New GM Hybrid coming soon..

ozpont · May 09, 2007, 08:04:04 AM

New Gm Hybrid is coming soon... and its a V8...!!...

Read on .. its worth keeping up with this stuff.. its NOT going away....

One System, Two Visions What to Do With an Electric-Drive System?
Tokyo's Answer Isn't the Same as Detroit's
May 7, 2007
Page D4 / WSJ 5/8

Toyota scored a coup with its Prius, a futuristic midsize car that uses a sophisticated electric-drive system to sip gas like a minicar. Now, General Motors is readying its response: a hulking V-8 powered sport-utility vehicle with a sophisticated electric booster that gives it the gas mileage of a minivan.

GM's "two-mode" hybrid gas-electric Chevrolet Tahoe and GMC Yukon trucks won't hit the market until late this year, or early next year. But last week, GM allowed journalists a sneak peek at prototypes of the vehicles, including a small amount of time behind the wheel.

The contrasting approaches to hybrid technology represented by the Tahoe and the Prius illustrate, quite dramatically, the different world views of GM and Toyota, which as of the first quarter of this year surpassed GM as the world's No. 1 seller of cars.

GM's Chevy Tahoe "two-mode" hybrid.
Toyota's "Hybrid Synergy Drive" system is designed primarily to reduce the petroleum consumption of relatively light vehicles operating in the city. That's what you'd expect from a company whose roots are in the small-car-dominated Asian market. Toyota's efforts to use its hybrid technology as a power booster for large cars and SUVs have produced so-so results, both in terms of fuel-economy improvement and sales.

GM, on the other hand, is a creature of the American heartland, where lots of people -- including lots of GM employees -- want vehicles that can comfortably haul up to seven people, their gear and a trailer, running a steady 70 miles per hour on the four-hour Friday-night run to the lakeside cottage. This isn't just a Michigan thing: Manhattanites with second homes upstate, or Angelenos who like a weekend in Vegas now and then, raise your hands.

The centerpiece of GM's big-SUV-hybrid system is what GM engineers call a "two-mode" hybrid system. Boiling down some fairly complicated tech talk, the system works like this: Two electric motors housed inside the transmission, a 300-volt battery pack and some sophisticated software combine to supplement the energy from a 6.0-liter V-8 motor. >From a standing start, the hybrid SUVs can accelerate to about 20 miles per hour on electricity alone, if you depress the accelerator gently.

Click the above image for a diagram from General Motors showing how the two-mode hybrid system works.
When the big truck gets moving, the gasoline engine kicks in to get it up to highway speed. But once you settle into a fairly steady speed, four of the eight cylinders will shut down. A large SUV only needs about 30 horsepower to maintain its way at steady speeds, says Tim Grewe, chief engineer for the two-mode hybrid system. The hybrid system acts to expand the envelope within which the SUV can operate in four-cylinder mode, thus improving highway fuel economy.

"We use a battery to make a six-liter engine look like a three-liter," says Mr. Grewe.

The two-mode hybrid system constantly monitors the vehicle's performance, and juggles whether to run the engine on four or eight pistons, with or without electric boost. The electric-drive system regenerates juice in part by acting as the brakes and capturing energy as the vehicle decelerates. (Fully appreciating the hybrid Tahoe/Yukon will make you want to dust off your high-school physics lessons about mass, momentum and energy.)

During a brief drive around a GM test track, all this power management goes on almost undetectably. The transition from eight to four cylinders and back is seamless, as is the transition from strong electric boost to none. That can make you forget you are in a hybrid vehicle, which is one reason GM took a page from Toyota's marketing notebook and equipped the Tahoe/Yukon with hybrid badges and special displays to remind drivers (and neighbors) of the value received for the extra money spent on the hybrid technology.

For example, a navigation-screen display shows an animation of the power flows between engine and battery, and a simple gauge in the instrument cluster tells the driver when the vehicle is running at peak efficiency. While you shouldn't let playing the "Boost Your Mileage" videogame distract you from watching the road, the displays do encourage you to drive more sensibly.

What's notable about the hybrid Tahoe and Yukon, based on the explanations of GM engineers involved in the project, isn't just the "two-mode" electric-boost system. It's all the other things GM's engineers did to make the Tahoe and Yukon more efficient.

To reduce weight, the trucks will have aluminum hoods, tailgates, drive shafts and bumper structures. The body has been made more aerodynamic through "thousands of hours" of work in wind tunnels to fine-tune the placement of spoilers and air dams and so direct air around the body more efficiently. The seats have been slimmed down to cut weight, and the power-steering system is electronic, saving the weight of a hydraulic system.

The hybrid Yukon/Tahoe's body is about 400 pounds lighter than a standard model -- a significant reduction, but that's before you put in the hybrid drive, battery pack and related hybrid hardware. Once that's done, the weight's about the same, GM engineers say.

In many ways, the hybrid Tahoe and Yukon represent a response to the challenge posed to GM by environmental groups such as the Union of Concerned Scientists to sell vehicles that make use of fuel-saving ideas sitting on the shelf.

The bottom line for all of this effort, GM engineers say, is that the two-mode hybrid Tahoe and Yukon should consume about 25% less gasoline on average than a conventional, 5.3-liter V-8 two-wheel-drive Tahoe. That comes out to about 22.5 miles per gallon in combined city/highway mileage, based on the government's current mileage ratings.

But "your mileage may vary" are the key words. As owners of the Toyota Prius have reported, a lot depends on how you drive. Just because a car is a hybrid doesn't mean you can flog it through jack-rabbit starts and high-speed freeway jaunts and expect to achieve the EPA sticker mileage. You won't.

The two-mode hybrid Tahoe and Yukon, by themselves, won't change the energy equation for the U.S. Using the federal mileage estimates, you'd save about $453 worth of $3-a-gallon gas if you drove a hybrid Tahoe instead of a conventional 5.3-liter V-8 model.

Gary White, the GM vice president in charge of the auto maker's large-truck program, says GM is looking at other ways to boost large-SUV fuel efficiency, including diesel engines, which can cut petroleum consumption by about 25%. But marrying a diesel to the two-mode hybrid transmission/power management system might result in a truck that's quite expensive relative to its fuel savings.

GM plans to spread its two-mode hybrid technology to other models, including front-wheel-drive vehicles and smaller rear-wheel-drive vehicles. GM's partners in the two-mode hybrid development, DaimlerChrysler and BMW, will field vehicles of their own with the system.

GM hasn't disclosed the pricing for the hybrid SUVs, but GM executives hint that the prices will stay inside the current range for the models -- that is, somewhere between $35,000 and $45,000 or so.

A hybrid Tahoe will be one of a few hybrid vehicles on the market capable of carrying more than five people. GM says the Tahoe can be configured to seat eight people. (The Toyota Highlander hybrid has come in a seven seat configuration since 2005.) But a hybrid Tahoe might not be the most-efficient way to carry seven or eight passengers. Unless you have a trailer to tow, a conventional minivan would likely provide equivalent fuel economy at a lower price.

The question of whether the hybrid Tahoe will make a big difference in the broader context of the nation's energy debate comes down to economics and lifestyle. The nation's oil bill won't go down if solo commuters who dumped SUVs in favor of Camrys trade back to a hybrid Tahoe. But if the reception for the hybrid Tahoe and Yukon encourages GM to take more risks to push fuel-saving technology and designs into the market, that could mark a turning point.

New GM Hybrid coming soon..

ozpont