Back when a greenhouse was a structure used to grow plants in cold weather, an oil pump was just a non-descript but necessary device to keep metal engine parts well lubricated. As engineers work to meet the 35.5 mile per gallon Corporate Average Fuel Economy (CAFE) standard, the lowly oil pump has become one of many places where they can find incremental improvements in efficiency.

The turbocharged 1.4-liter inline-four in the 2011 Chevrolet Cruze features a variable displacement oil pump that helps reduce the parasitic losses that increase fuel consumption. While an engine always needs oil, the amount depends on the speed and load at any given time. Traditional oil pumps are driven off the engine and sized for the worst case conditions the engine is expected to experience. As a result, they typically move much more oil than the engine needs, and the excess is dumped back to the oil pan through a bypass.

The variable displacement pump on the Cruze engine is electronically controlled so that it only sends out as much oil as the engine needs. Spring-loaded vanes sit in slots in the drive hub of the pump as it rotates in an off-center housing. As the hub rotates from the pump inlet to the outlet, the vanes are pushed in and the cavity between them gets smaller causing the oil pressure to rise. A larger difference between the inlet and outlet volume means more oil pressure and flow.

The outer housing of the General Motors pump is mounted on a pivot, which allows the center of the housing to move closer to the center of the hub. This reduces the volume change in the pump and the resulting oil flow.

According to GM spokesman Tom Read, the efficiency improvement attributable directly to the new oil pump is "less than one percent." However, when added together with other, similar features like thermostatic shutters that close off the grille at higher speeds and the electric power assisted steering, it adds up to a car that gets an EPA rating of 40 miles per gallon on the highway.

[Source: General Motors]



PRESS RELEASE

Special Oil Pump Helps Chevrolet Cruze Conserve Fuel
Variable Displacement Pump Delivers Precise Amount of Oil in all Driving Conditions

2010-08-25

PONTIAC, Mich. – The oil pump in the engine of the 2011 Chevrolet Cruze takes a laid-back approach to its work, delivering the precise amount of oil needed during all driving conditions. That requires the engine to work less versus a conventional pump and ultimately saves fuel.

A standard feature in the Cruze's Ecotec 1.4L turbocharged engine, the variable displacement oil pump reduces the displacement during engine warm up and high speed conditions. The volume of oil from the pump varies with rpm by changing the pump's displacement through a pivoting control chamber mechanism and sliding vanes. A fixed displacement pump would typically bypass the extra oil internally.

"By lowering the volume of oil we reduce the amount of energy, or torque, required to pump the oil, without taking necessary lubrication away from the engine," said Mike Katerberg, assistant chief engineer for the 1.4L. "Reducing the torque demand reduces fuel consumption. It's a simple, durable, maintenance-free design that we have used in our transmissions for years and more recently in our hybrid vehicles."

The Ecotec 1.4L turbo is standard on Eco, LT and LTZ models and helps the Cruze Eco, with a standard six-speed transmission, achieve an expected segment-leading estimated 40 mpg on the highway.

The benefits of the variable displacement oil pump increase when used with other technologies such as variable valve timing which operate using oil pressure. Variable valve timing adjusts the engine valves' opening and closing timing for optimal performance, fuel efficiency and emissions across the rpm band – including greater low-rpm torque.

The all-new 2011 Chevrolet Cruze will begin arriving in U.S. dealerships this September, starting at $16,995, including destination. Priced to compete in the compact-car segment, the Cruze offers more interior room, more miles per gallon in the Eco model, and more standard safety features than any of its competitors.

About Chevrolet

Chevrolet is a global automotive brand, with annual sales of about 3.5 million vehicles in more than 130 countries. Chevrolet provides consumers with fuel-efficient, safe and reliable vehicles that deliver high quality, expressive design, spirited performance and value. In the U.S., the Chevrolet portfolio includes: iconic performance cars, such as Corvette and Camaro; dependable, long lasting pickups and SUVs, such as Silverado and Suburban; and award-winning passenger cars and crossovers, such as Malibu, Equinox and Traverse. Chevrolet also offers "gas-friendly" solutions, such as the upcoming 2011 Chevrolet Cruze Eco model that is expected to deliver up to an estimated 40 mpg highway, and 2011 Chevrolet Volt that will offer up to 40 miles of electric driving and an additional 300 miles of extended range with the onboard generator (based on GM testing). Most new Chevrolet models offer OnStar safety, security, and convenience technologies including OnStar Hands-Free Calling, Automatic Crash Response, and Stolen Vehicle Slowdown. More information regarding Chevrolet models, fuel solutions, and OnStar availability can be found at www.chevrolet.com.

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