|The new smart fortwo coupé.|
DaimlerChrysler unveiled the new gasoline- and diesel-powered smart fortwo city cars yesterday evening in Stuttgart, Germany. The company said it will introduce a micro-hybrid version (starter/generator with stop-start capability) on one of the models in 2007.
The new smart fortwo coupé and smart fortwo cabrio offer a range of new all-aluminum gasoline engines, developed in cooperation with Mitsubishi. Engine capacity has been increased from 0.7 to 1.0 liters. There are two naturally aspirated engine versions to choose from, delivering 45 or 52 kW (60 / 70 hp) respectively, and a turbo engine rated at 62 kW (83 hp). Torque for the gasoline models is 89 Nm (66 lb-ft), 92 Nm (68 lb-ft) and 121 Nm (89 lb-ft) respectively.
The 3-cylinder engine is mounted transversally in front of the rear axle, and is slanted at an angle of 45 degrees towards the rear. The cylinder barrels take the form of grey cast iron liners. Gas exchange is controlled by four valves per combustion chamber. The valves are controlled by separate intake and exhaust camshafts, via bucket tappets.
To allow high torque to be developed even at low engine speeds, the intake camshafts can be twisted electro-hydraulically against the exhaust camshafts (variable valve control). The camshafts are driven via a maintenance-free timing chain.
Because the masses being moved are low, there is no need for a balancer shaft—which would reduce the output of the engine. However, in the turbo version there is a torsional vibration damper on the crankshaft.
The maximum charge pressure is 0.5 bar, with control taking place via a wastegate valve in the turbocharger. To ensure a long service life, the charger is fitted with a water cooling system, while the charge air cooler is based on air/air technology and is located behind the transmission.
The gasoline engines comply with exhaust gas standard Euro 4. The naturally aspirated engines’ compression ratio is 11.5:1, while in the turbo engine it is 10:1.
In addition to the increase in power, the maximum speed has also been increased to 145 kph (90 mph)—10 kph more than the predecessor model.
Standard fuel consumption of the gasoline variants is less than five liters of fuel per 100 km (47 mpg US). From the end of 2007, DaimlerChrysler will offer a micro-hybrid version of the 52 kW smart engine with a starter-generator for stop-start functionality. This will reduce fuel consumption in city traffic by up to 13%, bring it to approximately 4.35 liters/100km (54 mpg US) under the appropriate conditions.
DaimlerChrysler enhanced the performance of the cdi diesel engine by 10%, resulting in output of 33 kW (44 hp). The diesel is also Euro-4 compliant. With fuel consumption of less than 3.5 l/100km (67 mpg US), the smart diesel emits only 90g/km of CO2.
Its diesel particle filter (open system), which stops more than 40% of soot emissions, is unique in its segment, according to DaimlerChrysler. As of 2008, the smart fortwo cdi will be available with a closed system.
All engines are linked to an automated manual five-speed transmission produced by Getrag that has also been re-engineered. In the new smart fortwo there is once again no clutch pedal, as this task is performed by an electric motor. If the shift lever on the centre console is briefly tapped forwards, the transmission will switch up a gear, and if it is drawn back, down a gear.
An automated gear program—standard on one model (passion) and optional on others (pure and pulse) is triggered by a small button on the shift lever which is preferred for use in stop-and-go traffic.