Latest Industry News
VW Group DCT in Plug-in Hybrid and Free-wheeling Q3
Further proof of the versatility of the Volkswagen Group’s DSG dual clutch
transmission is given by two recent Audi presentations – that of the A3 e-tron
concept and the Q3 compact crossover SUV. Both were unveiled at the Shanghai
Auto show in April. The Q3 is to be manufactured in quantity in Spain, whereas
the A3 provides stylistic and engineering clues to the upcoming next-generation
A3. The first two generations of A3 have been hatchbacks; with the third
iteration, the idea of a sedan is floated for the first time.
Describing the four-door sedan as an attractive technical study, Audi says that the A3 e-tron’s twin power plants – a 1.4 liter TFSI gasoline engine giving 211 hp and a 27 hp electric motor – give it a dynamic character while also allowing high fuel efficiency and a range of up to 54 km in its zero-emission battery mode. The seven-speed DCT, labeled S-tronic by Audi, is charged with blending the outputs of the two power sources. It incorporates both stop-start and energy recovery systems and is linked in to the intelligent thermal management system for optimum warm-up performance.
The 12 kW banks of lithium ion batteries are located behind the seats. They are charged by the energy recovery system while the vehicle is in motion and by the electricity mains when parked. Both automatic and manual transmission modes are available to the driver, and on battery power alone the A3 e-tron is claimed to offer a range of 54 km.
The Q3 compact SUV now going on sale takes the
technology of the seven-speed S-tronic dual clutch transmission a step further
with the introduction of coasting, allowing the vehicle to freewheel under
certain conditions to save fuel and reduce emissions.
Already equipped with stop-start and energy recovery systems, the Q3 will offer Quattro all-wheel drive and S-tronic in its more powerful versions. As in other applications of this transmission, the driver can change gears either automatically or manually via the optional wheel-mounted shift paddles. New on the Q3 is an efficiency mode, implemented via the Audi Drive Select system, also optional. In efficiency mode, the air conditioning and cruise control are regulated with the specific aim of saving fuel, and the transmission will disengage one of its clutches and allow the vehicle to roll freely when conditions permit.
These measures clearly help conserve kinetic energy and save fuel, though it is not yet clear how Audi is to program the freewheeling mode and which factors will trigger its switching in and out. Nevertheless, the ability to disengage the drive could later open the door to a further CO2-saving strategy – being able to also switch off the engine on coasting, an especially important capability for hybrids.
Some DCTs Save Fuel – But Others Don’t
Claims by suppliers and automakers that dual clutch transmissions are energy efficient are borne out in a recent survey of several dozen models by German enthusiast magazine auto, motor und sport. Comparing manual and automatic versions of each model, the magazine looked at the option cost for automatic transmission and the change in the fuel consumption that resulted. While in almost every instance the automatic version was heavier on fuel than its manual equivalent, sometimes by as much as 25 percent, when the automatic option was that of a dual clutch transmission the difference was either much closer or, in several cases, weighted in favor of the automatic.
Models proving more economical in DCT automatic form
included the BMW Z4 and Porsche 911 Carrera. The Audi A3 and VW Cross Polo
exactly matched their respective manuals’ consumption in DCT auto form.
Paradoxically, some DCT-equipped models proved slightly less economical than
their manual counterparts, though not to the exaggerated extent of a
conventional automatic. Examples include the Audi A4 3.0 TDI Quattro, the Ford
Mondeo and the Peugeot 4007 crossover with its Mitsubishi-sourced DCT. The Skoda
Octavia, VW Golf TDI 1.6 and Passat TDI Blue were also slightly less fuel
efficient as automatics.
It was also noted that, atypically, the Audi R8, with its single-clutch AMT, used less fuel than the manual version.
The Toyota iQ, with its CVT automatic, was slightly less economical than its manual counterpart, while alone among planetary automatics the new Mercedes E180 was lighter on fuel as an auto than a manual.
While the results among some DCT-equipped models may be inconsistent, with several not quite succeeding in the tough task of matching the manuals’ economy, a different choice of candidates could have yielded findings that demonstrated that even better figures were available through the intelligent shifting capabilities of a good DCT.
New to DCT
Two new sports coupés, one soon to enter production and the other shown as a concept but expected to be green-lighted for manufacture, include dual clutch transmissions in engineering specifications designed to appeal to enthusiast drivers.
The Hyundai Veloster has been doing the motor show circuit since early
this year and is the first production car from the Korean group to feature the
new in-house developed dry clutch DCT with six ratios. It is teamed with a 1.6
liter gasoline engine giving 140 hp and adds 30 kg to the 2+2-seater coupé’s
1170 kg curb weight. No performance figures have yet been released.
Alfa Romeo, for its part, wowed the crowds at the Geneva auto show with its shapely mid-engine 4C coupé concept, finished in an unusual semi-matte red/pink color. Using the same transverse 1750cc four cylinder engine and dry clutch DCT transmission combination as the front drive Giulietta sports hatchback but reconfigured for central positioning and rear wheel drive, the 4C Concept offers a modern take on compact Italian classics such as the Lancia Beta Monte Carlo and Fiat X1/9.
With over 200 horsepower and excellent torque from
the responsive MultiAir engine fed through the equally responsive Fiat-group DCT
transmission, the production version of the 4C Concept is sure to please Alfa’s
loyal sports car fan base when it goes on sale in 2012.
Story Filed: 6/07/2011
By Tony Lewin, managing editor DCTfacts.com