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Reducing fuel consumption is one of the top-priority environmental goals at Volvo Cars. One of the most promising projects in this sphere is the Integrated Starter Generator (ISG) demonstrated at the Frankfurt Motor Show 2001. "In urban driving with its many stops and starts, ISG can cut fuel consumption by as much as 20 percent, and thus make a corresponding cut in emissions," says Hans Gustavsson, who heads the Research, Development and Purchasing unit at Volvo Cars.

The ISG unit is installed between the engine and gearbox, linked directly to the crankshaft. ISG replaces both the starter motor and the alternator. In addition, ISG supplies power in operating conditions which would otherwise raise fuel consumption. The ISG system employs 42-volt technology and it has a separate battery that is placed in the spare wheel bay in the luggage compartment. "There is no need to develop a new car model or significantly modify an existing car - ISG can be integrated with most of our current car models. It's a very cost-efficient system compared with other solutions designed to benefit the environment such as hybrid cars," says Hans Gustavsson and adds: "A Volvo with ISG looks and behaves pretty much like the Volvo you already have. The only noticeable differences are that the engine stops as soon as the car comes to a standstill, and there are longer intervals between visits to the petrol station..."

The Engine Switches Off When the Car Comes to a Standstill
The most noticeable difference compared with a conventional car is that the engine in a car with ISG switches off completely when the car comes to a standstill, instead of continuing to use fuel at idling speed - for instance when waiting at a traffic light. When the traffic light turns green and the driver presses the accelerator to move off, the ISG car starts up instantly and almost noiselessly. ISG supplies the engine with additional power at the moment the car moves off, and also during acceleration - when the car would otherwise require an extra portion of fuel to be injected into the engine. For the user who drives a lot in urban traffic, this is clear evidence of the ISG car's environmental benefits. The engine simply is not used when the car is not moving.

More Alert than a Conventional Car
ISG remains active throughout the driving process, for example during overtaking or at other times when extra power is needed. "In certain situations, the ISG-equipped car feels even more alert than a corresponding car with conventional power. For instance, you can drive at low revs in a high gear. The basic principle behind ISG is that the combustion engine should work as little as possible in order to cut fuel consumption and exhaust emissions," says Hans Gustavsson.

The Battery Receives Free Energy
When you lift off the accelerator pedal to slow down, the car's forward movement powers the ISG unit, which in turn recharges the 42-volt batter with free energy. ISG is far more efficient than a conventional alternator, and this is another contributory factor to the low fuel consumption. This also means that systems such as the power steering and air conditioning, which in today's cars are powered by the combustion engine, can instead be powered by electricity. The air-conditioning system thus continues to remain active even when the engine switches off. This is a benefit that many of Volvo's competitors cannot offer in their own ISG projects.

42-volt Electrics Bring Additional Advantages
42-volt technology provides other benefits in addition to powering the ISG system. The higher voltage means that the new technology that is making increasing inroads into cars, for instance in the form of advanced safety and information systems, has a more secure current supply. In addition, it will be possible to integrate far more electrically-powered comfort-enhancing features. How about a cupholder that cools your soft drink - or keeps your coffee hot? All this is possible with 42-volt technology. Development is already under way, and in the Volvo Cars parent corporation, the Ford Motor Company, several major projects are being conducted in this area.

[SOURCE: Volvo Cars]
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