Published July 11, 2012
By Jeff Cobb
As you may know, automakers are increasing their arsenal of engineering tricks to get fuel efficiency gains where possible, and perhaps the latest is diamond-like coatings (DLC) used on piston rings by Chevrolet.
The super hard coating on steel piston rings in the Sonic and Cruze allows engineers to specify less spring tension for sealing purposes, and the rings are said to reduce friction for an incremental gain in fuel efficiency, while also enhancing longevity.
General Motors says in validating DLC-treated rings, it has “cracked the code” for this surface treatment chemistry used also in a variety of items including computer hard drives, semi-conductors and orthopedic implants.
“Depending on its intended use, diamond-like carbon coating can be chemically engineered to resist wear, control friction or avoid adhesion,” says GM. “In industrial applications, such as those being tested at a GM powertrain facility, a specially formulated DLC coating on metal hole-drilling tools helps avoid aluminum adhesion that can ‘gum up’ machinery and cause production delays.“
Without saying precisely how much the DLC contributes to bottom line mpg figures, GM does credit it toward helping the Ecotec 1.4-liter turbo engine and six-speed transmission in the Sonic deliver 29 city and 40 mpg highway as it does also for the Cruze rated at 26 city and 38 highway.
“Through years of lab research, we’ve acquired an understanding of how to work with DLC at the atomic level,” said Michael Lukitsch, GM senior researcher. “It holds great promise for future applications, both in advanced manufacturing processes and improved production parts that save our customers money.”
Next up on the agenda for fractional gains in efficiency could be as soon as 2014 when GM may begin treating other powertrain components such as rocker arms with the DLC formula.
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