|The 2013 Jetta Hybrid. Click to enlarge.|
Volkswagen is holding media drive events this week for the sporty new 2013 Jetta Turbo Hybrid (earlier post), which features the second version of a Volkswagen gasoline-electric hybrid drive system: a 1.4L turbocharged EA211 engine; a hybrid module featuring a 20 kW electric motor and a disengagement clutch; a 7-speed DSG transmission; and a 1.1 kWh Li-ion battery pack.
Volkswagen, seeing the hybrid as complementary to the Jetta TDI diesel in attracting different, yet equally fuel-economy-conscious buyers, is initially targeting 5% of Jetta sales in the US for the new hybrid model. The company anticipates EPA-rated combined mileage of around 45 mpg US (5.2 l/100 km). The Jetta Hybrid can accelerate from 0-60 mph in 8.6 seconds, and has a top track speed of 125 mph (201 km/h), electronically governed in the US.
The Jetta Hybrid will allow VW to attract new customers who don’t consider TDI (diesel) as a legitimate rival to hybrids.—Rainer Michel, Volkswagen VP product marketing and strategy
|Jetta Hybrid powertrain. Click to enlarge.|
Volkswagen’s first gasoline-electric hybrid system—that for the Touareg Hybrid—combines a 3.3-liter supercharged V6 direct injection gasoline engine; a hybrid module integrating a 35 kW electric motor and disengagement clutch; an 8-speed automatic transmission; and a NiMH battery pack. (Earlier post.) The Jetta is the first Volkswagen hybrid with a Li-ion pack (cells from Sanyo).
The gasoline engine is one of Volkswagen’s latest EA211 series of small engines. This features many improvements over the previous EA111 generation, including lightweight aluminum construction, an integrated (into the head) exhaust manifold, and a toothed-belt drive for its double overhead camshaft valvetrain that incorporates variable intake timing. The only aspect to be carried over from its predecessor is the 82 mm cylinder spacing. The cylinder bore was decreased by 2 mm (to 74.5mm) while the stroke was increased to 80mm, a change which not only helps compactness, but also increases torque and presents a good basis canvas for adding boost (turbocharging or supercharging).
The 1.4-liter TSI engine in the Jetta Hybrid features a 10.5:1 compression ratio, direct fuel injection, and turbocharging to produce 150 hp (112 kW) at 5000 rpm. This engine’s turbocharging system offers solid boost response due to its intake manifold, which enables the use of a small, single-scroll compressor. The intercooler is integrated directly into the injection-molded induction pipe. This design generates maximum torque of 184 lb-ft (249 N·m) at 1600 rpm.
|Hybrid module. Click to enlarge.|
The integrated hybrid module unit with its water-cooled 20 kW motor can add a constant 114 lb-ft (155 N·m ) of torque. Combined, the system puts out 170 hp (127 kW) at 5000 rpm and 184 lb-ft (249 N·m) of torque at a low 1000 rpm, giving the car smooth acceleration. (The maximum torque is limited by the transmission.)
The high-voltage battery placed above the rear axle (encroaching into the trunk space) powers the Jetta Hybrid’s electric motor. This 60-cell system produces a total voltage of 220 V, rated energy of 1.1 kWh, and pulse power of 32 kW.
An industry first, the Jetta Hybrid uses a seven-speed, DSG dual-clutch automatic gearbox. This DQ200 transmission is the most efficient of Volkswagen’s DSG units and employs a dry-clutch design, as opposed to the wet-clutch arrangement seen in many other Volkswagen products. This unit can be operated as a pure automatic (“D” mode) or shifted manually. There is also a sport setting (“S” mode).
Due to the powertrain and features such as a newly designed exhaust system, an acoustic windshield, and thicker front side windows, the Jetta Hybrid is the quietest car Volkswagen has offered in the compact sedan class.
The Jetta Hybrid starts up as an electric vehicle and will remain like this up to speeds of 37 mph (60 km/h), dependent on how hard the driver wants to accelerate, on the topography, and on the state of charge of the battery. In this mode, the gasoline engine is stopped and is actually entirely disconnected from the drivetrain to eliminate any loss in efficiency through parasitic drag. Even though the￼engine isn’t working, the HVAC and electrical components like the audio system continue to operate. Although not designed for long-range, all-electric driving, the car can remain in this mode for more than a mile, given the appropriate conditions.
If the driver selects the “E-Mode” button to the right of the shift lever, the zero-emissions, electric mode is maintained up to 44 mph (71 km/h) and allows for more aggressive gas pedal inputs. This mode requires adequate battery charge and temperature: if the battery is depleted, the system will reactivate once it has regenerated enough power.
