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GM Adds Two-Mode Hybrid Transmission to Saab BioPower Hybrid Concept

Advanced Hybrid System. Click to enlarge.

At the upcoming British International Motor Show, GM is unveiling a new version of the Saab BioPower Hybrid (earlier post) that incorporates an application of the two-mode hybrid transmission GM is co-developing with DaimlerChrysler and BMW Group.

The earlier version of the E100-capable flex-fuel hybrid, introduced at the Stockholm Motor Show, featured a 300-volt Li-ion battery pack, a 38kW rear-mounted electric motor (rear drive unit—RDU), a 15 kW integrated starter/generator (ISG) and all-wheel-drive with electric power transmission to the rear wheels. It was also widely believed to incorporate the capability for plug-in recharging, although GM/Saab declined to confirm that.

The E100 Biopower Hybrid concept now features the two-mode hybrid transmission.

The two-mode BioPower Hybrid Concept builds on this by incorporating the two-mode transmission while keeping the RDU. The new version of the concept thus combines an all-aluminum flex-fuel engine capable of generating 260 hp (191 kW) with three electric motors that can generate a total of 148 kW. As a result, the Saab BioPower Hybrid Concept provides significantly greater torque than its gasoline-only equivalent.

Although it has the potential to run on E100, the BioPower engine can use any combination of gasoline and bioethanol.

The two-mode hybrid offers torque boosting electric power assistance on demand, fuel-saving stop/start functionality, regenerative braking, seamless gear changing from the continuously variable transmission modes and an electric-only Zero Mode option for city driving.

This concept allows us to evaluate and explore the potential of hybrid technology in combination with BioPower. As part of this process, we are now developing our expertise further by introducing the two-mode hybrid technology. It shows how we can continue to express the sporty performance associated with Saab while using renewable resources and saving energy overall.

—Jan Åke Jonsson, Saab Automobile Managing Director

Hybrid Transmission. The hybrid transmission combines two 55 kW electric motors and four fixed gears within a single transmission housing. Commonly described as a two-mode hybrid due to the low- and high-speed electric continuously variable transmission (ECVT) modes, the system also incorporates four fixed gear ratios for a total of six operating functions. (Earlier post.)

The two-mode hybrid’s electric motors can be used for electric-only propulsion, boosting the internal combustion engine and providing regenerative braking.

Additional fuel-saving efforts include removing auxiliary functions, such as the water pump, air conditioning and power steering systems, from the engine’s belt drive and transferring them to electric power through the hybrid system.

The two-mode hybrid transmission is similar in size to a conventional automatic transmission. Its adaptable design allows it to be scaled to the size, mass and performance needs of various engines and vehicles. GM has announced that it will apply the two-mode transmission to hybrid versions of its full-size SUVs starting in 2007.

Engine. The engine is a BioPower evolution of the current all-aluminum, 16-valve 2.0-liter turbo engine in the Saab 9-3 range. Utilizing the higher octane ratings offered by E100, it develops 260 hp (191 kW) and 375 Nm (277 lb-ft) maximum torque, an increase of 24% and 25%, respectively, compared to its gasoline-only equivalent.

A Spark Ignited Direct Injection (SIDI) system provides optimum combustion with E100, to enable the same cold-starting performance as a gasoline engine. Variable inlet and exhaust cam phasing is used for optimum air flow and more durable valves and valve seats are fitted, together with bioethanol-compatible materials for the fuel system.

RDU. The RDU features a 38 kW motor, located between the rear wheels, which powers a transmission differential and drive shafts. Under acceleration at low speeds, the RDU is able to briefly generate 665 Nm of additional torque. The motor is also configured to provide regenerative braking and energy recovery from the rotating drive shafts during deceleration.

Battery. Energy storage for all three electric motors is provided by a high-capacity 300-volt lithium-ion battery with fan cooling. This is packaged under the floor of the trunk, without eliminating storage space. Battery performance is carefully monitored and governed by a dedicated electronic control unit.

