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GMC Graphyte SUV Hybrid-electric Concept Car
GMC's Graphyte concept vehicle boosts a Vortec 5.3 liter V-8 with Displacement on Demand technology mated to its new 'Dual Mode' hybrid electric transmission. The 300 hp SUV is projected to deliver a 25% improvement in fuel economy over a similar non-hybrid model, while offering full trail-towing capabilities. The drive train is similar to one that will be offered in 2007 in GM's Tahoe and Yukon SUV product line.

Dual of the Hybrids

One-on-one with Peter Savagian, General Motor's Dual Mode Hybrid Drive program engineering director

By Bill Moore

No, I didn't misspell the title.

This story is about a pair of General Motors concept vehicles propelled by what it calls its "Dual Mode" full-hybrid power trains; one incorporating a diesel engine and the other a gasoline engine. Intriguingly, the hybrid drive in one of the vehicles -- the diesel Opel Astra -- is mounted transversely, driving the front wheels, while the second -- the gasoline-engined Graphyte concept SUV -- drives the rear wheels through a conventional drive shaft-differential, demonstrating the flexibility of GM's approach.

But the story might just as easily be called "Duel of the Hybrids," pitting the current technology leaders Toyota, Honda and Ford against the relative "Johnny-come-latelies" at GM and DaimlerChrysler, who have only recently decided to concentrate their combined resources on what they consider the "Next Generation" hybrid drives.

EV World was fortunate to speak with the man leading the charge on the GM side of the newly-announced GM/DaimlerChrysler hybrid-electric drive train alliance, Peter Savagian, just a few days after his company debuted their hybrid concept cars at the 2005 North American Auto Show in Detroit.

My first question to Savagian was what exactly is a "dual mode" hybrid?

"Dual mode means we've got two separate connections in the hybrid system," he began, "one for low-speed, high load-type operations, and another for high-speed, freeway-type, lighter load-type operations". By that he means GM's hybrid drive, which fits inside a standard GM transmission case, is designed to bridge the efficiency gap found in current hybrid systems. Where Toyota and Ford's technologies are optimized for primarily city driving situations with lots and stop-and-go crawling along in bumper-to-bumper rush hour traffic, Honda's IMA is tailored for more highway driving conditions. While both systems offer significant fuel economy improvements, there is room for improvement over the entire driving regime.

What Savagian and his team claim to have achieved is the ability to offer both capabilities with a 25% fuel efficiency improvement overall. Of course, skeptics wonder why so little improvement, pointing to the fact that Ford's Escape Hybrid has demonstrated a 100% improvement turning in an impressive 37 mpg while tooling around Manhattan all day last year.

Still, GM's "Dual Mode" drive is an important first step for the world's largest carmaker. According to Savagian, the program began back in the 1990s as an outgrowth of work being done at Allison Transmissions, the people who pioneered the company's diesel-hybrid bus system.

"Last year, that hybrid powertrain represented about seven percent of the US transit bus market," he commented.

While "heavy hybrid" development continues at Allison, GM moved a significant part of the "know-how" -- i.e. engineers and their families -- to Detroit to join its Powertrain Group, which is responsible for the Tahoe/Yukon hybrid programs, as well as its light duty vehicle initiatives such as the previously announced "mild hybrid" Saturn Vue due out in 2006.

Integrated ZEV Mode
What makes GM's "Dual Mode" drive unique in the industry is its adaptability, according to Savagian. The key technology is a pair of small electric motors that fit neatly into the space usually occupied by an automatic transmission.

"We're able to get the motors down to a small enough size that we can put the whole thing, the hybrid transmission, into the space where an automatic normally goes. That gets us into a wide variety of applications without having to tear-up the vehicle or make a custom model specifically designated to be hybrid. We can fit the smaller front drive-type vehicle, the larger front drives; even the longitudinal-type passenger cars and trucks".

"We can fit the 'Dual Mode' in a space a normal trans-axle would go, east-west for front wheel drive, or north-south for rear wheel drive".

Like Toyota and Ford, GM's Dual Mode system can propel the car on battery power alone with the gasoline or -- in the Opel Astra's case -- the diesel engine turned off, though Savagian told me GM's engineers hadn't really determined what the operating range might be in electric-only mode.

Teaming with DaimlerChrysler
In mid-December, 2004 GM and DaimlerChrysler jointly announced that they would be teaming up to develop an advanced hybrid-drive system, presumably to not only share intellectual "horsepower" but also the costs.

"They saw the same kind of benefits, both good fuel economy, city and highway; and also the ability to go across a range of vehicle applications. So, we agreed to pool together our intellectual horsepower to move forward for applications whether they're badged Chrysler or Mercedes, or Chevrolet or GMC".

While the fine print of the arrangement have not yet been worked out, what is known is that the the 'Dual Mode' system will be the launch point for the effort. Savagian speculated that there probably would be "family similarities" found in the systems that evolve from the program.

