http://www.technologyreview.com/read...ztech&sc=&pg=1

"Some 500 engineers at GM, DaimlerChrysler, and BMW are developing a new transmission system that delivers EV-mode operation just like Toyota. The transmission will add one more trick: the system can also take the electric side of the drivetrain out of the loop and run in engine-only mode. Their two-mode hybrid transmission, patented in 1999 by GM and currently used in its hybrid buses, swaps out the motors with a set of fixed gears, locking the engine to the driveshaft. The electric motors help make the switch seamless by synchronizing the speed of the two sets of gears, but once the shift is done the motors are out of the picture. . . ."

I'd have felt a lot better about this description if it weren't for this photo:



What bothers me is the front disk assembly looks a lot like a torque converter. The words of the article don't make sense unless the motors are only there to set the relative gear speeds so they can lock-up AND that really is a torque converter used to bring the vehicle up to 'lock-up' speed.

The real test will be the EPA numbers. If the GM hybrid vehicles have better City performance than Highway performance, we'll know it is a serious hybrid electric. But if the Highway numbers come in worse (assuming the whole EPA numbers aren't gamed), then I'll smile and drive on by. Fortuantely there are non-USA mileage scales that are unlikly to change.

Bob Wilson

 

Maybe I'm reading it wrong, but it seems like the article essentially reads: "We've built this hybrid transmission, and what it does is disable the hybrid components as soon as the driver hits the gas pedal to accelerate."

Hmmmm... I thought a big chunk of the hybrid FE improvement came from the IMA/HSD helping the engine get up to highway speed.

Of course, it also seems like GM is still planning on putting 2-mode into huge hulks that won't benefit much from hybridization (ie... going from 16 MPG to 19MPG for "only" an extra $5,000 isn't all that compelling from either a financial or environmental standpoint.) Or, to put it another way: How come BAS gets a 20% improvement and is fairly inexpensive (as far as hybrid systems go) and 2-Mode only gets a 25% improvement while being a much more expensive and more complicated system?

 

The real test will be the EPA numbers. If the GM hybrid vehicles have better City performance than Highway performance, we'll know it is a serious hybrid electric. But if the Highway numbers come in worse (assuming the whole EPA numbers aren't gamed), then I'll smile and drive on by. Fortuantely there are non-USA mileage scales that are unlikly to change. [Bill Wilson]



I don't know if I'd use THAT as the benchmark. IMA is a fully-developed, robust hybrid system but the Civic's highway numbers are still slightly lower than the highway numbers (although the gap has closed from the first generation IMA).

 

There are degrees of hybridization and the ratio of City to Highway MPG is a good guide. City performance is improved by minimizing braking losses and regenerative braking capacity is a good indicator.

The other way to improve City MPG is to maximize ICE-transmission efficiency in partial power modes. This is best handled by keeping the ICE out of fuel inefficient modes with the electric motor systems. But when I see what looks like a torque converter, my skepticism sensors go on high alert.

I'm also bothered that the GM motors are described as handling a syncro function and the absence of electric motor power ratings. We can't tell if the motors have the ability to move a 4-5,000 lbs vehicle on their own or at least maintain a speed. But the tone of the article was 'superior mechanical engineering.'

As for the Honda IMA, a little larger motor and electrical system would be a good thing. Some of the Honda Insight modifications, mIMA, suggest the control laws could be improved too. But I haven't made a study of the IMA systems, just what I've read:

http://99mpg.com/

Bob Wilson