GM's new 2.5-liter Ecotec four will be efficient and easy on the ear

By Editors on September 20, 2011 12:38 PM

More details are emerging about General Motor's all-new 2.5-liter Ecotec four-cylinder engine, and the latest heads-up involves how this bigger-and- better brother to the existing 2.4-liter will match excellent mileage-maxing skills with world-class levels of quietness and refinement. Set to launch next summer in non-ECO versions of the 2013 Chevrolet Malibu, this direct-injected, dual-overhead cam all-aluminum motivator is slated to deliver at least 190 horsepower and 180 lb-ft of torque. Matched with a six-speed automatic, it's also expected to deliver in excess of 30 mpg on the highway in the Malibu. But the news of the day involves the comprehensive efforts engineers made to reduce noise levels of this new "LCV" engine by 40 percent compared to the current Ecotec, and to more-precisely contour its sonic signature.

According to Tom Slopsema, Noise and Vibration engineer on the program, "No fastener, cover or internal engine part was left unexamined in our quest to make this an engine that surpasses the benchmarks in the industry." That was a formidable task, given the LCV's aluminum-intensive design and a variety of other mass-minimizing composite plastics. "Both (of those elements) are very effective radiators of noise, but their mass-saving advantages are a must for fuel economy," said Slopsema. "That meant we had to be more creative in how we approached noise reduction, addressing individual components' effects on overall noise and vibration.

The goal was to both cut noise in general and raise what couldn't be removed into a higher frequency range -- well above the 2,000-hertz level --where it becomes less intrusive to humans. That quest led the engineering team to target 10 fundamental elements for special attention. Internally, it resulted in this new-gen Ecotec engine using a stouter forged-steel crankshaft and iron main-bearing inserts, special camshaft drive chains and having its oil pump and dual balance shafts repositioned into a dedicated cradle in its two-piece aluminum and steel oil pan. External tweaks included things like a new acoustic manifold cover, structural cast-aluminum camshaft and balancer covers, plus an isolated fuel rail for the injection system which was carried over from the existing 2.4-liter.   

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