Hybrid Updates

Hybrid comments from Tech Show

By Sharon Terlep
Aug. 25, 2007

MILFORD – Dozens of General Motors Corp. engineers clad in look-alike polo shirts stood like an army at the ready Friday in the center of an intricate, science-fair-like display of model engine blocks and transmissions.

The technicians are GM's front line in a campaign to win a reputation as an auto industry technology leader – an image the company says it needs to survive in the brutally competitive U.S. auto market.

"We know that our success in the future is contingent on delivering technology that is meaningful to society," said Larry Nitz, executive director of GM's hybrid technology, who was among the team of engineers at GM's Milford Proving Grounds Friday to showcase the automaker's new powertrain technologies. "The whole spirit of the company is driven to do this."

GM thinks it can leverage its substantial research and development clout to change the American mindset that the automotive technology advantage goes to Japan. The automaker is hiring 400 specialized engineers to help with the mission.

A few years ago, those bragging rights were less coveted. But increasingly savvy consumers are looking for vehicles that not only boast speed, power and looks, but use less fuel and inflict less damage on the environment.

The Prius hybrid, in addition to being a sales success, was a public relations coup for Toyota Motor Corp., solidifying consumer perceptions that Toyota is years ahead of other automakers in the race for fuel efficiency.

It hasn't always been that way. Decades ago Detroit was known worldwide for driving automotive innovation, a reputation that waned amid cost cutting that led to fewer advancements and some major product blunders in the 1970s and '80s.

"As long as the vehicle was bigger, faster and had more bells and whistles, most Americans continued to buy those vehicles," says Philip Gott, director of automotive consulting for Global Insight. "The American (car makers) catered to where most of the people put their money. The Japanese looked at that and said, 'There's an opportunity to go the other way.' "

In the 1980s, Japanese automakers, particularly Toyota and Honda Motor Co., began a concerted effort to shed their image as copycats of successful U.S. and European innovations by taking the lead in developing new technologies, Gott said.

Detroit's Big Three, meanwhile, were less motivated to exert the same effort. Their vehicles already dominated the market, and they had suffered some product flops, including GM's loud and noisy diesel engines and a less-than-stellar attempt at an aluminum block engine.

"The traditional American buyer became very leery of new technology," Gott said.

GM, in particular, was stingy with research and development dollars, said Joseph Phillippi of AutoTrends Consulting in Short Hills, N.J. Instead of making new discoveries, GM fell back on technologies that were proven, if outdated.

"For decades, they've had tremendous technical resources in terms of engineering but it was grossly underutilized or underused or misapplied," Phillippi said. "Rather than invest in new technologies, they said 'Let's just " keep the old stuff because it's so profitable.'

Today, GM is working on 14 new powertrain programs for the 2008 model year, including the company's first attempt at a new type of gasoline engine it says can deliver more miles per gallon without requiring the emissions controls that drive up the cost of diesel engines.

The system, called a homogeneous charge compression ignition, would be 15 percent more fuel efficient by using the compression of fuel and air, rather than a spark, to produce the heat required to power the engine.

Other new powertrains are on the way, from the first gasoline-electric hybrid system for big trucks and sport utility vehicles to a wider array of engines capable of running on corn-based ethanol. The efforts are in addition to GM's widely publicized goal to have an electric plug-in hybrid, called the Volt, ready for the road by the end of the decade.

GM isn't alone in the technology push, with every major automaker pushing hard to develop fuel-saving options to win over mileage conscious drivers.

"We're all out there and we're all talking about what we're doing," said Ford spokesman Said Deep, who noted Ford's efforts to develop more hybrid engines, a fuel cell program and improvements on the internal combustion engine. "It's not just one automaker."

At GM, the giddiness is palpable among engineers who have moved from the relative anonymity of their laboratories to the center of GM's revival efforts.

GM powertrain chief Tim Stephens has been with GM nearly four decades. "There has never been anything close to the activity we have going on here."
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Note: I corrected the quoted title, as it stated 15 MPG improvement not 15% improvement.

Edmunds.com
Dan Pund Tech Report: GM's HCCI Engine Offers 15 MPG Increase
Date posted: 08-27-2007
DETROIT — While the Volt plug-in hybrid has made lots of headlines for General Motors, the company wants us to know that it's still busily refining gasoline and diesel engine technology.
Its latest effort is the HCCI internal combustion engine, a spark-ignition piston engine that can operate as a compression ignition motor, similar to a diesel. GM installed a version of the engine in both a Saturn Aura and an Opel Vectra and let us drive them around its proving grounds in Milford, Michigan.
General Motors says HCCI (Homogeneous Charge Compression Ignition) can yield a 15 percent improvement in fuel economy. But there are a few caveats. First, GM Powertrain Chief Tom Stephens says the technology won't likely reach production before 2015. And second, this impressive number includes the cumulative efficiency of variable valve timing and lift as well as direct injection, both of which must be in place for compression ignition to operate.
Compression ignition is all about the temperature inside the combustion chamber. In compression-ignition mode, the exhaust valves close earlier, trapping some of the heated air from the previous combustion cycle. This warms the incoming fuel mixture sufficiently to produce ignition once it's compressed by the piston. Clever stuff. But when the engine is under load — while accelerating, for example — the engine must transition back into spark mode to make full power.
This translates into a very narrow window of operation for compression ignition. Both light and heavy throttle applications sent the Ecotech four-cylinder into its default spark ignition mode. In fact, we were seldom able to keep the engine running on compression ignition mode. There's no mystery about the onset of compression ignition, as the engine starts knocking like an ancient diesel.
At this point, HCCI attracts far more attention from the driver than it should, and we're not yet persuaded that its effect will be greater than simple cylinder deactivation. Still, the gasoline engine clearly has a future, and we give General Motors credit for giving us a run in what is still a laboratory rat.
What this means to you: Mercedes-Benz is about to announce this technology at the 2007 Frankfurt Auto Show, so count this as one way in which the General is leading the way into the future.
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I believe this is part two fo the story:

After years of trial and error and secrecy, General Motors is ready to talk publicly about a combustion process that could increase fuel economy in conventional engines by up to 15 percent.

Uwe Grebe, executive director for GM's powertrain advanced engineering, told Thecarconnection.com that doesn't have a specific timetable for rolling out an engine with a homogeneous charge compression ignition, or HCCI, as the system is called. However, the fact GM has put experimental engines into a pair of demonstration vehicles suggests the technology could ready by the beginning of the next decade.

GM senior management is putting more and more emphasis on better fuel economy across its model line in an attempt to catch up with Asian rivals, which have long owned the franchise on fuel efficiency in the minds of most consumers.

The HCCI engine has several advantages that help make it more efficient, said Grebe. It doesn't need spark plugs inside the combustion chamber since the fuel is ignited by pressure, and it burns all the fuel inside the chamber completely, which eliminates the need for extensive pollution controls, Grebe said. The low-temperature, flameless energy release in the combustion chamber also means the engine uses less fuel, according to Grebe.

"Additional development costs, including research and testing programs, are required to make the technology ready for the great variety of driving conditions that customers experience,'' Grebe said.

When HCCI is combined with advanced technologies such as direct injection, electronic cam phasing, variable valve lift and cylinder pressure sensing, it can provides up to a 15-percent fuel savings, GM said. It is almost as efficient as a diesel engine but doesn't require the kind of extensive and expensive after-treatment of the exhaust necessary on diesel engines.

Richard Wagoner, GM chairman and chief executive officer, said recently the cost of diesel engine pollution equipment makes it very difficult to use small diesel engines in the U.S. where consumers don't have much of an inclination to pay extra for the technology.

GM's experts, like those at other automakers, have experimented with the technology behind HCCI engines for more than two decades. Only recently, however, have advances in computer software made it feasible to use the engines on production vehicles, Grebe said. The software helps smooth over the variability in combustion that occurs when the engine heats up or the atmosphere around the car changes.

Tom Stephens, group vice president GM Powertrain, said, while improvements in the standard internal combustion engines aren't very glamorous, they are cost-efficient. Standard gasoline engines are less expensive to build and offer excellent horsepower versus diesel engines.

Stephens said "there is no silver bullet" for improving fuel economy. GM, however, is committed to a broad strategy that will boost efficiency of engines and reduce emissions.

As part of the strategy, GM will introduce 14 new engines and transmissions for the 2008 model year, including eight that will be used exclusively in the North American market.

GM's two-mode hybrid system will debut on the full-size Chevrolet Tahoe and GMC Yukon on or about Nov. 1 and will be matched up with a new 6.0-liter V-8 engine, but will still get 25 percent more miles per gallon than a full-size SUV without the two-mode hybrid system.

"It will get better than 20 miles per gallon, even under the new EPA test," Stephens added. The EPA has made its test for calculating mileage tougher for the 2008 model year and the fuel-economy rating for many models, such as the Toyota Prius hybrid, are expected to drop.

The new hybrid system, which was refined at the hybrid development center operated jointly by GM, Chrysler and BMW in Troy, will be the first hybrid system used on full-size SUVs, which have become symbols of gas-guzzling in the ongoing controversy over fuel efficiency.

"The hybrid Tahoe is genuine SUV, only it's 25 percent better fuel economy," he said. The Chevrolet Tahoe and GMC Yukon hybrids will also deliver up to 40 percent better fuel-efficiency in city-driving, Stephens added.

Stephens also said GM plans to extend the use of the hybrid system to the Cadillac Escalade and crew cab versions of the Chevrolet Silverado and GMC Sierra during 2008.

