July 18, 2007
John Aebi-Magee

Mercedes has announced a new model of the popular "smart fortwo" car. With fuel consumption of just 3.3 liters per 100 kilometers (71mpg) and emissions of 88 grams of carbon dioxide per kilometer the new smart fortwo cdi is the most economical production car worldwide. The new cdi model is not available in the US and Mercedes has not announced release plans.

The consistent use of lightweight materials means that the diesel engine weighs in at just 86 kilograms. Entire weight without driver is 770KG (1697 pounds). The crankcase features a state-of-the-art diecast aluminum bedplate design and the cylinder head and cylinder head cover are likewise made of aluminum

Light Weight Translates into Fuel Efficiency

A full tank of fuel costs around 38.00 euros will take you approximately 1,000 kilometers (621 miles) without refueling. With an annual mileage of 15,000 kilometers drivers of a new smart fortwo cdi would only have to refuel 15 times a year.

World's Smallest Direct-Injection Diesel Engine

Engineers at Mercedes have improved the cdi engine. The power and torque have each increased by ten percent, while fuel consumption has decreased by around 13 percent. This is made possible by the world's smallest direct-injection diesel engine that boasts technology previously only found in larger capacity engines. A turbo-charger, charge-air cooling, electrically controlled and cooled exhaust gas recirculation, hydraulic compensation of valve clearance and a state-of-the-art light alloy construction are further features that identify the cdi engine as a high-tech package.

The three-cylinder engine has also adopted two-phase fuel injection from the CDI engines of its sister brand Mercedes-Benz. A few milliseconds before the main injection a small quantity of diesel is injected into the combustion chambers where it ignites and preheats the cylinders. This results in a quieter combustion noise level than an engine without this pilot injection. The electronic "brain" of the cdi engine – a high-performance micro-computer that controls the whole engine-transmission system – calculates how much fuel is needed and the interval at which pilot injection and main injection take place.

One of the Safest Cars in its Class

The cdi includes anti-lock braking system (ABS) with electronic brake-force distribution, electronic stability program (ESP®), brake assist, full-size airbags for driver and passenger, seat belts with belt tensioners and belt-force limiters, safety seats with integral seat belts and the sturdy tridion safety cell of which 50 percent consists of high-strength steel alloys and that has proved itself in the toughest crash tests. This extensive safety equipment makes the new smart fortwo one of the safest cars in its class.

Smart fortwo cdi at a glance:

• Cylinders/valves R3, 2 valves per cylinder
• Engine capacity 799 cc
• Bore/stroke 65.5 x 79 mm
• Power output 33 kW/45 bhp
• Max. torque 110 Nm at 2,000-2,500 rpm
• 0-100 km/h 19.8 s
• Maximum speed 135 km/h
• Comb. fuel consumption (NEDC) 3.3 l/100 km
• CO2 emissions 88 g/km

For more information, see Daimler Chrysler or SmartUSA.

Photos courtesy of SmartUSA.