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'Q2' self-locking differential

The system is based on a Torsen mechanical-type limited-slip differential. The job of this differential is to divide the torque between the (front) driving wheels depending on the grip conditions. Combined with the exclusive front wishbone suspension, the system ensures particularly effective dynamic control of the vehicle. In addition to the general benefits of this type of architecture (weight, space, etc.), in limit conditions the understeering behaviour of the front-wheel drive system enables the driver to act more intuitively: this gives the impression that front-wheel drive is 'more reliable' than rear-wheel drive.

To get a better understanding of the behaviour of Alfa's new 'Q2' system, we have two examples: car on a bend (case 1) and on a surface with poor grip (case 2).

CASE 1: CAR ON BEND

When taking a bend in poor grip conditions (in the rain or snow, or on muddy roads, etc.) or with a sporty drive, it often happens that the car's inside wheel loses grip. When the torque transmitted to the inside wheel is reduced, because of the lightening of the suspension due to lateral load transfer, a traditional differential (which delivers the same torque value to both wheels) transfers an equivalent torque value to the outside wheel, which is not enough for adequate traction.

In this situation, there can be two different vehicle responses, depending on the car's equipment. On a model without ASR - VDC, the perceived result is slippage of the inside wheel, loss of vehicle control (strong understeering) and a lack of acceleration on exiting the bend. If the car is fitted with ASR - VDC, on the other hand, the intervention of these drive assistance systems reduces engine power by closing the accelerator throttle and activating the braking system, making it impossible to use the accelerator properly and giving an unpleasant sensation of a drop in power.

In both cases, the result is that on exiting the bend one has the impression of having come to a standstill.

What happens with the 'Q2' system?

The moment the inside wheel begins to lose grip, torque is partially transferred to the outside wheel, thus ensuring less understeering, greater stability, and greater speed on the bend.

This improved mechanical performance provided by the 'Q2' transmission delays the intervention of the vehicle's control systems, thus ensuring better traction on exiting the bend, all of which translates as more driving pleasure and total control of the vehicle.

CASE 2: SURFACE WITH POOR GRIP

When driving on surfaces with poor grip, it often happens that the two driving wheels experience different grip conditions. For example, when driving on a wet or snow-covered road, the two wheels could find themselves turning in different conditions.

In these conditions, an abrupt start or rapid acceleration could lead to the wheel under critical grip conditions slipping, with consequent powerful pulls on the steering wheel, insufficient power and the need to make constant steering wheel corrections to maintain the car's trajectory.

What happens with the 'Q2' system?

The negative effects are countered by the gradual transfer of torque to the wheel with better grip, making it easier to make a hill start or making travelling on a road surface with changeable conditions safer and more comfortable.