Chrysler also is making plans to launch a hybrid version of its Dodge Durango, which uses the same basic system. The Chrysler system, however, has different formatting.

www.chicagotribune.com/business/chi-sat_gm_0825aug25,0,5908520.story
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Another article on the same engine

chicagotribune.com

GM building gas-sipping new engine

By Rick Popely

Tribune staff reporter

August 25, 2007

General Motors Corp. said Friday it is developing a gasoline engine that gets 15 percent better fuel economy than a conventional engine at lower cost than a diesel or hybrid.

GM's not saying when it expects to produce such an engine or what it will cost, but this is another indication the automaker is turning some serious attention to energy savings.

The engine technology, called homogeneous charge compression ignition, or HCCI, works somewhat like a diesel, using heat generated by compression instead of a spark plug to ignite the air-fuel mixture. It uses more air and less fuel than a conventional gas engine, reducing carbon-dioxide emissions and accounting for that 15 percent boost in fuel economy.

"I am confident that HCCI will one day have a place in our portfolio," Tom Stephens, GM's vice president of powertrain engineering, said at a press briefing in the Detroit area. GM demonstrated the technology with 2.2-liter 4-cylinder engines in two concept vehicles, midsize sedans. Daimler and Volkswagen also are exploring HCCI.

Diesels typically get 25 to 30 percent better fuel economy than gas engines. However, they cost around $2,000 more to produce and require additional exhaust equipment to catch soot and other pollutants. That adds thousands more.

GM said HCCI would cost less because it would use the same exhaust and emissions hardware as regular gas engines.

Besides, GM Vice Chairman Robert Lutz is not sold on the future of diesels.

Consumers are willing to pay $1,500 more for a diesel while the cost could be $5,000, he said, adding that U.S. emissions rules require so much exhaust plumbing "it looks like a Kentucky moonshine still."

"At this point, it's more hype than hardware," Lutz said of diesels.

Erich Merkle, an analyst at industry forecaster at IRN Inc., says few Americans outside of commercial users and truck owners who tow trailers are willing to pay that much more for a diesel. HCCI could appeal if it costs less and provides a tangible increase in economy, he said.

Diesels account for more than half of passenger car sales in Europe, where emissions rules are less stringent, because gas runs $6 to $7 a gallon with hefty taxes that have been in place for decades. Without that inducement, diesels don't sell in volume in the U.S. because "the cost is so great it just doesn't make sense," Merkle said.

The same goes for hybrids, whose batteries and electric motors add at least $2,000 to the price of a vehicle.

"With gas at $3 a gallon, it could take years to recover the extra cost of a hybrid," Merkle said.

And though just two weeks ago GM touted new lithium-ion batteries to power the Volt, slated to be in production by 2010, Lutz told a recent industry conference that it isn't clear what technology will emerge.

"We just don't know, so therefore we have to do everything," Lutz said.

Other automakers are taking similar approaches. Toyota and Honda, for example, are the leaders in hybrid sales but also are developing cleaner diesels and hydrogen fuel cells.

This scrambling to find the next big thing in fuel economy comes as Congress is debating proposals that would require vehicles to get as much as 35 miles per gallon by 2020, up from the current 27.5 m.p.g. for cars and 22.5 for trucks.

The industry will need a "potpourri of different technologies" to meet those standards, Merkle added.

Among other fuel-saving measures they are tapping are direct fuel injection for gas engines, cylinder deactivation, 6- and 7-speed automatic transmissions and weight reduction.

"None of those is free," he pointed out. "If fact, they're very expensive. At $3 a gallon, fuel economy is still not a big priority with consumers, so there is the question of whether they will be willing to pay for it."

[email protected]

GM engine may save fuel

Technology could cut consumption 15%
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Fourth Article

GM engine may save fuel
Technology could cut consumption 15%
August 24, 2007
BY KATIE MERX and MARK PHELAN
FREE PRESS BUSINESS WRITERS
Today General Motors Corp. executives will show off a new engine technology that could cut fuel consumption by up to 15%.
The savings are the product of an engine-transmission system known as homogeneous charge compression ignition, or HCCI, that marries the high fuel economy of a diesel engine with the relatively low emissions of gasoline engines.
With the potential to deliver better fuel efficiency than even some of its gas-electric hybrids, GM calls HCCI "the most awaited advanced combustion technology of the past 30 years." Mercedes-Benz soon will show its own version of the technology, though neither automaker has said when it will make them in production vehicles.
"By combining HCCI with other advanced gasoline engine and control technologies, we can deliver a good fuel savings value for consumers," Tom Stephens, group vice president for GM Powertrain and Quality, said in a statement. "It is another initiative in GM's advanced propulsion technology strategy to lessen our dependence on oil. ... I am confident that HCCI will one day have a place within our portfolio of future fuel-saving technologies."
GM is expected to demonstrate the HCCI combustion process today using two driveable concept vehicles, a 2007 Saturn Aura and a 2007 Open Vectra. Both vehicles are powered by modified 2.2-liter Ecotec four-cylinder engines. GM says the engines can generate 180 horsepower.
GM declined to say what fuel-efficiency figures the HCCI Saturn Aura might achieve in the Environmental Protection Agency tests that produce the window-sticker fuel economy figures automakers advertise.
However, a 15% improvement over an Opel Vectra currently on sale in Europe works out to be about 26 m.p.g. in the city, 43 m.p.g. on the highway and 35 m.p.g. in mixed use on the European Union's standard fuel economy test. That test is different from the EPA's procedure, but it suggests the HCCI engine would surpass the fuel economy of GM's 2008 Saturn Aura gasoline-electric hybrid.
"This truly is something different," said auto analyst Erich Merkle of IRN Inc.
David Cole, chairman of the Center for Automotive Research, agreed that it is a big deal.
"It's the kind of thing that will have a significant competitive dimension to it," Cole said.
GM's HCCI engine is among the first in a flood of high-efficiency powerplants automakers are developing to combine the high fuel economy of a diesel with the low emissions gasoline engines produce.
Mercedes-Benz plans to show an experimental engine that adds three more technologies to the concept for even higher fuel economy at the Frankfurt auto show in Germany next month.
Mercedes has not allowed journalists to test-drive any vehicle with its proposed engine yet, and will not say when it hopes to have the engine in production.
Mercedes' concept engine uses a turbocharger, an electric hybrid system and a variable compression ratio in a 1.8-liter four-cylinder engine. Mercedes calls the concept DiesOtto, a combination of the German names for diesel and gasoline engines. Mercedes says its engine could generate 238 horsepower and achieve 30 m.p.g. in a Mercedes S-class luxury sedan on the European test cycle that combines city and highway driving.
As automakers compete to be first to market with an HCCI engine, however, they continue to work on many other technologies as well, and GM is expected to introduce the 14 new or significantly revised powertrains it will make available in the 2008 model year.
Among the powertrains GM is expected to highlight today:
• The new two-mode hybrid system that will be available this year with a new 6.0-liter, V8 in GM's full-size SUVs. GM says the two-mode hybrid system delivers 332 horsepower and towing-friendly torque.
• Hybrid versions of its Saturn Vue, Saturn Aura and Chevrolet Malibu.
• Five new 1.0-liter and 2.0-liter engines for Europe, Asia and Latin America
• A new 3.6-liter V6 with direct injection for the Cadillac STS and CTS luxury sedans.
• Nine new six-speed transmissions that the automaker says will provide up to a 4% improvement in fuel savings and a 7% improvement in performance.
"For the most part, GM has a leg up on its competition in terms of fuel efficiency; they just get little credit for it," Merkle said. "They've really done some impressive things with fuel efficiency and performance."
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More info

GM tests technology that could raise fuel economy by 15 percent
August 24, 2007

By TOM KRISHER
AP Auto Writer

DETROIT (AP) -- General Motors Corp. says it is testing a combustion process in concept cars that could raise fuel economy by 15 percent over current conventional engines.

The announcement comes as fuel economy has become an increasingly important issue as gasoline prices have risen. Foreign automakers have captured a bigger share of the U.S. market in part by emphasizing fuel efficiency.

The process GM and other automakers are testing, called homogeneous charge compression ignition, approaches the fuel efficiency of a diesel engine without the need for advanced pollution controls, GM said in a statement.

It is being tested in two drivable concept vehicles, a Saturn Aura and an Opel Vectra, and was shown to reporters Friday at GM's proving ground in Milford.

The process ignites an air-fuel mixture in the cylinders by compressing it, producing a low-temperature, flameless energy release in the combustion chamber, the company said. Since all the fuel in the combustion chamber is burned more quickly than conventional spark-ignition engines, the engine uses less fuel to produce power that is similar to conventional engines.

GM estimates the technology is six or seven years away from showrooms, mainly because it still needs to work on controlling the combustion process.

"Additional development costs, including research and testing programs, are required to make the technology ready for the great variety of driving conditions that customers experience," Uwe Grebe, executive director for GM's powertrain advanced engineering, said in a statement.

With the working concept cars, GM appears to have taken the lead on the technology over a number of other companies that are testing it, said John Dec, a distinguished member of the technical staff at the U.S. Department of Energy's Sandia National Laboratories in Livermore, Calif.

The technology holds great potential to make engines more efficient and pollute less since its combustion takes place at lower temperatures without the waste products of higher-temperature ignition, Dec said.

"The engine-out emissions in a true HCCI engine are so low that you could meet current and future emission regulations without after-treatment," said Tom Ryan, an engineer at the Southwest Research Institute in San Antonio who has studied the technology.

