General Motors Corp.: 6.0L OHV V-8 Hybrid

GM widens the hybrid landscape with its world-first 2-Mode system, bringing HEV technology to fullsize SUVs.

Bill Visnic

January 2, 2008

3 Min Read
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Ward’s 10 Best Engines

Look out the window and check to see if pigs are flying. That’s what we figured would happen before any 3-ton GMC Yukon SUV achieved 20 mpg (11.8 L/100 km) in city driving.

Yet that’s the powertrain near-miracle delivered by General Motors Corp.’s all-new 2-Mode hybrid-electric system, essentially an electronic continuously variable transmission (CVT) augmented by two electric motors, fixed-gear capability and a highly optimized, 6.0L variant of GM’s small-block V-8. The breakthrough, of course, is that city economy of 20 mpg – 21 mpg (11.2 L/100 km) for 2-wheel-drive models – is a 50% leap over the same vehicle powered only by a 5.3L V-8.

GM boasts the Yukon Hybrid is as efficient in city driving as a 4-cyl. Toyota Camry. The company long has said it believes hybrid-electric vehicle technology, initially at least, is best suited for the industry’s thirstiest vehicles, where the efficiency enhancement makes the most impact. The 2-Mode design, in fact, is an extension of the system first developed for mass-transit buses.

The automotive 2-Mode system was developed in cooperation with the former DaimlerChrysler AG and BMW AG. Chrysler LLC, Daimler and BMW also plan soon to release hybrid models using the 2-Mode design.

But it’s GM that gets to market first with the GMC Yukon Hybrid, along with the same setup for Chevrolet’s Tahoe fullsize SUV.

And this is no mere feel-good public-relations effort: The 2-Mode system is the first to bring hybridization to the fullsize utility-vehicle segment, and the technology has big implications for smaller, unibody platforms, too.

And for those who want to make the hybrid statement but still need the option to tow as much as 6,200 lbs. (2,812 kg), there is no other vehicle in the market.

The Yukon Hybrid’s fuel-economy figures seem realistic, too – a problem prior hybrid technology has been forced to overcome.

Several Ward’s 10 Best Engines testers achieved mixed-driving averages of 19 mpg (12.4 L/100 km) or so. That’s pretty impressive for such a heavy vehicle being hauled by a 332-hp V-8. And everyone praises the fine integration of the 6.0L V-8 and the CVT 2-Mode.

“None of the annoying jerk-and-pull of typical hybrid transitions,” says one editor. “Enough electronic sophistication for a mission to Mars,” says another. And every judge awarded maximum points for technical relevance, saying this easily is the most technically significant powertrain introduced this year.

OK, we’re not blown away by the roughly 10% fuel-economy improvement in highway driving. Early information had hyped the 2-Mode’s advantages over “conventional” HEVs that deliver virtually no improvement in highway-driving efficiency. We frankly were hoping for more.

And no matter how you spin it, this system isn’t cheap: The buy-in point is an eye-popping $50,490 for a 2WD Chevy Tahoe and tops out at $53,755 base price for a 4-wheel-drive Yukon Hybrid.

Even so, insiders say the company isn’t recovering the full cost of 2-Mode.

Caveats aside, GM’s 2-Mode system is a significant engineering achievement that has potential to propel hybrid technology to a new level of public and industry acceptance.

Ward’s 10 Best Engines is copyright Penton Media Inc. Commercial references to the program and/or awards are prohibited without prior permission of Ward’s Automotive Group.

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2008 10 Best Engines
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