|New Golf GTD. Click to enlarge.|
Volkswagen has introduced a new version of the Golf GTD (“Gran Turismo Diesel”) in Europe, and plans to bring it to the US market, reportedly likely for the 2016 model year. The latest GTD is based on the seventh-generation Golf (earlier post), and thus, on the strategic MQB (modular transverse matrix) platform. (Earlier post.) It thus becomes the first GTD built off of the MQB components set.
With a new 2.0L diesel delivering 184 horsepower (137 kW), 280 lb-ft (380 N·m) of torque, CO2 emissions of 109 g/km, and a NEDC combined fuel economy figure of 56 mpg US (4.2 l/100 km) when equipped with the six-speed manual transmission), the new A7 GTD is improved all around, with 14 more horsepower; an additional 22 pound-feet of torque; a 25 g/km improvement in CO2 emissions, and 10 mpg better fuel economy than its predecessor.
When equipped with a six-speed DSG dual-clutch automatic transmission, the GTD—the first GTD to have a stop/start system on board as standard—has an NEDC combined fuel economy figure of 52 mpg (4.5 l/100 km)—also a marked improvement over the A6 GTD’s 43 mpg. As a comparison, in 2007, the first-generation Golf BlueMotion (Volkswagen’s most fuel-efficient version) was regarded as having sensational gas mileage at 52 mpg—4 mpg worse than the new GTD, which has 79 more horsepower and is 25 mph faster.
The base version of the Golf GTD, at 3,036 pounds (1,377 kg), accelerates from 0 to 62 mph in 7.5 seconds and also accelerates from 50 to 75 mph in fifth gear in 7.5 sec. By comparison, the earlier A6 Golf GTD posted 8.1 and 8.0 seconds for the same tasks, respectively. Maximum speed has improved from 138 (222 km/h) to 143 mph (230 km/h).
Being based on the new modular transverse matrix (MQB) gives the new GTD more dynamic proportions. Compared to the previous model, the wheelbase was extended 2.1 inches to 103.6 inches, but at the same time the front overhang was shortened by 0.5 inches. Since the A-pillar has migrated towards the back of the car, the hood looks longer and the car has a premium “cab backwards” look. In addition, the proportions are sportier, because it is 1.1 inches lower (56.8 inches high), 2.2 inches longer (168.0 inches overall), and 0.5 inches wider (70.8 inches).
The GTD bodyshell now has 28% of parts in ultra-high-strength, hot-formed steel, up from 6% on the Golf A6.
New EA288 TDI engine
This new GTD features an entirely new EA288 common-rail direct-injection and turbocharged four-cylinder 2.0-liter TDI Clean Diesel engine that is transversely mounted, driving the front wheels. The engine delivers 184 horsepower at 3500 rpm and maximum torque of 280 pound-feet is developed at 1750 rpm. The engine has a compression ratio of 15.8:1.
In the MQB set, the EA288 four-cylinder covers engine displacements ranging from 1.6 to 2.0 liters. The Golf GTD uses the most powerful version of the 2.0 TDI, which conforms to the Euro-6 emissions standard.
The only dimensions this new 2.0-liter TDI engine shares with the previous EA288 are its 88-mm bore spacing, 81.0-mm bore, and 95.5-mm stroke. To handle the much greater complexity of the engine, Volkswagen developed entirely new software for the engine controller.
|Variable valve timing. Click to enlarge.|
Key features of the GTD engine include its variable valve timing (VVT), dual-loop exhaust gas recirculation (EGR), intercooler integrated in the intake manifold, the common-rail system that now operates at 29,000 psi (2,000 bar) instead of 26,000 psi (1,800 bar), and a new turbocharger.
Variable Valve Timing. The most important component for reducing internal emissions is variable valve timing, actuated by cam phasing. This enables the engine to achieve highly effective compression during cold start and hot running, low NOx and particulate emissions, and sustained strong chamber fill over the full load range.
|Dual-loop EGR system. Click to enlarge.|
New EGR system. The new dual-loop EGR system consists of a cooled low-pressure EGR system (LP-EGR) on the exhaust side and an uncooled high-pressure EGR system (HP-EGR) on the induction side.