The technology could be more efficient than diesel engines with less pollution, said Ryan, the incoming president of the Society of Automotive Engineers.

GM is running its prototype cars with the new technology during intermediate loads on the engine, but must revert to a spark ignition at higher loads, Dec said.

"That transition is a little bit tricky, but they've worked it out well enough to make these cars work," said Dec, who also has done research on the compression system.

If a company can run an engine over the entire range of driving conditions, it will achieve even greater efficiency, Dec said.

"Theoretically in the lab we can go like 30 percent," he said. "The problem is you have to make that work over the whole driving cycle."

The technology has been studied for years, Dec said, but research has accelerated since about 2000.

GM shares rose 30 cents to $31.05 Friday.

---

On the Net:

http://www.gm.com
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More

AutoWeek | Updated: 08/27/07, 11:40 am et

The star of General MotorsÂ’ Powertrain Technology Show is homogeneous charge compression ignition (HCCI). It took 30 years to make this engine a reality. The idea of this engine hasnÂ’t been very secret. Tinkers and high-quality teams have tried to perfect it, but the GM team led by Uwe Grebe, executive director for GM Powertrain Advanced Engineering, has succeeded.

“I remember debating the limits of combustion capability when I was in college,” said Tom Stephens, group vice president, GM Powertrain and Quality. “HCCI was just a dream then. Today, using math-based predictive analysis and other tools, we are beginning to see how we can make this technology real. By combining HCCI with other advanced gasoline engine and control technologies, we can deliver a good fuel-savings value for consumers.”

GM says, “An HCCI engine ignites a mixture of fuel and air by compressing it in the cylinder. Unlike a spark-ignition gas engine or diesel engine, HCCI produces a low-temperature, flameless release of energy throughout the entire combustion chamber. All of the fuel in the chamber is burned simultaneously. This produces power similar to today’s conventional gas engines, but uses less fuel to do it. Heat is a necessary enabler for the HCCI process, so a traditional spark ignition is used when the engine is started cold to generate heat within the cylinders and quickly heat up the exhaust catalyst and enable.”

We drove one of the two concept vehicles with the HCCI engine at the companyÂ’s proving ground. It seemed like a regular car, which we drove to 70 mph. In idling, however, the engine didnÂ’t sound a growl. GM says HCCI provides up to a 15 percent fuel savings and meets current emissions standards. GM didnÂ’t say when the HCCI would appear in vehicles for sale.

GM revealed that it will launch 14 new or revised powertrains for 2008, including five 1.0-liter to 2.0-liter small-displacement engine variants, seeking to save fuel and improve performance in GM cars and trucks. That powertrain includes hybrids, clean diesels and fuel-saving technologies such as direct injection, six-speed transmissions, renewable biofuels and small-displacement engines for Asia, Europe and Latin America.
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Few quotes from the biggest news outlets.

"A few hours in a preproduction Tahoe hybrid around Northern Virginia, in traffic and on highways, was satisfying. Tahoe was smooth as you please in stop-go because the electric motor, which handles low-speed driving, provides all its power the instant it begins to turn. - Jim Healey, USA Today

"It all worked flawlessly. When I'd slow down for a light, the vehicle's regenerative brakes would gather energy and the gas engine would shut down. When that light turned from red to green on 19th Avenue, I slowly depressed the pedal and cruised along in electric mode until I reached about 30 mph. Then the gas motor kicked in." - Matt Nauman, San Jose Mercury News


"After checking out GM’s new entry to the green car market, I was surprised — practically amazed — and convinced the new hybrid design could be a game changer. The engineering advancements that GM was showing off in the Yukon hybrid GM brought to Manhattan on a recent morning were impressive in their own right.. Likewise, the scope of GM’s vision to roll out the new system into new models left me more convinced of the company’s commitment to a technology it was dismissive of a few years back. - Adam Aston, Businessweek.com

Also, have attached a collection of articles.
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Details:

Going hybrid makes Tahoe a treat
Better mileage a given: What's surprising? Better everything else
By James R. Healey
General Motors plans to start selling gasoline-electric hybrid versions of its full-size Chevrolet Tahoe and GMC Yukon SUVs this fall, hoping their improved fuel economy will attract mileage-minded buyers back to the potentially profitable big SUV market.
The hybrids will come only well-equipped. But GM says they won't be the most expensive in the $35,000-to-$55,000 Tahoe/Yukon line.
A few hours in a preproduction Tahoe hybrid around Northern Virginia, in traffic and on highways, was satisfying.
Tahoe was smooth as you please in stop-go because the electric motor, which handles low-speed driving, provides all its power the instant it begins to turn. Gasoline engines have to rev a bit. GM says the electric-only mode could take you to 32 mph under ideal conditions. But the test showed that accelerating in traffic means electric-only lasts only up to about 10 mph.
The hybrid tows less, 6,000 to 6,200 pounds vs. 7,500 to 8,200 on gasoline models. No tow test was scheduled, but a stop at the Hobby Hangar in Chantilly, Va., a store that sells remote-control cars, planes and boats, provided an opportunity. The folks there, beyond all reason and good sense, offered the store's trailer. It was empty and probably weighed 1,000 pounds, according to the consensus, but it at least hinted how the hybrid would tug.
Very well, it turns out, with the trailer behind and five guys aboard the Tahoe.
Towing or otherwise, under hard throttle the hybrid was quieter than normal Tahoes and felt as if it weren't gaining speed fast. But it was. About the time your rump said 50 mph, the speedometer showed 70. What seemed 35 or 40 mph was 50 mph or faster.
Typical of hybrids, Tahoe saves fuel by shutting off its gasoline engine at stoplights and when the electric motor is sufficient to power the truck. But also unfortunately typical, Tahoe's gasoline engine shuddered as it fired up and began contributing power. Expect the shakes to be gone in regular production models, says Mark Cieslak, chief engineer for GM's full-size trucks.
The transmission got hung up on full-throttle shifts, holding the engine at 5,500 rpm too long, followed by a falloff in power, before up-shifting. Also gone by production, Cieslak promises.
The test truck's trip computer showed about 18 miles per gallon, less than the 20 or so GM forecasts, but the few miles of light towing hurt a lot.
The hybrid number beats the 13-to-17 real-world mpg of a gasoline Tahoe (Test Drive, January 2006).
GM predicts 40% better mileage than the gasoline model in city driving, where most people spend time.
Hybrids qualify for income-tax credit. That hasn't been calculated or approved by the government yet.
Converting to a combination of gasoline and electric power to improve fuel economy has improved the vehicle overall. Here's how:
•Lighter components wash out some 300 pounds of the 400-pound weight penalty imposed by the hybrid system's two electric motors, big battery pack and associated bits. Thus, the Tahoe hybrid hood and tailgate are lightweight aluminum and easier to lift and lower than the steel items on non-hybrid trucks.
Reconfigured front seats not only weigh less, they open 1.6 inches (40 millimeters, to be precise) more legroom for second-row riders.
The hybrid's 6-liter V-8 is aluminum alloy instead of the heavier, iron 5.3-liter V-8s in gasoline-only Tahoes, lessening front-end weight and providing better-balanced handling. Still not what you call sporty, as a fast run down an offramp will demonstrate.
The 6-liter has nearly 4% more horsepower and 8% more torque than the 5.3-liter in gasoline-only Tahoes.
•Reshaping front and rear panels improves airflow for better highway mileage. The subtle changes, plus lowering the vehicle 0.4 of an inch (10 mm), which also helps airflow, make the handsome Tahoe look even better. Tucking and trimming and better-integrating the running boards for airflow improvements dramatically boost the eye appeal of the rocker-panel area. Even aesthetically enlightened souls who hate running boards will find it hard to complain.
•Small details get attention. Switching from conventional taillights to light-emitting diodes (LED) adds — GM swears — 0.1 to 0.2 miles per gallon, because LED take less energy to illuminate. And they look cool.
•Serendipitous synergies are unlocked. Regenerative braking (regen), part of any hybrid, delivers firmer-feeling brakes the truck has needed. It turns the motor into a generator as you slow the vehicle, pumping juice back into the battery pack. That way, the gasoline engine doesn't have to come on as soon, as often, just to recharge the batteries. GM credits regen for 40% of the hybrids' total fuel economy improvement.
Electric power steering avoids the fuel-using engine drag of conventional, belt-driven power steering and improves the truck's steering feel.
Redesigning the front seats all but eliminated the overdone lumbar bulge that ruins many GM seats.
The automaker says it might eventually use some of the weight-saving measures on non-hybrid models.
If the preproduction tester is a true harbinger, and if hybrid prices aren't absurdly high, then GM is doing a great favor to buyers who need the beef and brawn of a truck-style SUV but have been scared off by poor mileage and high fuel prices.
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[FONT=&quot]Test Drive: GMC [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot] Hybrid[/FONT]
[FONT=&quot]BETTER FUEL ECONOMY, SEATS FOR 8 AND TOW POWER[/FONT]
[FONT=&quot]San Jose[/FONT][FONT=&quot] Mercury News[/FONT]
[FONT=&quot]Matt Nauman[/FONT]
[FONT=&quot]8/24/2007[/FONT]
[FONT=&quot]General Motors' first full hybrid reaches showrooms in November, and now that I've driven one, I can testify that it arrives as promised. Sold as either a Chevrolet Tahoe Hybrid or a GMC Yukon Hybrid, it's a full-size sport-utility with as many as eight seats and the capability to tow a boat that also delivers a fuel-economy gain and can even run on pure electricity. [/FONT]
[FONT=&quot]Micky Bly, GM's director of hybrid powertrain integration, rode with me as I drove a prototype version of a [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot] 2-mode hybrid on highways and crowded city streets in [/FONT][FONT=&quot]San Francisco[/FONT][FONT=&quot] last week. He says the vehicle will get 25 percent better fuel economy overall than the gasoline-only version, and about 40 percent better in city driving. [/FONT]
[FONT=&quot]That's about five or six more mpg in the city and one to two more on the highway, he says. [/FONT]
[FONT=&quot]The 2008 2WD GMC Yukon with a 5.3-liter V-8 gets 14 mpg in the city and 20 mpg on the highway, according to the government's [/FONT][FONT=&quot]www.fueleconomy.gov[/FONT][FONT=&quot] Web site. Using Bly's numbers, that means the hybrid (which uses a 6.0-liter V-8 for better low-end torque) ought to get 19 to 20 mpg in the city and 21 or 22 mpg on the highway. The vehicle is undergoing certification right now, he says. [/FONT]
[FONT=&quot]The target customer? "It's clearly going to be the customer who needs an SUV's five-, six-, seven-, eight-passenger capability. They tow their boats. They go camping. They really have a need for this SUV," Bly says. "But they also want to [/FONT]
[FONT=&quot]make sure they're ecology-conscious, that it's important to get the best fuel economy." [/FONT]
[FONT=&quot]On my short drive, it was obvious that Bly and his peers - about 250 engineers from GM, Chrysler and BMW who have partnered to create this 2-mode hybrid system, in Troy, Mich. - have achieved a nice balance. [/FONT]
[FONT=&quot]If anything, the driving experience of the GMC Yukon 2-mode hybrid was even more seamless than in other hybrids I've driven. It's all pretty complex, considering that the vehicle also includes GM's Active Fuel Management (AFM) system that cuts out half of the V-8's cylinders when they're not needed. [/FONT]
[FONT=&quot]So, the engine moves from V-8 to V-4, and switches to electric power, too. [/FONT]
[FONT=&quot]It all worked flawlessly. When I'd slow down for a light, the vehicle's regenerative brakes would gather energy and the gas engine would shut down. When that light turned from red to green on [/FONT][FONT=&quot]19th Avenue[/FONT][FONT=&quot], I slowly depressed the pedal and cruised along in electric mode until I reached about 30 mph. Then the gas motor kicked in. [/FONT]
[FONT=&quot]While this [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot] hybrid closely resembles the gasoline version, there are significant changes. [/FONT]
[FONT=&quot]The hybrid components, including the 300-volt nickel-metal hydride battery pack, add about 400 pounds to the truck's weight. Engineers took out 320 of that by making lighter seats, making the hood and rear hatch out of aluminum and removing some unneeded bits such as the starter motor and alternator. [/FONT]
[FONT=&quot]Designers made the vehicle more aerodynamic, with a new front end, a rear spoiler and even new wheels and running boards that lessen wind resistance. [/FONT]
[FONT=&quot]The battery pack is under the second seat, so passenger and cargo room remains the same. [/FONT]
[FONT=&quot]The 2-mode hybrid transmission - "a piece of art," Bly says - fits into the same space as a standard six-speed automatic. It contains two 60-kilowatt motors, and has four fixed gears, three planetary gear sets and four clutches. [/FONT]
[FONT=&quot]It, plus regenerative braking, allows improvements in both city and highway driving, thus the 2-mode designation. In the first mode, either electricity, the gas engine or both operate. In the second mode, at highway speeds, the electric bits boost the gasoline V-8. [/FONT]
[FONT=&quot]Prices haven't been announced, but expect the hybrid versions of the Chevy Tahoe and GMC Yukon to be similar to those of its top-line gasoline trim levels. For Chevy, that's the Tahoe LTZ at $45,680. For GMC, that's somewhere between the $39,890 Yukon SLT and the $49,910 Yukon Denali. [/FONT]
[FONT=&quot]"This will not be the most expensive [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot] you can buy," said GMC spokeswoman Monique Brentley. [/FONT]
[FONT=&quot]GM won't discuss sales forecasts either, although Bly said manufacturing capacity, including the supply of batteries, won't be a problem. [/FONT]
[FONT=&quot]I've probably talked to a dozen GM execs over the past five years, listening as they detailed their hybrid strategy. [/FONT]
[FONT=&quot]It starts with buses, they say, as that's a great way to improve fuel economy with big people movers. Then it evolved into mild hybrids, vehicles including big trucks, sport-utilities and a few cars that can get a small mpg boost (for a relatively small cost) by adding a bit of hybrid technology. [/FONT]
[FONT=&quot]And, finally, now, comes GM's 2-mode hybrid technology. [/FONT]
[FONT=&quot]We're not behind [/FONT][FONT=&quot]Toyota[/FONT][FONT=&quot], those GM officials insisted. We just have a different strategy. [/FONT]
[FONT=&quot]The problem was that Honda first sold a hybrid in the States in 1999, and [/FONT][FONT=&quot]Toyota[/FONT][FONT=&quot] brought out the Prius in 2000. [/FONT][FONT=&quot]Toyota[/FONT][FONT=&quot] has grabbed the reputation as the king of hybrids, led by its bestselling Prius, but also including two other Toyotas and three Lexus models. Most buyers are just now becoming aware that GM has entered the hybrid game. [/FONT]

