General Motors unveiled its third variant of its electric vehicle architecture E-Flex, the Opel Flextreme, earlier this week. Its energy source is a battery that powers the electric motor. Another energy source on board – such as a hydrogen fuel-cell or combustion engine – provides more power to increase operating range. In the case of the Flextreme, this is a 1.3-liter CDTI diesel engine.

Electric propulsion and a combustion engine are used in a manner fundamentally different from that of conventional hybrid propulsion vehicles. Regardless of the Flextreme's operating mode, it is always electrically powered. The diesel engine is onboard solely to power the generator and charge the battery, always running in optimum operating range.

The Flextreme can be charged in around three hours via a standard 220 V electrical socket. A fully charged lithium-ion battery gives the concept car a range of around 55 km in purely electric operating mode. When the battery is run down and no electrical socket available, the Flextreme's common-rail diesel engine operates at constant rpm to provide electricity and recharge it. The journey need not be interrupted or stopped.

A commuter who lives within 50 kilometers from his workplace, and therefore has a round-trip commute of 100 km every day, would need no diesel and therefore emit zero CO2 with the Opel Flextreme. The only requirement is that he charges up his car each evening and during work. But even if the owner forgets to recharge or travels on vacation in the vehicle, the Flextreme remains economical: it emits less than 40 g/km CO2 in combustion mode, thanks to its efficient engine configured for generating electricity. This increases the car’s range.

Diesel Engine: Modern, Cylinder Pressure-Based Combustion Control

The concept car's diesel engine also features the newest technology to further reduce exhaust and noise emissions. The closed loop technology is used to control the combustion process.

High-speed Piezo sensors integrated in the glow plugs measure the pressure in the cylinder, so the injections can be matched to the actual combustion in real time. The
1.3-liter four-cylinder engine is the second unit from GM to feature this innovative system, after the 2.9-liter V6 engine displayed at the Geneva Motor Show.

E-Flex System: Flexibility for Propulsion Systems and Energy Sources

With the General Motors E-Flex concept, different propulsion systems can be fit into one uniform chassis with electric drive. The aim is to support global diversification of the "energy mix" and to establish the electricity power grid as an energy source.

"Our E-Flex strategy is attractive because we can use different propulsion systems in the same vehicle architecture, depending on which energy source is locally available," said Larry Burns, GM Vice President, Research & Development and Strategic Planning. "E-Flex ensures flexibility on two levels in terms of the propulsion system and the energy sources. We can extract hydrogen or electricity either from a wide range of renewable sources – such as wind, solar, geothermic, hydro or biofuel – or from traditional sources such as natural gas, coal, nuclear power, and even gasoline or diesel."

General Motors has already unveiled two further E-Flex variants this year:

• At the Detroit Motor Show in January 2007, the Chevrolet Volt debuted with a 1.0-liter three-cylinder turbo gasoline engine designed to operate on gasoline or E85, a mixture of 85 percent ethanol and 15 percent gasoline.
  
  
• At the Shanghai Motor Show in April 2007, GM presented the Chevrolet Volt with enhanced hydrogen fuel cell propulsion. With four kilograms of hydrogen on board,
  the fuel-cell powered Volt has a range of up to 480 kilometers.

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Source: General Motors