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Technology: Alfa Romeo’s Q4 All-Wheel Drive System:

What Goes Into Alfa Romeo's AWD System...

A mountain hairpin, a gravel road, a snowy surface, cornering on wet tarmac, with Alfa Romeo’s Q4 all-wheel drive (AWD) system, driving has never been better.

Q4 ensures all the advantages of AWD and, at the same time, without compromising the driving fun of a rear wheel driven vehicle and its unique thrills and superior driving dynamics.

At the heart of the Q4 system is the Active Transfer Case (ATC) which monitors grip conditions and driver inputs in real-time to ensure the best performance and, whenever needed, can transfer up to 50% of the engine torque to the front wheels via an extremely compact, lightweight front differential.

Combine maximum safety with maximum performance in every driving situation, from the racetrack to snowy roads: these ambitious goals inspired the development of a proactive on-demand AWD system designed to challenging specifications, and whose control strategies, internally implemented by the Alfa Romeo team, enhance the vehicle’s sporty attitude and driving pleasure.

2019 Alfa Romeo Stelvio Quadrifoglio. (Alfa Romeo).

Mainstream solutions in the segment are primarily based on permanent AWD systems. These are less dynamic, and are biased to a fixed torque distribution value (e.g., 70% Rear – 30% Front in normal conditions) and, once one of the axles starts slipping, the speed difference between the tires leads to a different torque distribution value between front and rear axles (e.g., 50% Rear – 50% Front) purely achieved by mechanical means.

Alfa Romeo’s Q4 system instead allows the vehicle to travel as a pure rear wheel drive and, if tire grip  is approaching its traction limit, or in case of high dynamic maneuvers, it can instantly deliver up to 50% of the engine torque to the front thus preventing wheel slip and ensuring maximum vehicle performance and driving effectiveness.

Torque Vectoring Optimized Cornering. (Alfa Romeo).

Torque distribution is then constantly modulated with high dynamic and extreme precision according to the effective traction conditions and driver commands: this translates into best in class vehicle control concerning traction and directional stability when cornering.

Alfas Q4 system ensures that traction is used to max out performance in any condition, increasing vehicle handling, and, if needed in extreme circumstances, stabilizing it before the intervention of the brake electronic stability control without impairing performance.

Between the “On Demand” AWD systems, Q4 represents a generational leap: enthusiasts have always known that traditional AWD vehicles tend to understeer. But with Q4, Alfa Romeo’s sporting heart beats at a different rhythm in every configuration of the DNA selector, creating the maximum emotional involvement in the Dynamic setting. This system was designed to give you the pure driving feeling of rear wheel drive with maximum safety guaranteed by having traction available on all the four wheels.

Q4 Integrated Actuation Chain Driven Active Transfer Case. (Alfa Romeo).

To further enhance vehicle dynamics and handling Alfa Romeo has opted for a unique feature within its Q4 System: different gear ratios between the front and rear axles. Even on variants without staggered tires, this allows the vehicle to come out of a corner faster thanks to early vehicle stabilization. This design enables you to accelerate earlier out of a turn than an AWD vehicle without this feature, meaning using the same gear ratios in front and rear axles.

In order to be able to offer this level of performance, the entire system has been designed with challenging, innovative specifications: the active transfer case (ATC) was designed to rapidly and accurately adjust the amount of torque sent to the front axle, instantly modifying it according to available traction, the driver’s requests and to the vehicle’s dynamic behavior.

Reaction times are a reference in its class: the system can send almost 1000Nm to the front differential pinion in under 150 milliseconds, and decrease from 1100Nm to 100Nm in barely 120 milliseconds.

Q4 can withstand intensive use, e.g., driving to the limit on a race track or on low grip surfaces, dissipating very high energy in the clutch assembly without adding external cooling systems. This design is unique in the market, able to guarantee extremely dynamic, long-term driving without overheating.

Q4 High-Efficiency Front Axle. (Alfa Romeo).

The Alfa Romeo Q4 active torque distribution system (Active Transfer Case or ATC) also has unrivalled input/output torque levels in its class, being capable of accepting up to 5000Nm input torque from the transmission and deliver (ratio 1:1) up to 1200Nm to the front axle pinion via chain transmission which ensures that ensures quiet, efficient reliable operation thanks to its pumpless design.

This peculiar clutch operation strategy, enabling pure RWD driving in normal conditions, allows for high-efficiency and reduced fuel consumption in comparison with other AWD solutions on the market.

Alfa Romeos Q4 front differential unit is extremely compact and lightweight. It is also very efficient thanks to specific design elements that have been designed to reduce drag losses to a minimum. The overall weight increase of the AWD System, including the front halfshafts, is less than 110lbs with oil, a fantastic feat in design.

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