The requirements of the Euro-6 emissions standard make it essential to attain further significant reductions in emissions immediately after a cold start. The primary solution is to utilize an uncooled high-pressure EGR; its higher induction air temperature improves combustion behavior and thereby ensures higher exhaust temperatures for accelerated response of the catalytic converter. This results in low engine-out HC emissions (hydrocarbons) with low NOx values.
In addition, mixing uncooled exhaust gas (HP-EGR) during low-rev driving prevents cooling of emissions control processes that can even occur with a hot engine. Meanwhile, the low-pressure EGR system plays out its advantages in the usual driving ranges up to the full-load range to assure effective NOx reduction even at higher load demands.
The HP-EGR loop is supplied via an integrated flange on the exhaust manifold; it routes the exhaust gas via a gas outlet in the cylinder head to the water-cooled HP-EGR valve, which is mounted on the outlet box of the intercooler integrated in the induction pipe. This direct component layout eliminates the EGR lines that were needed in the previous model. This arrangement also enables faster reactions to target value changes in the part-load range.
Revised common-rail injection. The GTD’s EA288 engine uses a Bosch common-rail system. The higher injection pressure allows, among other things, the injection time to be shortened. n turn this allowed more flexible configuration of the combustion process. The injection quantities are metered by further developed injectors with solenoid valves; compared to the previous injectors, they are characterized by considerably faster response.
Additional fuel volume in the form of a mini-rail in the injector body also minimizes pressure waves on the nozzle needles, which stabilizes the injection volumes. The nozzle needles used here also reduce CO2 and HC emissions and optimize EGR compatibility, further reducing NOx emissions.
|Location of the oxidation catalyst and particulate filter. Click to enlarge.|
Complex emissions control. To conform to the Euro-6 emissions standard, a NOx storage catalytic converter was placed upstream of the diesel particulate filter in the Golf GTD. The exhaust system has two lambda sensors and three integrated temperature sensors that supply the inputs for controlling the regeneration operating modes and exhaust gas temperatures. The oxidation catalytic convertor and particulate trap are now packaged close to engine for reduced emissions.
The US market version will use a urea SCR system to meet the more rigorous NOx requirements in this market, Volkswagen executives said during a briefing on the GTD in Berlin.
Balancer shafts for the GTD engine. The new diesel engine in the Golf GTD is not only very low in emissions, fuel-efficient, and torquey, it is also very smooth. This is achieved in part by the use of two balancer shafts with low-friction bearings.
Chassis and suspension
As in the new Golf GTI, the GTD has an entirely retuned sport suspension that has a 0.6-inch-lower ride height than a stock Golf A7. Like the new GTI, it shares a strut-type front suspension and a multi-link arrangement at the back, along with the XDS+ electronic differential lock and the new “Progressive Steering” system.
The latest generation of the Dynamic Chassis Control (DCC) adaptive damping system is also available in the “Sport & Sound” pack. (More on the Sport & Sound pack later.)XDS+. The XDS system that was first introduced in the Golf A6 was further developed into the advanced XDS+ system for the new Golf GTD (and the GTI).
Technically, the XDS+ electronic differential lock integrates with the Electronic Stability Control (ESC) to improve vehicle dynamics. The system electronically monitors input from various wheel sensors and, in the event of slippage, transfers extra torque to the front wheel with the most traction, thus improving handling and traction. XDS+ now uses rear brake input to reduce understeer.
ESC Sport. In the Golf GTD, Volkswagen is offering the “ESC Sport” function for very experienced drivers. The system is activated by a two-stage switch on the center console.
If the driver pushes the button once briefly, it deactivates the traction control. When the button is held longer than three seconds, Electronic Stability Control (ESC) switches to the “ESC Sport” mode, which has a higher threshold before intervention. The ESC can also be activated and de-activated by settings in the CAR menu as well as by the button on the center console.
“Progressive steering”. Another new feature on the GTD that is shared with the GTI is the so-called “Progressive Steering”, which features a variable steering ratio and a more powerful electric motor.
Where “normal” steering racks have teeth that are spaced consistently, the progressive system has a different tooth pitch in the center than it has on the outside. The lower steering ratio in the center means that the car responds more quickly when entering a turn and also reduces the amount of effort needed to turn the wheel at extreme steering lock, such as when parking. With this system, it only takes 2.1 turns to go from lock to lock; on less-powerful Golf models it takes 2.75 turns.
