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USCAR Transmission Group and FEV propose new SAE standard for transfer case efficiency
3 March 2012
The Transmission Working Group (TWG) of the United States Council for Automotive Research LLC (USCAR) recently worked with FEV Inc. of Auburn Hills, Mich., to develop and propose a new SAE International standard to measure parasitic losses in transfer cases. The proposed standard is undergoing review by the SAE All-Wheel Drive Standards Committee with anticipated release by the end of this year.
USCAR’s TWG, the members of which include Chrysler Group LLC, Ford Motor Company and General Motors, contracted FEV Inc. in 2009 to conduct testing and data analysis that led to the proposed standard. FEV investigated losses in transfer cases with a two-fold goal of measuring efficiency of transfer cases in order to understand energy losses and accurately measuring those losses. Traditional methods did not provide accurate or consistent data.
The challenge was to develop a uniform, non-invasive transfer case test procedure, capable of yielding consistently accurate and repeatable data at various temperatures and speeds.
The efficiency of all driveline components must be quantified and understood before we can make improvements to benefit overall vehicle efficiency. While four-wheel drive offers substantial traction and handling improvements, and can be a vital safety feature in adverse weather conditions, its addition increases weight and energy loss, which degrade fuel economy. Our goal is to reduce these losses to improve fuel efficiency while maintaining the functional benefits of four-wheel drive.—Andreas Perakes, TWG member and four-wheel drive/driveline technical specialist at Ford Motor Company
The tests developed through the FEV contract deliver consistent data across cold, warm and hot temperatures and transmission output speeds ranging from 250-3500 rpm.
Disassembly is not required to implement these tests on the transfer case. The basic procedure requires each transfer case to begin the test at a target temperature of -7 °C. Once the target test temperature is reached, a series of data points are collected while the unit sweeps through a fixed speed range representative of typical vehicle speeds.
Key findings were presented during the 2011 SAE All-Wheel Drive Symposium, in a joint presentation between USCAR and FEV. Once released, the standard will be available through the SAE website.
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