Above 37 mph (44 mph in E-Mode), when the battery level is low or there’s a demand for additional power, the Jetta Hybrid taps into the turbocharged engine. Once the driver has depressed the gas pedal the required amount, the clutch immediately and seamlessly closes, thus starting the gasoline engine. Once operating, the engine delivers more power than is needed in order to charge the battery pack.
If maximum acceleration is needed (either through kickdown in “D”, or with the shift lever in “S” or in the manual gate), the system will begin “Boosting”. In this mode, the electric motor works in conjunction with the gasoline engine, assisting it to achieve the total system output of 170 hp. During these periods of “active boost” assistance, the primary role of the electric motor is to ￼increase the powertrain’s output.
There is also a “passive boost” state, in which the electric unit takes over accessory power, leaving the gasoline engine to focus on sending all of its power to the transmission. (Theoretically, this is the same as eliminating the parasitic drag created by a conventional car’s alternator.)
While the gasoline engine charges the battery during non-boost states, this requires energy and thus, fuel (albeit a minimal amount). The only truly “free” way of sending charge back to the battery is through regenerative braking. This process occurs whenever the driver applies the brakes, causing the Jetta Hybrid to convert the kinetic energy (in the form of heat) generated by braking into electricity in the battery. The Jetta Hybrid increases the amount of regeneration by decoupling the engine from the drivetrain, reducing drag caused by engine braking and also increasing the amount of retardation needed (and thus heat).
The engine is also shut off and is decoupled from the driveline to eliminate drag caused by the engine’s torque at higher speed—up to 84 mph—when the driver releases the gas pedal. This helps to save fuel when, for instance, the car is going down a gentle slope or is coasting to a halt.
The Jetta Hybrid adds a number of key features that help maximize aerodynamic efficiency and minimize road resistance. A Hybrid-specific air intake provides a flush seal and controls the flow of cooling air passing through the engine compartment. A custom trunklid spoiler and front airdam have been designed exclusively for the Jetta Hybrid’s aerodynamic needs, as have the extended side skirts. The differences carry over to the car’s underbody, where additional trim panels and end plates serve to guide the back to a diffuser at the rear, which helps reduce turbulence and control the flow and separation of passing air. The result of these changes is a Coefficient of Drag (Cd) of 0.28, compared to a Cd of 0.30 for the conventional Jetta.
The Jetta Hybrid’s advanced powertrain is highlighted by a set of displays inside the car. Taking the place of a traditional tachometer is the Jetta Hybrid’s “Power Meter”—a rethink of traditional instrumentation. The dial starts at “OFF,” (essentially zero rpm), which is followed by a green “regeneration” section (active during braking) before reaching the baseline drive-ready state, which is represented with a “0.” This begins a blue section of the dial that signifies the most efficient driving style, alternating between electric and gasoline engine power; the half-blue section that follows it indicates times when only the gasoline engine provides power while charging the battery. At the dial’s “6” position, the blue markings are gone and the vehicle is utilizing the gasoline engine’s power without charging the battery. The final step is the boost mode at “10”: marked like a traditional redline, this demarcates the point when the electric motor and gasoline engine are working together to achieve full system output.
Situated to the right of the Power Meter and between the two gauges is the car’s standard Multi-Function Instrument, which shows ambient temperature, gear selection, the trip computer, a second audio display, and driver settings. In the Jetta Hybrid, this screen also presents the car’s drive state and the “ePower meter,” which includes the level of battery charge and the available amount of electric driving (“E-Max”).
On the SE model and above (there are four trim levels for the hybrid, earlier post), the radio/navigation system’s touchscreen in the center console also doubles as a visualization of the powertrain’s operation. One example of this is the emissions statistics screen, which displays a bar graph showing the minute-by-minute percentage of zero-emissions driving in relative percentages (the previous 30 minutes are shown). The display also shows a diagram of the car and its underlying powertrain, with orange and blue areas (gasoline and electricity, respectively) representing exactly where power is coming and going at any given time and in any given drive mode. The display also includes the monitor for the rearview camera on the SEL Premium model.
The Jetta Hybrid features a suspension designed for lively handling, as well as comfort and stability. The front end employs damper struts with lower control arms and an anti-roll bar. At the rear, the car uses a multi-link, independent layout featuring gas-pressurized dampers and separate coil springs. Combined with Volkswagen’s latest electric power steering system, the Jetta Hybrid offers precise, sporty road manners without sacrificing smoothness or comfort.
Available exclusively through special order, the Jetta Hybrid begins at $24,995.
Driving impressions. Green Car Congress attended the media drive events held in New Mexico. With the limited exposure of such an event, the Jetta Hybrid showed itself to be smooth and sporty, and handled extremely well on the roads between Santa Fe and Taos. The transitions between engine and electric motor were almost unnoticeable, and the hybrid showed plenty of zip for passing—even on a long upslope. Brake regeneration was equally smooth—and perhaps could even be a little more aggressive, especially in E-mode.