[FONT=&quot]It'll be interesting to see how that perception evolves. So far, unique models such as the Prius and smaller ones such as the Honda Civic have proven most popular. Bringing out hybrid SUVs at a time when SUV sales are falling, but admittedly mostly due to higher gas prices, represents a marketing challenge.[/FONT]
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More:

The Devil Drives a Chevy Tahoe Hybrid
Wednesday, August 15, 2007
GM's new hybrid face

Temptation.

That's the best way to describe my Chevy Tahoe hybrid test drive yesterday. Pure and simple temptation.

I mean large, gas-guzzling SUVs are destroying the world, right? Besides, when I was invited to test drive one of GM's first dual mode hybrid vehicles, I did it to test the technology, not to see if I liked the vehicle. I hate these SUVs, right?

So, why am I again tempted?

Back at the Detroit Auto Show, I was given a ride from the show back to the airport in an Escalade. It was a damn nice ride that made me feel guilty for realizing that it was a damn nice ride, and I remembered this realization as soon as I sat in the hybrid Tahoe's big, luxuriously comfortable seats.

Again, I am tempted.

Maybe it's my six foot frame, or my bad lower back. Maybe, deep inside the recesses of my soul, I have SUV envy. Maybe it's my Midwestern influence and the memory of driving through the snow, sleet and hail. Maybe I just feel safe and very comfortable inside such vehicles as the Tahoe hybrid.

Regardless, these vehicles tempt me, especially hybrid versions of these vehicles because I believe in hybrid technology. Hybrid technology in any passenger vehicle helps drive down the costs of hybrid technology for all passenger vehicles, especially the small hybrid cars that I prefer to buy.

True, some automakers are using hybrid technology to simply add more power to a vehicle, and using hybrid technology purely for performance gains is a slippery path. Fortunately, the Tahoe hybrid is not one of those hybrids.

While the standard Tahoe achieves a paltry 14 mpg in the city - where I do 95 percent of my driving - the Tahoe hybrid achieves 20 mpg. This 40 percent improvement in fuel economy is achieved as the Tahoe intelligently utilizes its dual mode hybrid powertrain, deciding how many cylinders to use, how much regenerative electricity, etc. For example, the Tahoe hybrid can go from V8 power to acting like a V4 economy vehicle, instantly, without the driver ever noticing, and that's just one trick in the dual mode hybrid's bag of tricks.

Still, while driving through the streets of Santa Monica, I didn't notice this shift, or any other of the vehicle's hybrid shifts and tricks, except when I was watching the hybrid screen on the dashboard display how the hybrid powertrain was being utilized.

Speaking of hybrid screens. GM has done a nice job of supplementing the somewhat conventional hybrid screen with a small gauge next to the speedometer. This gauge helps drivers simply maximize the performance of GM hybrids, to fully utilize the hybrid's bag of tricks to hypermile through commutes - if they so choose.

But, back to the transmission shifts, or lack thereof, caused by the hybrid powertrain. Instead of such shifts, what I was able to notice was quick acceleration, responsive handling and a smooth ride. What Tahoe fans will realize, however, especially city-folk, is the huge savings at the gas pump - the main distinction between the standard Tahoe and the hybrid Tahoe ( Yes the Tahoe hybrid also offers some unique badges, running boards, grill, rims, etc, as well.).

And, while 20 mpg is an amazing improvement in efficiency, what makes it even more amazing is the fact that you can connect a 6,000 pound camper, boat or other trailer to the hybrid Tahoe, and drive out of the city up into the mountains for a weekend getaway and not lose any performance.

What other hybrid can do that?

Answer, there isn't one, other than the Tahoe hybrid's cousin, the GMC Yukon hybrid. In this respect, GM's hybrid vehicles are in a class of their own, and now there is no excuse for weekend warriors hauling campers and boats across the highways of America not to do more to help the environment and to help reduce America's foreign oil dependency.

While GM couldn't confirm the price of the Tahoe hybrid, I was told that the hybrid version would not be the most expensive Tahoe option. Still, it will be mostly loaded and it will have a price tag to match that luxury, in addition to the hybrid-driven fuel economy.

Nonetheless, both the Tahoe and the Yukon hybrids give large SUV fans, especially GM fans and American-made automobile fans, a chance to take some foreign oil dependency responsibility.

