|2013 Beetle TDI. Click to enlarge.|
Volkswagen will bring the new Beetle TDI diesel (earlier post), unveiled at the Chicago Auto Show, to market in the US this summer as a 2013 model. Pricing of the diesel model, which is joining the gasoline-fueled Beetle 2.5L and Turbo in the lineup, will be announced closer to market launch.
From 1998 until 2006, the New Beetle was fitted with a 1.9-liter turbocharged four-cylinder diesel engine. Since then, this engine has been heavily revised to accommodate increasing demand for improvements in exhaust emissions and acoustics. One of the most fundamental improvements was converting the Pumpe Duse (unit injector) fuel-injection system to a common-rail design, as well as increasing the capacity by 72 cc thanks to a 1.5-mm wider bore. (Developed in cooperation with Bosch, the unit injectors were located at each cylinder to deliver the fuel for combustion.)
The new Beetle TDI uses the company’s 2.0-liter turbocharged, common-rail direct-injection Clean Diesel engine that delivers 140 hp (104 kW) and 236 lb-ft (320 N·m) of torque. VW estimates fuel economy of 29 mpg US city, 39 mpg highway (8.1 and 6.0 L/100 km, respectively).
The current engine features a cast-iron cylinder block and an aluminum-alloy cylinder head. It also utilizes some design elements that contribute to longevity and the reduction of noise, vibration, and harshness (NVH). The forged steel crankshaft, for example, uses four counterweights instead of eight to reduce bearing load and noise emissions. The pistons incorporate annular channels into which oil is sprayed for cooling the piston-ring zone. A pair of counter-rotating balancer shafts is situated below the crankshaft in the oil pan.
Dual overhead camshafts are driven via a toothed belt that also powers the coolant pump and the high-pressure fuel-injection pump. The cams themselves are linked by means of spur gears that have an integrated backlash adjuster that helps to ensure quiet operation. Each cylinder has two intake and two exhaust valves.
The TDI engine’s intake manifold uses flap valves that are powered by a step motor that is in turn activated by the Engine Control Module (ECM). At idle and low engine speeds, the flap valves are closed in order to cause high swirl into the combustion chamber, resulting in an optimal mixture. During regular driving, the flap valves are adjusted continuously according to load and engine speed to ensure optimum air movement; above 3000 rpm, the valves open fully for maximum filling of the combustion chamber.
The engine’s turbocharger features adjustable guide vanes that maintain the optimal aspect ratio for low- and high-speed performance. In order to meet current tailpipe emissions standards in all 50 states, the engine makes use of both high- and low-pressure exhaust gas recirculation over all engine speeds, as well as an exhaust system that has a particulate filter and no fewer than three catalytic convertors: for oxidation, oxides of nitrogen (NOx), and hydrogen sulfide.
The engine is mated to either a six-speed manual transmission or VW’s dual-clutch DSG six-speed automatic. DSG combines the comfort and ease-of-use of an automatic, with the responsiveness and economy of a manual. The six-speed, transversely-mounted DSG unit features two wet clutches with hydraulic pressure regulation. One clutch controls the odd gears—first, third, fifth and reverse—while the other operates the even gears.
With DSG, the set-up allows the next-higher gear to be engaged but remain on standby until it is actually selected. In other words, if the Beetle is being driven in third gear, fourth is selected but not yet activated. As soon as the ideal shift point is reached, the clutch on the third-gear side opens, the other clutch closes and fourth gear engages under accurate electronic supervision.
Since the opening and closing actions of the two clutches overlap, a smooth gearshift results and the entire shift process is completed in less than four-hundredths of a second. In addition to its fully automatic shift mode, DSG has a Tiptronic function to permit manual gear selection.
The 2012 Beetle is 71.2 inches wide (3.3 inches wider than the new Beetle), 58.5 inches tall (0.5 inches lower) and 168.4 inches long (7.3 inches longer). The new focal point is the C-pillar. The development team also increased the car’s track widths and wheelbase. The changed proportions give the Beetle a powerful and dynamic appearance. The TDI differs externally from the 2.5 and Turbo in having unique 17-inch aluminum-alloy wheels, TDI badging, and a chrome trim line that caps the top of the door’s sheetmetal.
Beetle TDI models are fitted with a strut-type front suspension with a lower control arm and a 22-mm-diameter anti-roll bar. At the back, there’s a torsion beam arrangement that has coil springs and telescopic dampers. Like the Beetle Turbo, the TDI uses rack-and-pinion steering with electric power assistance.
All Beetle models have standard anti-lock brakes (ABS) with electronic brake pressure distribution (EBD). The Beetle TDI has 11.3-inch-diameter vented front discs and 10.7-inch-diameter rear disc brakes.
The Beetle feature a rigid body structure that uses ultra-high-strength, hot-formed steels in the crash-load paths and seamless laser welds. Electronic Stability Control (ESC) is standard, as are driver and front passenger airbags and Side Curtain Protection airbags in front and rear. The Beetle includes Volkswagen’s advanced Intelligent Crash Response System that shuts off the fuel pump, unlocks the doors, and switches on the hazard lights if the car is involved in certain types of collision.
There are three Beetle TDI Clean Diesel trim lines: TDI; TDI with Sunroof; and TDI with Sunroof, Sound, and Navigation.