To hear Chrysler tell it, the automaker’s 3.6-liter Pentastar V-6 essentially will be a new engine when it makes its debut in the 2016 Jeep Grand Cherokee, its first application in the FCA lineup.
-Basic dimensional elements—bore, stroke, bore-center spacing—carry over, but the engineering team claims greater efficiency, improved torque characteristics, a small horsepower uptick, and better NVH performance.
-New components include new cylinder heads with an 11.3:1 compression ratio (up from 10.2:1), new eight-hole ignition coils, platinum-tipped spark plugs, new valve springs, low-tension piston rings, lightened crankshaft and crank pins, extensive friction reduction, and cooling of exhaust gas recirculation.
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However, the biggest single efficiency improvement, according to FCA engineers, is a revision to the engine’s variable valve timing, giving intake-side valves a two-stage lift strategy—low lift for routine power demands, high lift when the driver calls for more urgency.
-Operating range of the variable-valve-timing system has been increased from 50 to 70 degrees to mitigate detonation during hot starts, improving operation of the automatic engine stop-start (ESS) function. Carried forward from the current V-6, the ESS system has been enhanced with a new high-speed starter motor on order to reduce cranking time and deliver quicker, smoother starts.
-Conspicuous by its absence from the engine’s catalog of revisions is direct fuel injection. FCA chose to continue with an upgraded port-injection system, citing added cost and weight as tradeoffs that go with direct injection. (According to FCA, the new engine will weigh 326 pounds in the Grand Cherokee, four pounds less than the current V-6.) The engineers also looked at, and ultimately passed on, Fiat’s Multi-Air induction system, for reasons of cost and U.S. market suitability. While it would be nice to see DI (or even Multi-Air), this strategy gives FCA something in its pocket for future development of the engine.
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While FCA isn’t ready to deliver all the engine’s performance specifics, it did reveal that output in the Grand Cherokee advances from 290 to 295 horsepower. Torque is said to improve by “more than 14.9 percent” between 1000 and 3000 rpm. (Which would be . . . what? 14.91? 14.98? You’re getting ridiculously specific here, Chrysler.) Note that there was no mention of the maximum torque figure changing—it stood at 260 lb-ft in 2015—but the low-range boost will be welcome given that torque peaked at a rather lofty 4800 rpm. FCA also anticipates a fuel-economy boost of “more than six percent.” (So, 6.1?) That would translate to roughly 18 mpg city and just over 25 mpg highway.
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The revised 3.6-liter V-6 will be under the hood of the six-cylinder 2106 Grand Cherokee when it rolls into showrooms this fall. FCA is still mum on when it will spread to the rest of the lineup, but the 3.6-liter Pentastar currently appears in the Dodge Challenger, Charger, Grand Caravan, Journey, and Durango; the Chrysler 200, 300, and Town & Country; the Jeep Wrangler; and the Ram ProMaster, Ram Cargo Van, and Ram 1500 pickup.
-from Car and Driver Blog http://ift.tt/1UpeWRx
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