same, horsepower differences between north/south and transverse applications are strictly due to routing and shape of intake and exhaust systems, and software calibrations.) In the case of the Challenger, a more aggressively designed intake air system is the enabler for the 13-hp (9.7-kW) increase vs. the other longitudinal fitments, allowing an airflow increase from 214 to 220 g/s.

Bore and stroke of the 3.6-L Pentastar V6 measure 96 x 83 mm, and Chrysler engineers are working on other displacements for the future, including a reported 3.0-L turbocharged version. The Pentastar architecture was protected for the future addition of other technologies Chrysler engineers and product planners deem necessary to keep the engine competitive. The systems include direct fuel injection and cylinder deactivation (Chrysler's MDS, or Multiple Displacement System as currently used on the 5.7-L Hemi V8).

Fiat’s Multi-Air system also is being investigated for use on the Pentastar family. Extensively reported in AEI, Multi-Air uses electro-hydraulic actuators to vary valve lift and timing and deliver intake valve throttling (instead of using a throttle plate). One operating stage of Multi-Air effectively equals cylinder deactivation. Multi-Air can be incorporated into gasoline engines with both direct injection and turbocharging and also can be used on diesels.

A variable-displacement oil pump with a computer-actuated flow-pressure control valve is one key contributor to Pentastar's projected improvement in fuel efficiency, compared with the outgoing V6s. The pump's displacement is reduced when the lubricating oil is cold and thick and increased when it's hot and thin. Pressure and flow are reduced below 3500 rpm.

The new V6 is built on a new line at Chrysler's Trenton, MI, plant. Some of the advanced technologies (and new vehicle applications) are coming in 2012, when a second plant under construction in Mexico is due to come on stream. The two production lines will be virtual twins, each with a capacity of about 440,000 engines. Volume is expected to ramp up sharply in calendar year 2012. 

The introduction of Fiat Group vehicles may add a new look to the Chrysler lineup, as well as a new mix of powertrains. The 2011 Chrysler and Dodge sedans with the base 2.4-L four-cylinder “world engine” have been refreshed, and for options they’ll take some of the Pentastar production. But for the vehicles Chrysler sells in volume—Jeeps, minivans, and soon pickups as well—the new V6 is expected to be the prime mover.

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