I have tried to research the technical side of GM's dual mode and it seems quite similar to Toyota's Synergy drive--two M/G that share load and generating. There are differences but it does look a lot like Synergy. If true, how can they claim a 25% mileage improvement when the Camry improvement or the Ford Escape (also "Synergy") improves around 15% ?

Thanks, Julian.

Without getting into all the technical information (not enough time) you need to look at it from this perspective......

What makes a Honda 2.0L engine different from a Toyotat 2.0L? They are both internal combustion engines, aluminum construction, fuel injection, SOHC or DOHC? The differences are in the details.

Now, some of the differences between Synergy and 2-Mode lie in the details. The whole point of 2-Mode is that it provides a significant amount of assist in highway mode, not just in low load city driving situations. It focuses on keeping the engine operating at its most efficient range in either situation.

Another difference is that the 2-Mode systemin the truck and SUV configurations are seamlessly linked with the Advanced Fuel Management (AFM) system introduced in GM pickups and SUVs and some GM sedans (Impala, Grand Prix, LaCrosse). This system shuts off half the engines cylinders when they are not needed to provide efficient horsepower or torque.

Peace,

Martin

I am NOT the official voice of GM with respect to Hybrid issues

I am NOT the official voice of GM with respect to Hybrid issues

I am NOT the official voice of GM with respect to Hybrid issues

The differences are the number of 'clutch' units and parts counts. The Synergy drive appears to have fewer moving parts than the GM dual-mode drive that also, if I understand the architecture, includes an internal set of shifted gears. The synergy drive has to balance power flows to achieve different gear ratios and a set of shifting ratio gears in the GM system avoids this 'gear ratio' energy flow (and loss.)
I have not made a study of these vehicles so this is speculation. We know the GM hybrid versions include advanced engine capabilities and probably clever programming to keep the ICE in efficient speed and power regions. There is some data with my Prius (and by association the Ford Escape and Camry) that energy inefficient regions may be used more often than is desirable. Supporting evidence includes the performance claims of 'hypermilers' when we have accurate speed information along with their mileage claims.

For now, what makes sense is to take the EPA values for different vehicles at face value and wait until they get "in our hands." Speculating further at this time is sort of like asking before the baseball season, who will win the World Series?

Bob Wilson

ps. I didn't see Martin's posting until after posting mine. He hit <return> before I did. <grins>

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My mileage increased 25% or better with my TCH..

I'm attaching both the GM-Allison US patent on the 2-mode hybrid, as well as a paper comparing different hybrid formats (the paper contains some errors regarding the Toyota HSD vs the Ford FEH scheme). The paper discusses the benefits of 2-mode, but also shows that there are additional complexities and costs associated with the 2-mode scheme: (a) there are mechanical clutches involved (they should only operate when their input and output shafts are spinning at the same speed, however); (b) there are two full 3-shaft planetary gear sets involved.

Stan

Attached Files

	GM US patent #6478705 - 2-Mode hybrid transmission.pdf (67.8 KB, 5 views)
	Miller_HEV propulsion system architectures.pdf (758.5 KB, 3 views)

Thank you guys. Those are very helpful answers and they seem to indicate that GM is not doing a "me too" just to get around patents but has a significant design. I just built a retirement home and can't buy a new car until I sell a townhome; so I have plenty of time to wait for the reality show answers. Thanks again. Julian