If you have to have a large SUV, make sure to check out the Tahoe and Yukon hybrids when they come out later this year. Be tempted into making a better decision, it's really not that hard if you just drive one of these hybrids. Even a SUV-hater like me was tempted.
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More

[FONT=&quot]August 20, 2007[/FONT]
[FONT=&quot]Hybrids, Heels and Wheels[/FONT]
[FONT=&quot]Jody DeVere[/FONT]
[FONT=&quot]Askpatty.com[/FONT]
The 2008 Tahoe Hybrid is coming in the fall of 2007 utilizing GM's 2-Mode Hybrid system, a technology that GM hopes will take the lead into the world of competitive hybrid vehicles. I had the opportunity to test drive this new 2008 vehicle which will be built in Arlington, Texas.
I took a walk around the Tahoe Hybrid before my test drive and found the rear hatch to be a soft electronic latch which saves on nail breakage. The running boards are retractable and standard equipment and good for hopping up or out in high heels. Kids and smaller adults will appreciate the running boards as well. The wheel base is slightly lower too.
The test drive vehicle had large HYBRID signs on it and I giggled as I started it up looking forward to the spectacle of cruising around in busy Santa Monica traffic being so BIG and SO Green.
The design of this car was influenced by the clever GM Vehicle Line Director Mary Sipes, a 25 year GM veteran with many great stories to tell.
Recent Article Excerpt:
Mary Sipes, one of several women who have made it into the upper echelon of GM management, is the mastermind behind one very unusual day.
Ms. Sipes' MBA and her on-a-mission determination to produce the best vehicle for the customer has put her near the very top of a very male business. Engineers, designers, purchasers and all involved in GM's future, full-line SUVs work with her. Sipes answers to Gary White, GM North America Vice President and Full-Size Truck Vehicle Line Executive, who is in charge of the new 900-platform, which includes the Tahoe, Suburban, Denali, Escalade and Avalanche.

When the SUVs were in development, Ms. Sipes took the future, full-line SUV team out to the proving grounds to do some vehicle testing. They expected the usual driving exercises, but she had another idea. Hint, hint: On the way she stopped at a shoe store to buy several pairs of size-12 high heels.

"A few times a year we go off site and try to have a learning exercise that is a lot of fun," said Sipes. "We took our group to the proving grounds and broke them into teams. One guy on each team had to be Mr. Mom. We dressed him in a garbage bag to simulate a tight skirt. We gave him rubber gloves with press on nails, a purse, a baby and a baby stroller and some chores like loading groceries."

With all female handicaps in place, the men were then required to go through what women do routinely every day. They had to put the baby in a car seat and buckle them in, fold up the stroller, pull up the liftgate and stow the stroller, put grocery bags in the back. They then had to walk around the vehicle and step into it not using the running board. Wearing the gloves with press on nails they had to operate the key fob, adjust the radio and then figure out what to do with their purses-without breaking or losing a nail. Lost or broken fingernails or torn garbage bag skirts resulted in points against the final score.

"We had a lot of laughs," said Sipes, "but the men's awareness of how women function in the vehicle really changed."
--------
I met the GM Mr. Mom mentioned here, ( Mark Cieslak, Chief Engineer for GM Hybrid Trucks), and I can assure you GM is passionate about their products and this Chevy SUV GM group understands the needs of women car buyers.
Bonus: There is even a large center compartment to store your purse! Thank you Mary Sipes and the GM design team, every woman I know complains about not having this feature.
In electric mode the Tahoe Hybrid is very quiet drive with lots of dash and LCD controls to help keep in maximum fuel economy mode are nice and easy to read and understand. Mash the gas and you will find it to be very responsive. Power is there when you need it.
Designed to meet the highest safety standards, this Hybrid SUV comes with sensors to shut down battery power if crash is detected. General Motors has not finalized standard safety equipment or interior options for the Tahoe, which is expected to go on sale later in 2007 however, Mark Cieslak, Chief Engineer for GM Hybrid Trucks assured me there will be "no compromise" on safety for this vehicle.
All GM models come with the OnStar basic package for one year. For more about OnStar go here.
Best feature? The 2008 Chevy Tahoe Hybrid gets 25% less consumption of fuel over a long term and 40% improvement in city driving.
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...

Green Biz

A green Cadillac? GM's surprising new hybrid

Posted by: Adam Aston on August 16
businessweek.com
After checking out GM’s new entry to the green car market, I was surprised — practically amazed — and convinced the new hybrid design could be a game changer. The engineering advancements that GM was showing off in the Yukon hybrid GM brought to Manhattan on a recent morning were impressive in their own right — more on that later. Likewise, the scope of GM’s vision to roll out the new system into new models left me more convinced of the company’s commitment to a technology it was dismissive of a few years back. Indeed, GM has been talking about this new so-called “2-mode hybrid” for years. Whether GM could scale it up into full production was a big question, though. The proof sat parked in the guise of an aerodynamically sculpted SUV (that sounds like an oxymoron, I know, but is true) parked outside a restaurant in New York’s art gallery district. It goes on sale later this year.
The new hybrid design is a smart blend, joining a smart, new organization of the gas-electric drive train with GM's existing engine technology that imperceptibly turns off cylinders at cruising speeds. The combination improves mileage in city traffic and also while cruising on highways. GM pledges this approach will deliver a 20-25% mileage boost overall, even on big SUVs and pickups, and without sacrificing the horsepower American car buyers crave. Given GM's offerings in the hybrid market to date -- so-called mild hybrids like the Chevy Silverado with unimpressive mileage gains -- the new technology is a giant leap forward.
First the technical details. If you could dismantle a Toyota or Ford hybrid today, you'd find a chunky electric motor connected up to the motor and drive train. Yet if you disassemble a Yukon, you won't see any electric motor. That's because GM was able to sneak a powerful electric generator into the big case that holds the transmission gears. This has many benefits. It saves space, since the transmission case is no bigger, even with the extra electric bits. The design should also make it easier for GM to adapt hybrid drive trains into other cars. And there may energy efficiency advantages in this approach (compared with the Toyota, Honda, Ford design) because it cuts down on the number and complexity of mechanical linkages necessary to join electric motor to gas engine. (Any mechanical engineers out there want to weigh in?). As an added plus, it frees up precious underbody space for batteries, regenerative braking systems, and the other goodies that make hybrids go.
On a cruise north up 10th Avenue, to Manhattan's northern reaches, though about as un-nimble as any big SUV in city traffic, the Yukon was quiet and smoother than its gas-only cousin. This, explained Mark Cieslak, vehicle chief engineer of GM's full size truck hybrids who's been driving an early production hybrid Yukon for months, is because the battery pack and electric motor have enough kick to take this 5,000-lb vehicle up to city road speeds without the 6 liter V-8 gas engine kicking in. Once at highway speeds, driving south along the Hudson River, the engine saves gas by deactivates cylinders not needed to maintain a 65-mph clip.
Back to the big view. In debuting the Yukon, GM representatives also walked a group of reporters through their hybrid strategy plan for years to come. Earlier, I blogged about my skepticism that GM could beat Toyota to a plug-in electric hybrid. But step by step they outlined makes me think they could do it. The hybrid GMC Yukon, and its doppleganger the hybrid Chevy Tahoe, will hit sales lots late this year. Soon there after, the 2-mode hybrid will appear in 2008 models, including a hybrid Cadillac Escalade -- what better way to assuage SUV guilt? -- followed by 2-mode hybrid treatments of the Chevy Silerado/ GMC Sierra pickup, and a similar upgrade to the Saturn Vue Green Line all in 2008. Sure enough, at the end of this road map, in 2009/2010, GM shows two plug-in hybrids: the Saturn Vue Green Line and the Chevrolet Volt.
Oddly, GM won't be deploying this 2-mode system into any sedans, just SUVs and trucks. Given GM's success (at least till $3 gas) with trucks and SUVs, this makes sense: Americans don't necessarily want sedans, they're justing more of them now since they get better mileage. If you can deliver a small SUV with car like mileage, who wouldn't opt for the bigger vehicle? This omission may be because the new all-in-one transmission-plus-electric-motor is too bulky to fit into smaller car forms.
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The 2-Mode is a nice approach in my opinion. It allows for gear lock up and not only electric motors so when one is at freeway speeds the motros do not have to spin even when they are not prodcing any energy to the wheels. They still would be spinning mass. The 2 mode allos for the motors to not spin when the IC engine would be engaged.


[FONT=&quot]GM's 2-Mode 2008 [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot] Hybrid[/FONT]
[FONT=&quot]Kevin Massy[/FONT]
[FONT=&quot]CNET Reviews[/FONT]
[FONT=&quot]Full hybrids have to date been almost synonymous with [/FONT][FONT=&quot]Toyota[/FONT][FONT=&quot]'s Hybrid Synergy Drive (HSD) system, which, in addition to being the technology behind all [/FONT][FONT=&quot]Toyota[/FONT][FONT=&quot] and Lexus hybrids, is licensed by Nissan for its [/FONT][FONT=&quot]Altima Hybrid[/FONT][FONT=&quot] and is used in a modified version by Ford in the [/FONT][FONT=&quot]Ford Escape[/FONT][FONT=&quot] and [/FONT][FONT=&quot]Mercury Mariner [/FONT][FONT=&quot]hybrids. This hybrid monopoly is about to change, however, as GM readies its 2-Mode hybrid system for introduction later this year in the Yukon Hybrid and Tahoe Hybrid SUVs. Like HSD, GM's 2-Mode system enables cars to run just on electricity, just on gasoline, or a mixture of the two. The system makes use of a two electrically controlled variable transmission (ECVT) modes, which change based on the car's speed and engine demand. The result, according to GM, is a 40 percent improvement in city fuel economy over the gasoline-only [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot], and a 25 percent improvement in overall gas mileage. [/FONT]
[FONT=&quot]We took a ride along with GM this week in the 2008 Yukon Hybrid and got a first-hand impression of the next big thing in the hybrid world.

