Mother of all benchmarks
The parking lot outside the Hybrid Development Center looks like an automotive science experiment. It's filled with eviscerated hybrids of all kinds. GM, BMW and DaimlerChrysler engineers are benchmarking the performance of numerous competitors' hybrid vehicles. They dissected the mechanical and electrical systems to understand why they work so well.
Japanese-market right-hand-drive versions of the big Toyota Crown mild hybrid sedan and Estima all-wheel-drive minivan are parked near a partially dismembered Prius. A heavy black electrical cable dangles underneath the Crown.
In addition to the hybrid Toyotas, there's a Chevrolet S-10 electric pickup from the mid-1990s, one of GM's diesel-electric city buses and a Citroen C3, equipped with a diesel engine and a stop-start system. There also is a Ford Escape Hybrid minus its powertrain.
The Two-Mode transmission is not a copy of a Toyota transmission, nor does it use Toyota technology.
The basic design and layout of the Two-Mode is derived from GM's diesel-electric hybrid city buses developed in the mid-1990s.
GM's Nitz says the Two-Mode will be alone among hybrid transmissions. It can tow heavy loads, such as boats and horse trailers. And the way it shifts gears is different. When the transmission changes gears, the engine speed stays the same.
How the power is sent to the wheels, through a series of clutches and planetary gears, is another way the Two-Mode is better than existing hybrid transmissions, Nitz says.
In a conventional hybrid transmission, power is sent to the wheels through one or two paths: electrically through the motors or mechanically through the internal combustion engine. The electric path is less efficient, says Nitz.
"We get 100 percent of the engine power to the (wheels) through a mechanical path," he says. "We can boost power output electrically, or we can do regenerative braking off the electric motors, but they are not in the power path. That's a significant improvement. It enables full-displacement engines with reasonable-sized motors. It enables great towing and higher performance.
"If you pull other competitors' hybrids up mountain grades they tend to pull back power because they have to protect the electric motors. We just slip to a fixed gear ratio, decouple the motor and away we go," said Nitz.
One of the key aspects of the Two-Mode system is the powertrain's controller and the software in it -- the brains of the system. The controller keeps the engine running in what engineers call a "sweet spot" in the rpm range.
If more power is needed, say to propel the vehicle up a steep grade, the controller will keep the engine in the sweet spot but use the electric motors in the transmission for the extra power, said Steve Poulos, GM's hybrid powertrain chief engineer. "The whole goal is to always get your engine parked near that point," he said.
The Two-Mode transmission alone won't be responsible for the entire fuel economy gain, said Poulos. He said some of the gains come from a cylinder cutoff system that turns off half the V-8 engine at highway cruising speeds, the stop-start system that turns off the engine at stoplights and improved aerodynamics.
When the Two-Mode debuts in the fall, GM's biggest rival in the full-sized SUV segment, Ford, will not have a similar transmission or any full-sized hybrid SUV. Neither will any of the import brands.
But having no competition doesn't guarantee sales success, says Phil Gott, an analyst at Global Insight in Lexington, Mass.
Gott believes that, like the Prius and Honda hybrids, most drivers won't get anywhere near the EPA-rated fuel economy in an SUV equipped with the Two-Mode transmission.
"Very few automotive sales are made because of a transmission. The real question is: What is the impact of hybridization on the marketability of an SUV?"
So far, sales have not been good for hybrid SUVs. Toyota is having a tough time selling Highlander Hybrids and Ford has had to pile on incentives and crank up a big-time marketing campaign to ignite sales of the Escape Hybrid.
The Two-Mode project gives GM the chance to re-establish its reputation for engineering excellence, which it lost in the 1970s and 1980s because of disasters with diesel engines and other failed technologies.
Says Gott: "The fact that they offer hybrids will help assure in peoples' minds that GM is a current technology company. It will help bring people into the showroom. It will help give people confidence in the company, and it will help GM sell vehicles overall, even though most of them won't be hybrids."
BMW and DaimlerChrysler won't talk about their plans for the Two-Mode.
Epple, the BMW hybrid chief, said his company joined the partnership because BMW officials were impressed with the Two-Mode's potential and because it could get a version of the transmission faster and for less money than if it had developed or bought a similar transmission from a supplier.
Truckenbrodt, DaimlerChrysler's hybrid chief, agrees: "We are really building on a very good solution already. But it improves so much by adding the experience and the lessons learned and the competency from those various engineers."
The Two-Mode transmission also could be a way for German automakers to hedge their bets. If their plans for diesels in North America don't pan out, they will have the Two-Mode transmission to give them high fuel economy.
"Hybrids are one alternative in order to improve fuel economy," says Epple. "Nobody knows what is going to happen to diesel in the United States. The memory of the customer lasts for a long time. People don't forget," he said, referring to the lingering bad reputation of the diesels of the 1970s and early 1980s.
None of the automakers would talk about the financial aspects of the Two-Mode. But it is not likely to be sold for a profit, at least initially. Nitz said GM hybrids will debut with nickel-metal hydride batteries. Not until lithium-ion batteries become available around the end of the decade will automakers have a chance to take significant costs out of their hybrids, says Watson, the Ford hybrid engineer.
Says Epple: "The thinking and pride of engineers is once you produce something and have something on the drawing board, the ideas arise how it can be improved, modified and the costs can be reduced."
You may e-mail Richard Truett at [email protected]