Corvette Chief Engineer, Tadge Juechter (left) and Powertrain's, Sam Winegarden, address automotive media at the Bowling Green Assembly plant. Image: Author
© 2007 by Hib Halverson
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In researching our LS3 story, in late April of 2007, the CAC attended a media briefing staged at the Bowling Green Assembly Plant in conjunction with the C5/C6 Registry's "Birthday Bash" event.
Under President Bush's proposal, CAFE would go up 4% annually for seven years starting in 2010. By 2017, this would mean a little over 30% above the gas mileage of MY09 product. Right at our deadline, Congress passed a bill which, if signed into law, would mandate a 40% increase in CAFE by 2020. President Bush is expected to sign it. Regardless if it's 30 or 40%, the prospect of this has not only GM, but any manufacturer building cars for sale in the U.S. scrambling to assess product plans the next decade.
We asked Mr. Winegargen what his strategy would be to insure that an engine in a 2013 C7 would be capable of 12% better fuel economy while providing the performance and drivability Corvette customers expect.
The first technology he cited was cylinder deactivation which disables half the cylinders and is capable of useful fuel economy increases. GM already has this (called "Active Fuel Management" or "AFM") on some light truck engines and is introducing it in some 2008 passenger car engines.
AFM was once part of the C6 program, but at the stage of development it was early this decade, at the transition between eight and four cylinder operation, the system's interaction with the car's structure caused a harmonic vibration and noise problem. Back then, the only solution was to add a damper to the powertrain. That made for an unacceptable weight increase so the Chief Engineer at the time, David Hill, rejected AFM for C6.
Mr. Winegarden told the Corvette Action Center that since then, cylinder deactivation has been further developed, so "AFM" can now be implemented on Corvette without the weight increase.
The other technology Mr. Winegarden said may appear on a Corvette is direct injection. To date, GM has announced this on three different gasoline engines. Direct injection introduces fuel under very high pressure, directly into the combustion chamber rather than into the intake stream above the valve. This allows a higher compression ratio, which improves efficiency and that, in-turn, raises fuel economy.
Another idea which Mr. Winegarden did not mention, but which is already being used in GM's light truck engines, such as the L92, is a computer-controlled "cam phaser" which can alter camshaft phasing in a manner which can improve fuel economy at part throttle.
Some or all of these gas-saving engine features may appear early in the next decade as GM tries to the Corvette on the leading edge of performance and fuel economy in the high-sports market segment.