GM's 2-Mode 2008 Yukon Hybrid
Kevin Massy
CNET Reviews
Full hybrids have to date been almost synonymous with Toyota's Hybrid Synergy Drive (HSD) system, which, in addition to being the technology behind all Toyota and Lexus hybrids, is licensed by Nissan for its Altima Hybrid and is used in a modified version by Ford in the Ford Escape and Mercury Mariner hybrids. This hybrid monopoly is about to change, however, as GM readies its 2-Mode hybrid system for introduction later this year in the Yukon Hybrid and Tahoe Hybrid SUVs. Like HSD, GM's 2-Mode system enables cars to run just on electricity, just on gasoline, or a mixture of the two. The system makes use of a two electrically controlled variable transmission (ECVT) modes, which change based on the car's speed and engine demand. The result, according to GM, is a 40 percent improvement in city fuel economy over the gasoline-only Yukon, and a 25 percent improvement in overall gas mileage.
We took a ride along with GM this week in the 2008 Yukon Hybrid and got a first-hand impression of the next big thing in the hybrid world.


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[/FONT]
 
The 2-Mode is a nice approach in my opinion. It allows for gear lock up and not only electric motors so when one is at freeway speeds the motros do not have to spin even when they are not prodcing any energy to the wheels. They still would be spinning mass. The 2 mode allos for the motors to not spin when the IC engine would be engaged.


[FONT=&quot]GM's 2-Mode 2008 [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot] Hybrid[/FONT]
[FONT=&quot]Kevin Massy[/FONT]
[FONT=&quot]CNET Reviews[/FONT]
[FONT=&quot]Full hybrids have to date been almost synonymous with [/FONT][FONT=&quot]Toyota[/FONT][FONT=&quot]'s Hybrid Synergy Drive (HSD) system, which, in addition to being the technology behind all [/FONT][FONT=&quot]Toyota[/FONT][FONT=&quot] and Lexus hybrids, is licensed by Nissan for its [/FONT][FONT=&quot]Altima Hybrid[/FONT][FONT=&quot] and is used in a modified version by Ford in the [/FONT][FONT=&quot]Ford Escape[/FONT][FONT=&quot] and [/FONT][FONT=&quot]Mercury Mariner [/FONT][FONT=&quot]hybrids. This hybrid monopoly is about to change, however, as GM readies its 2-Mode hybrid system for introduction later this year in the Yukon Hybrid and Tahoe Hybrid SUVs. Like HSD, GM's 2-Mode system enables cars to run just on electricity, just on gasoline, or a mixture of the two. The system makes use of a two electrically controlled variable transmission (ECVT) modes, which change based on the car's speed and engine demand. The result, according to GM, is a 40 percent improvement in city fuel economy over the gasoline-only [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot], and a 25 percent improvement in overall gas mileage. [/FONT]
[FONT=&quot]We took a ride along with GM this week in the 2008 Yukon Hybrid and got a first-hand impression of the next big thing in the hybrid world.
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[/FONT]
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[FONT=&quot]Close-up of the 2008 GMC [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot] Hybrid[/FONT]
[FONT=&quot]GM's two-mode hybrid system is the biggest news in the hybrid world since the introduction of [/FONT][FONT=&quot]Toyota[/FONT][FONT=&quot]'s wildly successful [/FONT][FONT=&quot]Hybrid Synergy Drive[/FONT][FONT=&quot]. The two-mode system, which will debut later this year in the GMC Yukon and the Chevy Tahoe, makes use of advanced drive train technology to improve the mileage and the environmental image of two of [/FONT][FONT=&quot]Detroit[/FONT][FONT=&quot]'s most popular full-size SUVs.[/FONT]

[FONT=&quot]2008 [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot] Hybrid[/FONT]
[FONT=&quot]According to GM, the 2008 Yukon Hybrid will achieve a 40 percent improvement in city fuel economy over its gasoline-only counterpart. The hybrid will be less than 100 pounds heavier than the standard [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot], and will come with a lower price tag than the top-of-the range gasoline-only [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot]. [/FONT]

[FONT=&quot]High-tech transmission[/FONT]
[FONT=&quot]GM's two-mode Yukon Hybrid makes use of some sophisticated drive train technology. In place of the regular Yukon's automatic gearbox, the hybrid gets four fixed gear ratios and two electronically variable transmission (ECVT) modes that make use of planetary gear sets --thus the "two-mode" tag. The first ECVT mode operates with the vehicle in electric-only drive mode and through the second fixed gear ratio. The second ECVT mode kicks in after the second fixed-gear ratio. Thirteen processors located throughout the vehicle constantly monitor driving conditions, terrain, and driver inputs to make a decision on the optimum drive train configuration.[/FONT]

[FONT=&quot]Heavier--but only just[/FONT]
[FONT=&quot]The [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot]'s hybrid system--including its lithium-ion battery pack and two electric motors--adds 400 pounds to the curb weight of the standard [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot]. However, due to a number of weight-saving devices--including the aluminum hood and lighter seat materials--the [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot] hybrid ends up being less than 100 pounds heavier. [/FONT]
[FONT=&quot]Under the hood[/FONT]
[FONT=&quot]Paradoxically, the Yukon Hybrid has a larger engine than the gasoline-only model. The model features a six-liter small-block V-8 compared with the (non-Denali) gasoline-only [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot]'s 5.3-liter engine. Nevertheless, GM maintains that the Yukon Hybrid achieves a 25 percent efficiency overall compared with its gasoline-only counterpart. [/FONT]

[FONT=&quot]Hybrid instruments[/FONT]
[FONT=&quot]Inside, the Yukon Hybrid features some specific cabin instruments that enable the driver to monitor the status of the hybrid system. As well as two specific gauges in the instrument cluster, the [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot] hybrid has a Priuslike flow chart on its in-dash LCD screen. [/FONT]

[FONT=&quot]Auto stop[/FONT]
[FONT=&quot]Like GMs "mild" hybrids (the Saturn Vue Green Line and the Aura Green Line), the Yukon Hybrid features an Auto Stop mode, which indicates that the gasoline engine is not running. Being a full hybrid, the [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot] can run in Auto Stop mode under electric power.[/FONT]
[FONT=&quot]Battery[/FONT][FONT=&quot] power[/FONT]
[FONT=&quot]Up to a speed of 32mph, the Yukon Hybrid can run solely under electric power via its 60-watt motor, which is fed by the battery pack mounted under the second-row seats. To achieve this speed, however, drivers need to apply gentle throttle inputs. [/FONT]

[FONT=&quot]Regeneration[/FONT]
[FONT=&quot]Like many other hybrid cars, the Yukon Hybrid features regenerative braking, which channels brake friction via the alternator to charge the battery. Additionally, the car makes use of regenerative deceleration, which does a similar thing by converting friction from the wheels into battery power when the driver releases the gas pedal.[/FONT]

[FONT=&quot]Hybrid power[/FONT]
[FONT=&quot]The Yukon Hybrid can run on hybrid power--gasoline engine plus electric motor--in two modes. In low-speed city driving, the car can split engine demand between both propulsion sources. At higher speeds, the electric motor assists the gasoline engine, which makes use of a number of electronic controls, such as Active Fuel Management (which closes off four of the engine's eight valves when demand is low); cam phasing; and late-intake valve closure.[/FONT]

[FONT=&quot]Electrical systems[/FONT]
[FONT=&quot]All electrical systems in the Yukon Hybrid are powered by the 300-volt battery. The car's air-conditioning system runs directly from the battery, while the rack-mounted power steering is stepped down to 24 volts and other cabin electronics run off a 12-volt circuit.[/FONT]

[FONT=&quot]New aerodynamics[/FONT]
[FONT=&quot]In addition to its high-tech drive train technology, the Yukon Hybrid features some unique aerodynamic modifications to reduce wind resistance and improve fuel economy. External design tweaks include a spoked front grille, an aluminum hood, and sealed-in headlight assemblies. The aerodynamic mods give the Yukon Hybrid a drag coefficient of 3.4 compared to the standard [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot]'s 0.365.[/FONT]

[FONT=&quot]Hybrid tweaks[/FONT]
[FONT=&quot]Specifically designed 12-spoke alloy wheels, special front and rear spoilers, and unique running boards all help to make the Yukon Hybrid lighter and more aerodynamic.[/FONT]

[FONT=&quot]Going places[/FONT]
[FONT=&quot]GM's two-mode hybrid system, which was developed in partnership with BMW and DaimlerChrysler, will later be expanded to the Cadillac Escalade and to the Silverado and Sierra pickups.[/FONT]
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More from a woman' perspective

[FONT=&quot]The Driving Woman[/FONT]
[FONT=&quot]Edmunds.com[/FONT]
[FONT=&quot]Joanne Helperin[/FONT]

[FONT=&quot]August 17, 2007[/FONT]

[FONT=&quot]2008 Chevrolet Tahoe and GMC [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot] Hybrids[/FONT]

