Thread revival:
More detailed article posted about the noise cancellation / MPG interaction, this time for the GMC Terrain crossover (badge sibling of the Equinox):
(Note: EPA-rated 32 mpg (US) highway )
Quote:
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When GM engineers set out to deliver segment-leading fuel economy on Terrain they chose to lower the 6-speed transmission's gear shift points to enable the Ecotec 2.4L four-cylinder engine to run at lower rpm torque. In this "Eco" mode, which the driver can activate with a click of a button on the console, the torque converter clutch engages at lower engine speeds to help save gas. While the engineering action improved fuel efficiency by up to one mpg, it also created an objectionable low-end frequency boom. To counteract that boom the engineers turned to active noise cancellation technology.
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source:
High-End Audio Technology Helps Terrain Get Top MPGs -- DETROIT, Feb. 22, 2011 /PRNewswire/ --
(Article outlines other ecomods to the vehicle to boost MPG.)