Alternative Drives: Three Versatile Hybrid Concepts
Intelligent starter-generator in the smart mhd
The smart fortwo mhd — the smallest player on the team — started the ball rolling when it hit the road in October 2007. The economical three-cylinder gasoline model, which produces 52 kW/71 hp, embodies one of the three hybrid concepts presented by Mercedes-Benz Cars at the IAA Motor Show in Frankfurt, Germany.
“mhd” stands for “micro hybrid drive,” the main feature of which is an intelligent start /stop mechanism that helps reduce fuel consumption — especially in cities. Here, the speedy little car uses up to 19 percent less fuel than its conventional counterpart.
The micro hybrid drive technology in the vehicle causes the engine to shut off automatically when the car brakes to a speed of eight kilometers per hour, leading on average to an eight-percent reduction in fuel consumption in the New European Driving Cycle. The standard fuel consumption of 4.7 liters per 100 kilometers is reduced in this mode by 0.4 liters per 100 kilometers. There is also a corresponding reduction in CO2 emissions from 112 grams to around 103 grams per kilometer.
The smart mhd always shuts down its engine completely when the vehicle is idling (e.g. at a red light), thereby avoiding unnecessary fuel consumption. The engine then starts up again when the driver removes his or her foot from the brake pedal. At the heart of the start/stop system, a special belt-driven starter-generator assumes the functions of the conventional starter and the alternator.
When the three-cylinder gasoline engine is running, the starter-generator operates as an alternator and generates? electricity for the vehicle’s power network and battery. When the gasoline engine, which develops up to 92 Nm, is off and needs to be started again, the starter-generator acts as a starter motor that quietly gets the engine going in fractions of a second.
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Intelligent start/stop system | |
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The smart fortwo micro hybrid drive shuts down its engine when idling, leading to fuel savings of eight percent in NEDC driving. | |
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Engine: | |
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Gasoline engine |
3-cylinder inline |
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Rated output |
52 kW / 71 hp |
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Max. torque |
92 Nm |
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Hybrid module: | |
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Type |
Belt-driven starter-generator |
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Max. torque |
42 Nm |
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Overall consumption: | |
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Consumption (NEDC) |
4.3 l/100 km |
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CO2 emissions |
103 g/km |
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