| July 5, 2011
Drivetrain
Source: Audi of America
The engines in the Audi Q3 work together with a variety of different transmissions. The 2.0 TFSI with 125 kW (170 hp) and the 2.0 TDI with 103 kW (140 hp) to appear somewhat later are mated to a manual six-speed gearbox. Models with the two top-of-the-line engines come standard with a seven-speed S tronic. All of the transmissions feature hydraulic bearings; this minimizes the propagation of vibrations and noise. The manual gearbox has a particularly lightweight magnesium casing. It features short, precise throws and is highly efficient.
With both transmissions, the short-ratio lower gears provide for powerful acceleration. The long ratios of the highest gears reduce engine speed and with it fuel consumption.
High-performance: the seven-speed S tronic
The seven-speed S tronic is a versatile transmission. Drivers can let it shift automatically or change gears themselves using the selector lever or the optional paddles on the steering wheel. Two driving modes are available: In D mode, the engine runs as often as possible at low revs; in S mode, the driving style is sporty and the revs are higher.
The seven-speed S tronic transfers the engine’s power via three shafts – one drive shaft and two output shafts. This layout enables a short design, which is necessary for pairing it with the transverse four-cylinder engines.
Like all dual-clutch transmissions from Audi, the seven-speed S tronic comprises two transmission structures and integrates two multi-plate clutches. The large K1 clutch located on the outside conducts the engine torque via a solid shaft to the gear wheels for the odd gears 1, 3, 5 and 7. A hollow shaft rotates around the solid shaft. It is connected to the second, smaller K2 clutch, which is located inside its larger sibling, and which controls the gear wheels for the gears 2, 4 and 6, as well as reverse gear.
Both transmission structures are continuously active, but only one is connected to the engine at any one time. For example, when the driver accelerates in third gear, the fourth gear is already engaged in the second transmission structure. Shifts are performed by switching the clutches. Shifting gears takes only a few hundredths of a second and is completed with almost no interruption of traction. It is so dynamic, fluid and smooth that the driver hardly notices it.
The mechatronics module on the outside of the seven-speed S tronic is a compact and robust block comprising the control unit and the control and positioning valves. Among other things, it varies the speed of gear changes and precisely regulates the force required.
The management system for the multi-plate clutches is extremely precise. The transmission is responsive even in stop-and-go traffic and while maneuvering.
The oil in the seven-speed S tronic cools and lubricates the gears and the clutches. It also drives many of the components of the mechatronics module. A positioning valve regulates the flow of oil based on demand, keeping it as low as possible. The high-tech transmission can withstand heavy loads. A carbon coating makes the synchro rings extremely durable; gears one through three and the reverse gear are shifted via a triple-cone synchronizer.
One innovation featured in the S tronic is the free-wheel function. If the driver has selected “Efficiency” mode in the optional Audi drive select system, the clutch disengages when coasting, regardless of which gear is currently engaged. The sporty SUV free-wheels, which further reduces its fuel consumption.
Sportiness and stability: the drivetrain
The Audi Q3 2.0 TDI with 103 kW (140 hp), to follow somewhat later, drives the front wheels. All other engines are paired with quattro permanent all-wheel drive. Its greatest strength lies in the enhanced slip-free acceleration, road dynamics, safety and directional stability that it delivers. The compact SUV is dynamic and stable, even in wet and slippery conditions. It safely delivers its power to the road when exiting corners.
The heart of the quattro drive system in the Audi Q3 is an electronically controlled, hydraulically actuated multi-plate clutch. In the interest of better axle load distribution, it is located on the end of the prop shaft, in front of the rear axle differential. Inside the clutch is a package of plates that rotate in an oil bath. The metal friction rings are arranged behind one another in pairs – one ring of each pair is rigidly meshed with the housing, which rotates with the prop shaft; the other ring is meshed with the output shaft to the rear axle differential.
During normal driving, the clutch sends most of the engine’s power to the front wheels. If traction decreases there, the clutch can transfer torque steplessly to the rear axle in just a few milliseconds by forcing the packages of plates together via controlled action.
A pressure reservoir helps the electric reciprocating piston pump to develop the necessary oil pressure, which can reach over 100 bar. If a wheel on one of the axles should slip, it is braked by the electronic differential lock (EDL).
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