Zero Mode. The driver can select Zero Mode via a button in the central console. At speeds below 50 kph (31 mph), Zero Mode will shut off the engine and switch the car over to electric power only from the RDU. In this mode, the battery bank provides a range of between 10 and 20 kilometers (6 to 12 miles). The engine is smoothly re-engaged whenever the battery status approaches a low charge level or the electronic throttle opening requires acceleration beyond the 50 kph operating limit.



Cool, a 6-12 mile EV range is plug-in hybrid territory.

Regarding their guarded response as to whether there will be a plug-in option or not - I think it's telling that there is so much EV range. If we guess that 6-12 miles would require 2-3 kWh of storage, then there should be say 3-4 kWh of storage to allow cycling within 75% SOC. Not much point having all that capacity in a ICE-hybrid system only - so I'm guessing that there should surely be some plug-in operation being researched here.


Where can I sign up to be a beta tester?


6-12 miles EV range ... that's all I need for bringing home the groceries. But then I never could afford a Saab. All I need now is the same range in something like a prius.


Mike, any idea on fuel consumption, E100 v gas? There's a huge debate raging on The Oil Drum about this. Most EPA figures show a 30% mpg hit when using E85. IIRC, the non-hybrid Saab Bio-Power has overall 12.5% mpg cost using E85 (but with more power and torque).

Seems like one could have an equivalent engine (using less cc) for an E85 powered vehicle with no mpg penalty. Any comments? Rafael?


If you had two engines with the same hp. One is made for 100% gasoline and the other for 100% ethanol (giving the ethanol motor a higher compression ratio and smaller size to maintain the same horsepower between the two) you would still go further on a gallon of gas. The disparity in energy content will not be made up in the increased thermal efficiency of a higher compression ratio engine.

When you throw a turbocharger in the mix it becomes a little different since off-boost the difference in compression ratio (for standard port injection) and/or the capability to downsize a turbo ethanol motor more than a turbo gasoline motor (due to running higher peak boost)...well, in that case I am not sure how much the difference would be.

allen Z

Dang It! Looks like not all of management has their heads in the sand. Now do the same/better setup with their other cars (Aveo, Impala, Corvette, etc). It also is nice way to get 4WD without the driveshaft.
___Another possiblity (for all automakers) is to use hydraulic/electric hybrid for cars/trucks. You get the regenerative energy surge recovery capacity and CVT of hydraulic, with the plugin capability of electric.


There's no reason in the world why a PHEV has to get 20 miles in EV mode. Even 5 miles would be very helpfull. You could upgrade later when batteries are cheaper.

Bob Bastard

Nice to see GM doing something that goes in the direction of sustainability for a change! This car takes on the problem of petroleum independence from multiple angles which is definately cool. LI-ion batteries and the transmission are a nice touch along with a cool engine design. One thing that seems as though it could be improved (other than the huge engine which seems to be a requisite for concept cars) is the rear motor setup. Instead of using a single motor with a differential, it seems as though two separate wheel motors similar to the ones used in the S10 ev would be more efficient, weigh less, and reduce the parts count. Obviously the control software for such a system would be alot more complex, but that should only provide a minimal concern for a company of this magnitude. The higher cost of the added parts would seem like much more of a concern if they are really serious about taking something similar to this to production. It would be interesting, also, to find out how much weight this system adds, and what the difference is in highway and overall fuel economy between the hybrid system and non-hybrid system. A Honda CR-X HF can achieve the same fuel economy as a Pious... err I mean Prius, simply from low weight, low drag coefficient, and small engine displacement.


quite interesting development on the part of GM. worth noting here that the electric motors are very powerful – almost as powerful as the main engine itself!


The car does have a plug-in capability.
"To optimise the availability of 'Zero Mode', a plug-in-feature is available which allows the battery bank to be connected to a mains electricity supply for additional charging in the garage. This would, for example, allow a driver commuting in heavy traffic to immediately resume in 'Zero Mode' the next morning after arriving home the previous evening having used up all its range. A neat socket is located behind the Saab badge on the 9-3 BioPower Hybrid Concept's trunk lid."