[FONT=&quot]Up until now, folks who needed the towing capacity of a full-size SUV or a 5-8-passenger people-hauler that couild go off road couldn't make "green" part of their vocabulary. But General Motors new 2-mode hybrid systems is going to change all that with the 2008 Chevrolet Tahoe Hybrid and 2008 GMC Yukon Hybrid.[/FONT]

[FONT=&quot]I drove a development model of the Tahoe Hybrid yesterday and got the low-down on its stats from Mary Sipes, Vehicle Line Director for Full-Size SUVs:[/FONT]

[FONT=&quot]- 332-hp Vortec V8[/FONT]
[FONT=&quot]- 0-60 in less than 8.6 seconds[/FONT]
[FONT=&quot]- [/FONT][FONT=&quot]40% improvement in city fuel economy over a gas-powered Tahoe (meaning 20mpg)[/FONT]
[FONT=&quot]- [/FONT][FONT=&quot]Total of 25% improvement in fuel economy overall[/FONT]
[FONT=&quot]- [/FONT][FONT=&quot]Significantly Improved aerodynamics and low rolling-resistance tires[/FONT]

[FONT=&quot]The 2008 Tahoe Hybrid will on on sale in the 4th quarter of '07 and you should see models start to trickle into showrooms in November. Pricing hasn't been announced, but I was told that the hybrids will "not be the most expensive model we have," meaning, it's right up there with the LT, but not as expensive as the most expensive LT, which retails for $38.950. The hybrid is much the same as an LT in terms of amenities, and it includes a nav screen and rear camera as standard equipment.[/FONT]

[FONT=&quot]The Tahoe was easy to drive... plenty of power, comfortable... there's even that gigantic center console that actually holds a medium-sized purse or small backpack. GM calls it a "no excuses" hybrid, meaning it loses nothing in terms of power or performance compared to its gasoline cousins.[/FONT]

[FONT=&quot]I'll be curious to see who'll buy these trucks: soccer moms who care about the environment or construction crews sensitive to the price of gas. Perhaps both. It's just nice to know that GM is working to make the full-size SUV category, which it dominates, more fuel efficient. And, with GM shouting from the rooftops about ethanol, it's entirely likely that we'll see an ethanol-powered hybrid down the road.[/FONT]

[FONT=&quot]And the basics on how it works? Well, it's a "real" hybrid, rather than a "light" one. But rather than try to describe the 2-mode system myself, here's a clip from the release:[/FONT]


[FONT=&quot]Excerpt:[/FONT]

[FONT=&quot]The 2-Mode Hybrid System[/FONT]
[FONT=&quot]The 2-Mode design integrates proven automatic transmission technology with a patented hybrid-electric drive system to deliver the worldÂ’s first 2-mode full hybrid.[/FONT]

[FONT=&quot]In the first mode, at low speed and light loads, the vehicle can operate in three ways: electric power only, engine power only or in any combination of engine and electric power. When operating with electric power only, it provides all the fuel savings benefits of a full hybrid system. Leaving the engine shut off for extended periods of time and moving under electric power at low speed is key to reducing fuel consumption in heavy stop and go traffic. [/FONT]

[FONT=&quot]The second mode is used primarily at highway speeds. In addition to electric assist, the second mode provides full eight-cylinder engine power when conditions demand. [/FONT]

[FONT=&quot]The second mode integrates sophisticated electronic controls, such as Active Fuel Management, cam phasing, and late-intake valve closure, allowing even more efficient engine operation. [/FONT]

[FONT=&quot]The 2-mode system also allows for more compact packaging because its compact and powerful electric motors are designed to fit within the approximate space of a conventional automatic transmission – an efficiency advantage compared with today’s typical single-mode systems that rely on much larger electric motors[/FONT]
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...

[FONT=&quot]The Driving Woman[/FONT]
[FONT=&quot]Edmunds.com[/FONT]
[FONT=&quot]Joanne Helperin[/FONT]

[FONT=&quot]August 17, 2007[/FONT]

[FONT=&quot]2008 Chevrolet Tahoe and GMC [/FONT][FONT=&quot]Yukon[/FONT][FONT=&quot] Hybrids[/FONT]

[FONT=&quot]Up until now, folks who needed the towing capacity of a full-size SUV or a 5-8-passenger people-hauler that couild go off road couldn't make "green" part of their vocabulary. But General Motors new 2-mode hybrid systems is going to change all that with the 2008 Chevrolet Tahoe Hybrid and 2008 GMC Yukon Hybrid.[/FONT]

[FONT=&quot]I drove a development model of the Tahoe Hybrid yesterday and got the low-down on its stats from Mary Sipes, Vehicle Line Director for Full-Size SUVs:[/FONT]

[FONT=&quot]- 332-hp Vortec V8[/FONT]
[FONT=&quot]- 0-60 in less than 8.6 seconds[/FONT]
[FONT=&quot]- [/FONT][FONT=&quot]40% improvement in city fuel economy over a gas-powered Tahoe (meaning 20mpg)[/FONT]
[FONT=&quot]- [/FONT][FONT=&quot]Total of 25% improvement in fuel economy overall[/FONT]
[FONT=&quot]- [/FONT][FONT=&quot]Significantly Improved aerodynamics and low rolling-resistance tires[/FONT]

[FONT=&quot]The 2008 Tahoe Hybrid will on on sale in the 4th quarter of '07 and you should see models start to trickle into showrooms in November. Pricing hasn't been announced, but I was told that the hybrids will "not be the most expensive model we have," meaning, it's right up there with the LT, but not as expensive as the most expensive LT, which retails for $38.950. The hybrid is much the same as an LT in terms of amenities, and it includes a nav screen and rear camera as standard equipment.[/FONT]

[FONT=&quot]The Tahoe was easy to drive... plenty of power, comfortable... there's even that gigantic center console that actually holds a medium-sized purse or small backpack. GM calls it a "no excuses" hybrid, meaning it loses nothing in terms of power or performance compared to its gasoline cousins.[/FONT]

[FONT=&quot]I'll be curious to see who'll buy these trucks: soccer moms who care about the environment or construction crews sensitive to the price of gas. Perhaps both. It's just nice to know that GM is working to make the full-size SUV category, which it dominates, more fuel efficient. And, with GM shouting from the rooftops about ethanol, it's entirely likely that we'll see an ethanol-powered hybrid down the road.[/FONT]

[FONT=&quot]And the basics on how it works? Well, it's a "real" hybrid, rather than a "light" one. But rather than try to describe the 2-mode system myself, here's a clip from the release:[/FONT]


[FONT=&quot]Excerpt:[/FONT]

[FONT=&quot]The 2-Mode Hybrid System[/FONT]
[FONT=&quot]The 2-Mode design integrates proven automatic transmission technology with a patented hybrid-electric drive system to deliver the worldÂ’s first 2-mode full hybrid.[/FONT]

[FONT=&quot]In the first mode, at low speed and light loads, the vehicle can operate in three ways: electric power only, engine power only or in any combination of engine and electric power. When operating with electric power only, it provides all the fuel savings benefits of a full hybrid system. Leaving the engine shut off for extended periods of time and moving under electric power at low speed is key to reducing fuel consumption in heavy stop and go traffic. [/FONT]

[FONT=&quot]The second mode is used primarily at highway speeds. In addition to electric assist, the second mode provides full eight-cylinder engine power when conditions demand. [/FONT]

[FONT=&quot]The second mode integrates sophisticated electronic controls, such as Active Fuel Management, cam phasing, and late-intake valve closure, allowing even more efficient engine operation. [/FONT]

[FONT=&quot]The 2-mode system also allows for more compact packaging because its compact and powerful electric motors are designed to fit within the approximate space of a conventional automatic transmission – an efficiency advantage compared with today’s typical single-mode systems that rely on much larger electric motors[/FONT]
Click to expand...
 
...