In addition to sharing development costs, the object of the joint effort is to also speed up development for both companies, who are clearly feeling the heat from their Japanese rivals.

"Developing a hybrid is a big undertaking," he told me," and we can share the costs of doing that together. We can pull together our accumulative talent and intellectual property, and we think that will get us to better hybrids, sooner for both companies".

Opel Astra Dual Mode Hybrid concept

Diesel Hybrid Opel Astra
The Opel Astra is a production car in Europe. The reason GM selected it was to demonstrate that its system could fit into a small engine compartment built to house a transverse gasoline or diesel engine. The show car is equipped with a 1.7 liter CDTI diesel engine and a 300 volt, nickel metal hydride battery pack. GM is projecting that the car will get 25% better fuel economy than a comparable diesel-only model, which may help break down European resistance to hybrids.

Up to this point, European drivers have been reluctant to buy gasoline hybrids when diesels give them essentially the same performance and the fuel costs less. Savagian is convinced that mating diesels and hybrids will solve this problem because together they offer better fuel economy, which is important countries where petrol costs two to three times what it does in North America.

"A diesel hybrid would put all the benefits of hybridization fuel economy on top of just being a conventionally-powered diesel vehicle. So, the fuel economy now comes back. It's really the best-of-all situations in terms of fuel economy... you get the benefits of the diesel combustion and, in addition, the benefits of hybridization".

Savagian explained that this is an engineering exercise to show the flexibility of the 'Dual Mode' system, and part from some expected calibration issues, the drive handled the little turbo-diesel's torque just fine.

I asked him whether GM was -- like Ford -- working on a PZEV diesel. He responded that he could not comment on that, which immediately suggests, of course, that they are, especially given European greenhouse gas reduction initiatives.

Graphyte Concept SUV Hybrid
Where turbo diesels quicken European pulses, on this side of the Atlantic, its SUVs (only God knows why). So, the folks that gave the world the Suburban and the Hummer would be expected to roll-out a concept SUV and GM didn't disappoint, at least SUV fans.

The Graphyte is a futuristic sport Ute mounted on a truck chassis and powered by a 300 HP, gasoline-slurping, 5.3 liter Vortex V8 with "Displacement on Demand". Designed in GM's UK design studio, the Graphyte is intended to be a "no-compromise" family utility vehicle that can haul horses and ass, as needed.

It too is fitted with the 'Dual Mode' hybrid transmission, this time in a traditional "north-south" arrangement. As with the Opel Astra, GM is trying to show the flexibility of their system, clearly with an eye to competing with Toyota who has been openly offering its own Hybrid Synergy Drive to other automakers; Nissan being the first to license it for a hybrid version of the Altima due out sometime around the 2006 model year.

Savagian told EV World that it is this very similar to the gasoline-electric drive system that GM plans to offer first in Tahoe and Yukon SUV product line during the 2007 calendar year.

"We took two book ends of packages, a small front-drive with a diesel, all the way out to the large SUV in a longitudinal package."

No Plug-In Capabilities Planned
Despite having a 300 volt power supply -- which is twice that of Honda hybrids, but half that in the second generation Prius -- GM has no plans to offer a plug-in hybrid mode.

"We looked at it a while ago", Savagian responded. "I can say, at least from my years of working on a plug-in electric vehicle, the EV1, that that is a large undertaking, and generally, its kind of contrary to the philosophy here that we want to be able to offer a hybrid in a range of vehicles globally without upsetting the fundamental vehicle architecture. To the extend that we can find a good package, in addition to this hybrid transmission, we also have to find a place for the battery pack. And to have significant energy on board to have plug in capability, really means we have to start tearing up the car in ways we don't think is warranted. And the net benefit, we're kind of skeptical of, as well."

Mild Hybrids Coming To a Saturn Showroom Near You Besides the Dual Mode hybrids GM has announced, it is also evaluating other models that might be fitted someday with the system, but here all Savagian would say is that GM is considering its options.

Where the Tahoe/Yukon will be full hybrids, GM is also planning to roll out a "mild" hybrid initially in its Saturn car line in 2006. These will be belt-driven alternator/starter models that automatically turn the gasoline engine on and off at stop lights to conserve fuel, similar to the system offered in the Sierra pickup. It's a relatively inexpensive approach that offers some hybridization benefits, but no electric propulsion capabilities.

"We're a full line manufacturer with all kinds of customers and we think there's a business not only in the 'Dual Mode', full hybrid, we think that there's a business in simpler, less expensive... implementations of hybrid technology."

So, with GM rolling out 'Dual Mode' hybrids in 2007 and mild-hybrids in 2006, the field is going to start looking like a real horse race. That's good for the industry, for consumers and ultimately for the planet.

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Times Article Viewed: 16112
Published: 30-Jan-2005

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