This press release was quickly recalled and BusinessWeek reported that they are waiting until January to make the official announcement, although the system will probably not be in a Saab at that point.


It looks like a good scheme. Weight may be a problem, they seem to have everything AND the kitchen sink in there.

It looks to be by far the best thing from GM lately.

Bob B: right. the single motor in the rear requiring a differential seems awkward.


One internal combustion engine and three electric motors? That's absolutely silly! Think about all of the materials and processes used to produce four motors for one vehicle, or how much would cost. This may be a solution for improving gas mileage, but to truly reduce the environmental impact of a car, a single efficient motor would be better, especially if it was driving a chassis designed to be lightweight and efficient from the ground up.

I just realized I'm basically describing the Loremo: Two cylinder turbodiesel, 450kg, 150mpg.

Well they kept the 38kW RearDriveUnit(seems like the best AWD solution ever) but the single 15kW ISG???thatll never do...bring on two 55kWers.
btw the current 2t motor gets ~24-34 on E10 with preference to 89-92RON.


The Saab 9-3 is basically the same platform as the Chev Malibu. C'mon GM get this in a product for the masses--where is the Malibu BioPower?

John Schreiber

The theoretical difference in fuel economy is 18% on E100 using this engine, factoring in nome of the other cool stuff. If the engine were sized to 1200cc performance would still be acceptable, and we might approach parity gallon for gallon. However these are the wrong questions. The correct question is what is the thermal efficiency of the engine. And in this case it is significantly better with E100 than E0. This is one of the best things about using BIOHOLS. We can increase thermal efficiency because the fuel is better.
If the fuel was water, would it matter if the fuel economy was 6 mpg? In my opinion the only way to look at fuel economy is BTU in / KW out. If it is the same or better than CLF (conventional liquid fuel) the point is moot, and the next question is where is my BIOHOL pump. (biohol is a term I coined that describes fermentation based, normally spark ignited fuels, as Ethanol is only one option. This allows me to include butanol and any other future molecule.) I suggest that others promoting these fuels consider using the term.


Thanx John. If we want "better" fuel, why not a B100 concept? The tankers roll we want E100 or B100?


when the electric car came out I thought great it's small enough and certainly not a new idea (been around since the 1900's) that it should be cheap enough for most of us to afford.
And then I heard the price tag $24000 for that tiny POS?!
And now the wonderful engineers at all the car companies are all coming up will bigger more creative NEWER ways to supposedly tackle the future gas shortage.
And all I here is a combination of gas and ethanol as being all they can come up with.
We need to completley replace gas people it's choking all of us.
For fudges sake what about purely steam driven for god's sakes I mean it worked 100 years ago, I surely can't be the only one to think that getting away from gas compltely is the only real solution.

Larry Carnes

Wake up people. If we are to clean up our atmosphere and keep our driving freedom, we need to think outside the thermal efficiency box. The masses are looking for cost per mile and clean air in that order. If one fuel costs less per mile than another the masses will buy the less expensive fuel. The only way our nation can drive out of the oil drum is in low cost simple technology that the masses can afford.

John Schreiber

To Fred,
We want both fuels. In terms of yield per acre the biohol fuels will exceed Biodiesel production by at least a factor of 2, in the near term. If the fuel is biomass sourced, we are on the same team. B100 will not work in SI engines, and there is way too much infrastructure in place to stop producing them. A B100 concept vehicle would be cool.

And Larry, are you sure you are correct? Do you drive a Segway to work? Electric cars are cheaper per mile driven, as are CNG vehicles, and have been for some time. But where are they? Why do people buy SUV's?
My point is simply that biohols are better fuels than gasoline, allowing for increased thermal efficiency, and if we can wean ourselves from the corn model, they will cost less per mile driven, and improve the "well to wheel" greenhouse gas profile. Hopefully the masses will just simply wake up and refuse to purchase anything with a GEMPG (Gasoline Equivalent Miles per gallon) rating of less than 20.

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