DCC dynamic chassis control. The GTD has an available second-generation Dynamic Chassis Control (DCC) adaptive damping system. This offers three driving modes—“Comfort”, “Normal” and “Sport”—which can now also be selected and displayed on the center console touchscreen via the “Driving profile selector”.
The DCC system adaptively regulates the damper valves via a refined Volkswagen control algorithm. DCC evaluates input signals from wheel displacement sensors and accelerometers as well as vehicle bus information from the Chassis-CAN bus. It then computes the optimal damper force for every driving situation and adaptively adjusts it, with the ability to apply different damping forces to each individual wheel.
A suite of safety and assistance features is available on the GTD as optional equipment. Among these are the PreCrash preventive occupant protection system; the Adaptive Cruise Control system (ACC) plus Front Assist with City Emergency Braking; Lane Assist lane-keeping assistant; road sign recognition; the latest generation of the ParkAssist parking assistant; and Light Assist and Dynamic Light Assist.
Other new technologies have been added such as a driving profile selector that has up to five programs—“Eco”, “Sport”, “Normal”, “Individual” and (in combination with DCC) “Comfort”.
Driver Alert system. This standard feature detects waning driver concentration and issues an acoustic warning signal that lasts five seconds. A visual message also appears on the instrument cluster recommending a break from driving. If the driver does not take a break within the next 15 minutes, the warning is repeated once.
At the beginning of each trip, the system analyses a range of factors, including the driver’s interaction with the steering: if there’s a deviation from the steering behavior recorded at the beginning of the trip, then the visual and acoustic warnings are produced.
Automatic Post-Collision Braking System. Another standard feature is the Automatic Post-Collision Braking System (APCBS), which has already won a safety innovation award from Germany’s largest automobile club (ADAC). The APCBS automatically slows the vehicle when it is involved in an accident in order to significantly reduce its residual kinetic energy. The system is triggered based on detection of a primary collision by the airbag sensors. Vehicle braking by means of the system is limited by the ESC control unit to a maximum rate of 0.6g.
The driver can override the APCBS at any time; for example, if the system recognizes that the driver is accelerating, it gets disabled. The automatic system is also deactivated if the driver initiates hard braking at an even higher rate of deceleration.
PreCrash preventive occupant protection. If this system detects that an accident may be about to happen—e.g., when hard braking is initiated—the front seatbelts are automatically pre-tensioned to ensure the best possible protection by the airbag and belt system.
When the system detects understeer or oversteer that’s severe enough to engage the stability control, the side windows are closed (except for a small gap) along with the sunroof. This is because the head and side airbags offer optimal support and effectiveness with the windows and sunroof almost fully closed.
Adaptive Cruise Control (ACC). Using a radar sensor integrated in the front of the car, this system has a speed range of 18 to 99 mph (29 to 159 km/h). ACC maintains the speed and a predefined distance to the vehicle ahead and will brake or accelerate automatically in flowing traffic. With the DSG transmission, ACC will bring the car to a standstill if the vehicle ahead stops and will then automatically restart on a prompt from the driver.
Front Assist system. This alerts the driver that braking is needed by visual and audible warnings. If the driver fails to brake hard enough, the system automatically applies enough braking force to avoid a collision. Should the driver fail to react, Front Assist automatically brakes the car to give the driver more time to react. Ideally, this lets the driver avoid an impending collision, or at least reduces the speed at impact. The system also alerts the driver if the car is getting too close to the vehicle in front.
City Emergency Braking. The City Emergency Braking function is an extension of Front Assist and monitors the area in front of the car using the ACC sensors. Below 18 mph, the brake system is preloaded, like it is with Front Assist, if the car is at risk of colliding with a moving or stationary vehicle ahead. If necessary, City Emergency Braking then automatically initiates hard retardation to reduce the severity of the impact. In addition, if the driver presses the brake pedal with insufficient force, the system assists with maximum braking power.
Lane Assist. This camera-based assistance system uses steering intervention to maintain the car’s position within the lane in the roadway. The system, seen for the first time in the Golf, can also maintain continuous lane tracking, helping to reduce stress.
Driving profile selector. A driving profile selector is now available for the first time in the Golf GTD. This features four programs—Eco, Sport, Normal, and Individual—on cars with the standard suspension, with a fifth program (Comfort) available on GTDs equipped with the DCC system.
