Author Topic: The smart fortwo cdi - big things come in small packages  (Read 1846 times)

Offline fasteddy

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The smart fortwo cdi - big things come in small packages
« on: January 23, 2007, 11:41:57 AM »
Toronto, Jan 19, 2007
smart, Mercedes-Benz and Maybach, are brands of the Mercedes Car Group of DaimlerChrysler AG, a company that has always been a leader in automotive technology and safety. This expertise has been passed onto the smart fortwo cdi coup? and cabriolet which have been developed since 1994 to provide a fun, comfortable, affordable and safe mode of transportation for individuals who seldom have a need for a back seat.

Research has shown that, on average, a car carries only 1.2 occupants to work. By these standards, the smart fortwo cdi is downright generous with comfortable room for two ? including all of their belongings. There are some bonuses to this design since; at just 2.5 metres long, smart owners will have no trouble finding a parking spot. In fact, two smart fortwos can fit in a single standard parking spot.

Body structure: the tridion safety cell

The most important consideration for a vehicle of this size is safety, and in the development of the smart fortwo, occupant safety was given top priority from day one. The core element of the smart fortwo crash management system is the high-strength tridion safety cell. In a collision, the tridion safety cell acts like a shield to protect both driver and passenger and at the same time ensures a very high standard of passenger safety. This rigid steel frame, reinforced with high-strength solid steel at important stress points, absorbs much of the impact energy. The cell?s transverse and lateral struts also transfer some impact energy to the crumple zones of the other vehicle involved in the collision.

Whereas the "hard shell" protects the occupant space, energy-absorbing safety features reduce the force applied on the occupants. These consist of short, but nonetheless extremely efficient deformation zones at the front and rear of the car.

smart restraint systems

In a severe impact, Emergency Tensioning Devices (ETD) automatically tighten the seat-belts in just a few milliseconds, ensuring that both the driver and passenger remain firmly secure in their seat. As a result, the occupants ?take part? in the deceleration of the vehicle earlier, and secondary impact forces are reduced. Then, in milliseconds, a belt force limiter controls the restraining action, reducing the risk of chest and shoulder injuries. In addition, the steering column collapses, absorbing energy and greatly increasing protection for the driver.

Sometimes small is safer

If another car hits a smart fortwo cdi from the side, the compactness of the smart fortwo cdi coup? and cabriolet is a great advantage. Thanks to the ultra-short wheelbase, the impact will almost always hit a wheel with the suspension behind it, providing excellent protection against intrusions into the occupant compartment.

Standard air bags

The smart fortwo cdi coup? and cabriolet also come equipped with standard full-size frontal air bags for both the driver and passenger as well as side air bags.

Front disc/rear drum brake system

The smart fortwo cdi has a front disc/rear drum brake system configuration with a standard electronic four channel anti-lock braking system (ABS) which also incorporates Electronic Brake Distribution (EBD) and Brake Assist (BAS).

Electronic Stability Program

The DaimlerChrysler relationship has yielded many other benefits, not the least of which is the Mercedes-Benz-developed Electronic Stability Program (ESP), which is standard in all smart vehicles and offers significant handling advantages. ESP? enhances driver control and helps maintain directional stability in turns as well as when driving straight ahead, including driving over uneven surfaces and even patchy snow, ice or gravel. The straight-line traction control function is integrated into ESP, which uses a steering angle sensor, speed sensors at each wheel, sensors for lateral acceleration (or lateral g-force) and vehicle yaw (the vehicle?s rotation on a vertical axis), and computer logic to calculate the path being steered versus the car?s actual path.

If there is a discernable difference between what the driver asks (through steering) and the vehicle?s path, ESP applies selective braking (braking one wheel, front or rear, left or right) to put the car back onto the driver?s intended path. ESP measures the tendency toward understeer (when the front resists steering changes causing ?plowing?) or oversteer (when the rear end ?fishtails?). When it senses understeer, ESP increases brake pressure to the inside rear wheel, while in over steering, it increases brake pressure to the outside front wheel. ESP is effective under acceleration, braking or coasting.

The smart fortwo cdi is the only car in the micro-car segment to offer ESP or a similar and equally effective system as a standard feature.

Outstanding results in all crash tests

Its unique crash management system makes the smart fortwo one of the safest cars in the micro-car segment. The smart fortwo's top position in regards to passive safety has been confirmed by more than 50 crash tests carried out in accordance with the same standards employed by Mercedes-Benz, as well as several independent accident simulations. Furthermore, the smart fortwo does not only comply with all legal safety requirements for occupants in passenger vehicles; it also fulfils the much more stringent DaimlerChrysler standards. The crash tests included the following: ? frontal crash at 65 km/h against a deformable barrier; ? rear-end crash at 55 km/h; ? side impact at 50 km/h; ? car-to-car crash where a smart fortwo and a Mercedes-Benz E-Class (which is twice as heavy) collided at a speed of 50 km/h in an offset frontal collision.

In every test, the strength and rigidity designed into the tridion safety cell provided greater occupant safety than in other small cars and the deformation values measured were below all internationally recognized standards for all vehicles and in some cases the results for smart were a long way below these standards (in this case, the lower the number, the better). This is particularly true in the case of a collision between the smart and a larger and heavier vehicle ? for example a collision with a Mercedes-Benz E-Class sedan.

