|The smart ev.|
DaimlerChrysler’s smart division has developed a series of concept test cars that incorporate a range of advanced and alternative-fuel technologies: gasoline and diesel hybrids, cng-fueled, and electric.
These follow on the premiere of the crosstown hybrid showcar concept presented at the Frankfurt auto show in September.
The crosstown hybrid. The crosstown smart car prototype combines an electric motor (with an output of up to 23 kW) with the 45 kW (61 hp) gasoline engine from the smart fortwo.
The result is a 15% reduction in fuel consumption to 4.3 liters of gasoline per 100 kilometers (55 mpg US). The smart crosstown furthermore offers approximately 10% better acceleration (the production car requires 15.5 seconds to accelerate from 0 to 100 km/h).
The mild hybrid system offers start-stop capability as well as assistance during acceleration and during gear changes.
Instead of using a conventional automatic transmission and torque converter, the smart crosstown works with a manual transmission mechanism including friction-disc clutch. The advantages of this compared with a fully automatic transmission lie in the much higher efficiency, lower weight, more compact dimensions and lower production costs.
However, unlike an automatic transmission, this principle causes traction interruptions between opening and closing the clutch for gear shifting. In the smart crosstown these are bridged by the electric motor. For a few tenths of a second it supplies the propulsion power needed, enabling harmonious, steady acceleration over the whole gear spectrum.
Regenerative braking recharges the battery.
|The smart test prototype vehicles.|
smart fortwo micro hybrid. A micro hybrid version of the smart fortwo uses a belt-driven starter generator in combination with the 45 kW (61 hp) gasoline engine to reduce fuel consumption by 5%.
The micro hybrid version offers no regenerative braking, nor any tractive assist. It does provide start-stop functionality.
With the micro hybrid the standard fuel consumption level of 4.7 litres per 100 kilometers (50 mpg US) is reduced by 0.25 litres to less than 4.5 liters (52 mpg US). In urban traffic, the smart fortwo micro hybrid uses a 13% less gasoline.
smart fortwo cdi hybrid. The diesel hybrid version of the smart car consumes just 2.9 liters of fuel/100 km (81 mpg US).
The diesel hybrid combines a 20 kW electric motor with the 30 kW (40 hp) diesel engine. The design is much the same as crosstown hybrid, with the electric motor providing start-stop functionality, drive assistance, shift delay bridging and regenerative braking.
Because the car’s shift delays are bridged by the electric motor, it only needs 17.8 seconds to accelerate from zero to 100 km/h. That’s ten percent—two seconds—better than with a conventional diesel drive.
smart fortwo ev. The smart fortwo electric vehicle is driven solely by its electric motor with an output of up to 30 kW (41 hp). With a consumption of 12 kWh per 100 kilometers, the car has a range of 110 kilometers (62 miles).
A full recharge takes 8 hours; charing from 20% to 80% capacity takes four hours.
smart created the electric drive in cooperation with Zytek, a British company that focuses on developing hybrid and electric drives.
smart fortwo cng. The bi-fuel version of the smart allows drivers to choose between gasoline or natural gas drive. The modular design of the fuel system means that the entire high-pressure natural gas tank (2 x 16 litres) and the petrol tank (12 litres) fit in the car’s underbody. The volume of the car’s interior and luggage compartment remain, as in the case of the electric drive model, unimpaired.
The car consumes approximately 3.2 kilograms of natural gas (or 4.7 liter of petrol) per 100 kilometers, giving it a range of 385 kilometers (239 miles)—138 km with natural gas, and 255 km with gasoline. The gasoline model, with a tank volume of 33 litres, can, on a purely calculative basis, travel some 700 kilometers without a fuel stop.
|smart Hybrid and Alt-Fuel Prototypes|
|Engine Power||45 kW||45 kW||30 kW||–||45 kW|
|Motor Power||23 kW||20 kW||20 kW||30 kW||–|
|Fuel consumption||4.3 l/100km||4.5 l/100km||2.9 l/100km||–||3.2 kg CNG/100km|
4.7 l/100km gasoline
|Fuel economy||55 mpg US||52 mpg US||81 mpg US||–||3.2 kg CNG/100km|
50 mpg US gasoline
There is no commitment from smart to commercialize any of these—yet.