First Look: GM hybrid SUVs coming at the right time
[FONT=&quot]Thursday, August 09, 2007[/FONT]
[FONT=&quot]By Don Hammonds, [/FONT][FONT=&quot]Pittsburgh[/FONT][FONT=&quot] Post-Gazette[/FONT]
[FONT=&quot]Timing is everything in the car and truck business. [/FONT]
[FONT=&quot]Introduce new products at the right time, and you just might sell a slew of them. And that's what might happen to General Motors. [/FONT]
[FONT=&quot]Against the backdrop of anguish over rising fuel prices and falling SUV sales, GM is introducing two new full-size hybrid SUVs, the Chevy Tahoe and the GMC Yukon. [/FONT]
[FONT=&quot]Both get about 25 percent better fuel economy in combined city-highway driving, and about 40 percent better mileage in city driving. Although figures have not been set by the EPA, GM said the pair could get about 20 mpg in the city, about 22 on the highway, and about 21 overall. [/FONT]
[FONT=&quot]While those figures may not seem like much in the days of hybrids that get 50 mpg, they certainly look good compared with other SUVs. [/FONT]
[FONT=&quot]And remember, we are talking about two really big trucks here. They can haul seven passengers with all their cargo, and tow 6,000 to 6,200 pounds. They also have the traction benefits that come with all-wheel drive. [/FONT]
[FONT=&quot]Competitively, that makes these two far and away the most economical full-size SUVs around. [/FONT]
[FONT=&quot]Power comes from a two-mode hybrid system. That is, the engine has two electric motors instead of one. That allows for more flexibility and more options to save gasoline. [/FONT]
[FONT=&quot]The SUV runs on electric power only, engine power only (a 6-liter, 332-horsepower V-8) or any combination of engine and electric power. In lightning quick calculations, the SUV automatically decides what is needed. [/FONT]
[FONT=&quot]The active fuel-management system allows the engine to shut down some cylinders when strong acceleration is not needed. [/FONT]
[FONT=&quot]The system also has electric power steering instead of a belt-driven system that uses more gas. [/FONT]
[FONT=&quot]Other steps intended to lighten the weight of these SUVs include changes to the seat design and lighting fixtures, aluminum hoods and liftgates, lightweight wheels and low rolling-resistance tires. [/FONT]
[FONT=&quot]Driving the hybrid Chevy Tahoe proved to be much like driving any Tahoe. It's quiet, comfortable and easy to handle in traffic. [/FONT]
[FONT=&quot]As you drive, a gauge helps you obtain the best mileage if you keep the arrow indicator in the [/FONT][FONT=&quot]noon[/FONT][FONT=&quot] to [/FONT][FONT=&quot]2 p.m.[/FONT][FONT=&quot] position. If you're curious what the truck's hybrid system is doing, there's an easy to understand graph on the navigation screen that illustrates which parts of the system are working and under what conditions. That's better than the bewildering bar graphs and charts used in other hybrids. [/FONT]
[FONT=&quot]Although the automaker has yet to announce prices for the hybrids, I expect them to be $1,000 to $2,000 more than a conventional model. [/FONT]
[FONT=&quot]Timing is everything in the car and truck business. [/FONT]
[FONT=&quot]Introduce new products at the right time, and you just might sell a slew of them. And that's what might happen to General Motors. [/FONT]
[FONT=&quot]Against the backdrop of anguish over rising fuel prices and falling SUV sales, GM is introducing two new full-size hybrid SUVs, the Chevy Tahoe and the GMC Yukon. [/FONT]
[FONT=&quot]Both get about 25 percent better fuel economy in combined city-highway driving, and about 40 percent better mileage in city driving. Although figures have not been set by the EPA, GM said the pair could get about 20 mpg in the city, about 22 on the highway, and about 21 overall. [/FONT]
[FONT=&quot]While those figures may not seem like much in the days of hybrids that get 50 mpg, they certainly look good compared with other SUVs. [/FONT]
[FONT=&quot]And remember, we are talking about two really big trucks here. They can haul seven passengers with all their cargo, and tow 6,000 to 6,200 pounds. They also have the traction benefits that come with all-wheel drive. [/FONT]
[FONT=&quot]Competitively, that makes these two far and away the most economical full-size SUVs around. [/FONT]
[FONT=&quot]Power comes from a two-mode hybrid system. That is, the engine has two electric motors instead of one. That allows for more flexibility and more options to save gasoline. [/FONT]
[FONT=&quot]The SUV runs on electric power only, engine power only (a 6-liter, 332-horsepower V-8) or any combination of engine and electric power. In lightning quick calculations, the SUV automatically decides what is needed. [/FONT]
[FONT=&quot]The active fuel-management system allows the engine to shut down some cylinders when strong acceleration is not needed. [/FONT]
[FONT=&quot]The system also has electric power steering instead of a belt-driven system that uses more gas. [/FONT]
[FONT=&quot]Other steps intended to lighten the weight of these SUVs include changes to the seat design and lighting fixtures, aluminum hoods and liftgates, lightweight wheels and low rolling-resistance tires. [/FONT]
[FONT=&quot]Driving the hybrid Chevy Tahoe proved to be much like driving any Tahoe. It's quiet, comfortable and easy to handle in traffic. [/FONT]
[FONT=&quot]As you drive, a gauge helps you obtain the best mileage if you keep the arrow indicator in the [/FONT][FONT=&quot]noon[/FONT][FONT=&quot] to [/FONT][FONT=&quot]2 p.m.[/FONT][FONT=&quot] position. If you're curious what the truck's hybrid system is doing, there's an easy to understand graph on the navigation screen that illustrates which parts of the system are working and under what conditions. That's better than the bewildering bar graphs and charts used in other hybrids. [/FONT]
[FONT=&quot]Although the automaker has yet to announce prices for the hybrids, I expect them to be $1,000 to $2,000 more than a conventional model.[/FONT]
Click to expand...
 
...

GM's Hybrid SUV: Can It Slow Down Congress On CAFE Issue?
[FONT=&quot]Posted By:[/FONT][FONT=&quot]Phil LeBeau[/FONT]
[FONT=&quot]CNBC[/FONT]

7/24/2007
Today on Capitol Hill, GM will renew the auto industry's push to convince lawmakers that fuel efficient vehicles are on the way. Problem is, it may do little to slow down the CAFE express in Congress.
For years, the auto lobby was the strongest in D.C. and, for the most part, effectively limited Congress from passing aggressive fuel efficiency standards. But this time around, Congress, fueled by the impact of high gas prices, isn't going along for the ride. Seems Washington truly does want to force automakers to build cars and trucks that WILL get substantially better mileage.
So the automakers find themselves working harder than ever to convince Capitol Hill--and the American public-- that Detroit is trying to do more with less. Today, GM will show its two-mode hybrid Yukon; unlike most hybrids that only get electric motor assist and better mileage stopping and starting in the city, the Yukon Hybrid will also get electric motor assist on the highway and therefore use less gas cruising at higher speeds in Washington, D.C. Even though the new Yukon won't be out until later this year, GM is rolling out for lawmakers to make a point. That message: GM is committed to building cars and trucks with better mileage and lower emissions.
But here's the problem for the car companies. Despite the more fuel efficient vehicles they are building--and yes, they are building models that get better mileage--Congress wants more. There is a belief, right or wrong, that the automakers can crank out cars or trucks that deliver substantially better performance, with just a tweak or two of the engine.
But, it's not the simple. So the automakers will continue their efforts to educate Congress and the public about what the are doing.
Click to expand...
 
...
By Jeff Green
May 1, 2007

General Motors Corp.'s gasoline-electric large sport-utility vehicles will use a 6-liter engine to provide more towing power, as the automaker adds hybrids to compete with Toyota Motor Corp.

The gasoline-electric Chevrolet Tahoe and GMC Yukon, GM's biggest SUVS, will also be able to shut off half the engine's eight cylinders to reduce fuel use. The hybrid SUVs will be 25 percent more fuel-efficient than standard versions that have a 5.3-liter engine, said Mark Cieslak, chief engineer for the new models. The hybrids go on sale later this year.

“This is truly a developmental technology that moves the needle and raises the bar,'' Brett Smith, an analyst at the Center for Automotive Research in Ann Arbor, Michigan, said in an interview today after driving prototypes in Milford, Michigan. “Using the larger engine may hurt them somewhat with marketing to the green buyers. Environmentalists may not like it.''

GM plans to build at least 12 different hybrid models during the next few years as it tries to match offerings from Toyota. The Japan-based company passed GM as the world's largest automaker for the first time in the first quarter and may end GM's 76-year reign as the global leader this year.

Toyota sold the first hybrid in 1997. The gasoline-electric vehicles, led by Toyota's Prius car, reduce fuel use and emissions by combining a gasoline engine, an electric motor, a battery pack and brakes that capture energy from stopping. The components add about $3,000 to the price of such vehicles.

Hybrid sales in the U.S. have increased as average retail gasoline prices climbed above $3 a gallon the past two years. The average rose to $2.97 in the week through yesterday and has increased 27 percent since the start of this year, according to the U.S. government's survey.

Detroit-based GM is playing catch-up in the technology. Toyota said in June that it planned to double its hybrid models to 14 by early in the next decade and sell 1 million of them annually as early as 2010. GM's first hybrid SUV, the Saturn Vue Green Line, went on sale last year.

GM uses a so-called “two-mode'' hybrid system that lets it power larger vehicles like the Tahoe, which can hold as many as eight passengers and tow 6,000 pounds. Toyota doesn't have a hybrid version of its Sequoia large SUV.

With a smaller engine or limitations on towing, GM may have been able to make a stronger environmental statement, Smith said.

The Yukon gasoline models get 13 to 18 miles per gallon, according to U.S. Environmental Protection Agency fuel-economy ratings. GM doesn't have official figures for the hybrid version. The Prius rating is 60 mpg in the city and 51 mpg on the highway.

In city driving, most of the load is handled by the hybrid system. On the highway, the vehicles rely more on the gasoline engine. A computer switches among the different combinations of electric motors and eight- and four-cylinder gasoline engine operation, said Tim Grewe, the chief engineer on GM's system.

The automaker decided to use the 6-liter engine instead of the 5.3-liter engine on the hybrid because of towing requirements for the models, said Larry Nitz, executive director of powertrain engineering for GM's hybrids.

GM used an aluminum hood, liftgate and other parts as well as a thinner seat and smaller battery to help trim 400 pounds from the Tahoe. That went toward offsetting the added weight of the hybrid components. GM executives wouldn't say how much more it costs to build the new models.

U.S. hybrid sales rose 23 percent last year as total U.S. sales of cars and light trucks fell 2.6 percent. The 253,652 hybrids accounted for 1.5 percent of total sales of 16.6 million.

Toyota, based in Toyota City, Japan, dominated with 191,742 hybrid sales, followed by Tokyo-based Honda Motor Co. at 37,573. Ford Motor Co., based in Dearborn, Michigan, had 22,549, and GM sold 1,788 hybrid Saturn Vues.

GM, DaimlerChrysler AG and Bayerische Motoren Werke AG are spending more than $1 billion combined to develop hybrid models together, including the Tahoe and Yukon as well as Chrysler's Dodge Durango and Chrysler Aspen SUVs.
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