The smart fortwo proved what it is capable of withstanding in the following tests: ? In 1998, the German motoring magazine AutoBild carried out a crash test on five small cars using the Euro NCAP method travelling into a deformable barrier at 64 km/h with a maximum vehicle deceleration of 32.6 g, concluding that passengers travelling in a smart fortwo would be by far the safest. The passenger cell was virtually unscathed with the A-pillar being displaced by only 20 mm. By comparison, other cars included in the same test had A-pillar displacement of between 25 and 61 mm ? up to three times that of the smart. The smart fortwo achieved the best results in all relevant areas of the car and showed a clear overall advantage over the competitive cars involved, as indicated in the following chart.

Measured Value smart fortwo other cars Reduction in footwell size (%) 21 26 to 39 Instrument panel penetration in mm 13 87 to 140 Pedal penetration in mm 15 85 to 186 Driver door opening force in Newtons 226 >500 to * Steering column displacement in mm** -84 / 18 59-91 / 45-118 * driver?s door opened on impact ** horizontal / vertical
In this comparative test, even the windshield of the smart remained intact. This is due to the extraordinary strength of the tridion safety cell.

Other crash tests provide further testimony

? In 1999, the Auto, Motor und Sport motoring magazine (edition 19/99) carried out a head-on crash test between a Mercedes-Benz S-Class and a smart fortwo, with both vehicles travelling at 50 km/h. They concluded that ?Despite its small size, the smart offers its occupants great safety potential." ? In June, 2003, the experts from DEKRA put a smart fortwo up against another small car in a head-on crash test, with both vehicles travelling at 50 km/h. The result was that while the passenger cell of the other car collapsed completely, the smart fortwo's rigid tridion safety cell remained intact. The smart fortwo driver, they concluded, would have survived with only minor injuries.
Crash tests also show low application of force on occupants

In the event of a frontal impact the extreme robustness of the smart passenger cell inevitably leads to high vehicle acceleration ? however the application of force on the occupants is in no way commensurate with this. Dangerous load peaks are avoided by the integrated timing and interaction of the seat belts, air bags and deformable steering column. Low head injury criteria values (driver 306, passenger 387, versus limit value of 1000), which measure the strain on the brain and head acceleration values of 51 g for the driver and 50 g for the passenger (versus limit value of 80 g) clearly demonstrate this.

The load on the thorax is also comparatively low. The corresponding values in the smart fortwo are just 41 g / 35 g leading to chest compression of 19 mm for the driver and 30 mm for the passenger. In other cars, values of up to 44 mm were measured on the crash test dummy driver.

Energy absorbing padding in the foot area, knee protection on the cockpit cross member, special safety seats with integrated seat belts with optimum belt guide, and the standard fast-triggering side air bags further reduce the risk of occupant injury.

Brake Assist

Another safety feature of the smart fortwo is the Brake Assist function (BAS). Research has shown that in an emergency situation, drivers tend not to brake hard enough or soon enough. Brake Assist senses panic stopping by the speed at which the driver depresses the brake pedal and automatically applies all available braking boost immediately. By helping to eliminate the delay caused by human intervention, Brake Assist can potentially reduce stopping distances when it matters most.

Cornering Brake Control

The ability of ESP to activate individual wheel brakes is the basis for a further safety function of ABS - Cornering Brake Control. During extreme cornering, the engine load on the wheel which is located on the inside during cornering is reduced and the cornering brake control function ensures that this wheel does not lock. If the driver brakes in such a situation, ESP senses that more braking power can be transferred to the other wheels than to the wheel with a reduced load.

Hill Start Assist

To make starting on a hill as comfortable as in cars equipped with an automatic transmission, the smart fortwo cdi coup? and cabriolet have a Hill Start Assist function. After releasing the brake pedal when stationary, Hill Start Assist keeps the wheels braked for 0.7 seconds. This leaves the driver enough time to move his or her foot from the brake to the accelerator pedal without the car rolling forwards or backwards. If the driver accelerates, the brake pressure is immediately released. This also protects the clutch and makes it possible to drive off without the assistance of the hand brake, even on steep slopes.

The cdi turbodiesel

The smart fortwo is equipped with a common-rail direct injection three-cylinder cdi turbocharged diesel engine that features low fuel consumption (4.2 litres/100km combined) and low emissions (90 g of carbon dioxide (CO2) per kilometre). It is the same technology used in the Mercedes-Benz E320 CDI?s 6-cylinder diesel engine, which provides ample power and torque for the smart fortwo cdi coup? and cabriolet.

A softip transmission allows the driver to change gears without using the clutch. This sequential 6-speed transmission changes up or down with a gentle tap on the shift lever. First gear is automatically engaged when the car is stationary.

Attention to details

The passenger and driver seats in the smart fortwo cdi are slightly staggered, ensuring that the driver has the same clear view out the passenger side.

The interior is spacious, providing ample elbow room, and the doors open wide making entry and egress easy and comfortable. The rear luggage compartment provides a generous 260 litres of cargo space. The back of the passenger seat also folds down flat to accommodate even larger items.

The smart fortwo cdi comes with body panels made of scratch proof polycarbonate plastic that are available in many colours. These panels do not rust, withstand light bumps without denting, and can be easily and quickly exchanged (at a cost) at any of the smart Centres.

The cabriolet offers an electric ?tritop? convertible roof which can be opened from a sliver to a wide-open top. An optional glass roof is also available on the coup?.


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