Eco: the engine controller, air conditioning and other auxiliary units are controlled for optimal fuel economy. In addition, vehicles with the optional DSG transmission have an additional coasting function when the driver lifts off the throttle: the DSG disengages and the engine idles.
Sport: the damping is increased to further improve body control and the engine response and DSG shift points are more aggressive.
Dynamic Light Assist. This uses a camera on the windshield to analyze information on other road users and the street lighting in order to automatically mask the headlight main beams at speeds of more than 37 mph (60 km/h). The system allows the main beams to be left on continuously without dazzling oncoming traffic because a mask can partially dip the main-beam headlights. The headlights also swivel by up to 15 degrees while cornering and the left and right units have independent control. Light Assist.
For GTDs that aren’t fitted with Bi-Xenon headlights and the Adaptive Front- lighting System, Light Assist automatically switches on the main-beam headlights. The system detects vehicles travelling ahead and oncoming traffic, and automatically dips the headlights.
Road sign recognition. On GTDs equipped with a navigation system, this shows traffic signs on the display. If the system detects any speed limit or “No overtaking” signs via the windshield-mounted camera, up to three will get shown on the instrument cluster in front of the driver and on the navigation system display.
Park Assist. The latest version of the parking assistance system now facilitates both parallel and perpendicular parking. In addition, Park Assist 2.0 is also equipped with a parking space exit function. The system can be activated at speeds of up to 27 mph (43 mph) by pressing a button on the center console. Using the indicators, the driver selects the side on which the car is to be parked and if Park Assist detects a large enough parking space—16 inches, front and rear, is sufficient—the assisted parking can begin. All the driver has to do is put the vehicle into reverse and operate the accelerator and brake, as the car takes care of the steering.
Initial driving impressions
Volkswagen introduced the first version of the GTD in 1982—essentially a GTI (Golf’s gasoline-engined performance model) with Volkswagen’s then 70-hp 1.6-liter turbo-diesel engine. It’s hallmark, like that of the GTI, has been performance and handling. The new GTD extends and enhances that legacy extremely well—in addition to providing the benefit of much lower fuel consumption. With a tank capacity of 50 liters (13.2 gallons US), the GTD has a theoretical driving range of up to 1,190 km (739 miles).
Volkswagen hosted a US media drive from Berlin to Wolfsburg using the European spec GTD in Germany in June, following on the heels of an international media drive event.
Green Car Congress drove a GTD equipped with the Sport and Sound package and the six-speed manual on the several hour route. The GTD was well-behaved in Berlin traffic; the shifting is smooth, the interior content more than ample, the stop/start system quick to shut off and as quick to restart, without inconveniencing the driver.
(The close lateral proximity of cars in other lanes had the assistance system thinking we were going to park a time or two, which was mildly distracting as guides appeared on the HMI screen. But that’s probably more due to driver error.)
For a diesel, the GTD was quieter in town (inside the car) than expected. The restart after a stop/start event was quite audible as a combustion engine restart, but without the clatter that some might expect—despite optimization of the combustion—from a diesel.
That sound experience is partly due to the Actor function of the Sport & Sound package. The Actor was exclusively developed for the new Golf GTD. Depending on the engine revs and the selected driving profile, a sound system generates a more comfort-oriented sound (Normal and Eco modes) or a more powerful and full-bodied timbre (Sport mode). The engine sound is experienced in the interior as real sound generated from the outside via the exhaust system.
The faster the GTD drives, the lower the sound is, so as not to affect comfort on long distance journeys. In other words, inside the cabin, it doesn’t sound at all like a diesel. The Actor functions extremely well; unfortunately, we didn’t have a non-Sport and Sound package experience to be able to compare.
Where the GTD truly excels is on the highway. Acceleration and power feels effortless; even at the high end of the supported speed range, the engine felt as if it still had more to give. Overtaking was never a problem. With the optimized chassis and suspension, as well as the assistance systems, handling—again, even at the higher speeds—was solid.
Overall, the GTD was a delight to drive—especially on the highway and on the mountain roads. The car offers excellent range, low fuel consumption and very pleasing driving dynamics. The GTD would be a good choice for a road-tripping, highway commuter car with sprightly handling and performance, and is endowed with an array of advanced driver assistance functions.
(Volkswagen hosted Green Car Congress at the media drive.)