Continental AG’s MKC1 brake-by-wire system makes its world debut in Alfa’s all-new Intelligent Braking System (IBS). Brembo brake calipers are still hydraulically operated rather than electro-mechanical but what’s changed is the front end. Instead of acting directly on a hydraulic master cylinder as usual, pressure on the brake pedal is transformed into hydraulic pressure by an electronic control module (ECU). One braking unit weighing 6kg replaces four weighing 10kg on a conventional system and takes up less space.
The driver gets a brake pedal feel that remains consistent and firm, however hot the brakes may get (so no spongy pedal on track). Standard calipers are aluminium four-piston on the front and cast-iron single piston on the rear. “The Quadrifoglio is designed to drive from home to work during the week and to go on track at the weekends,” says test co-ordinator Federico Langarelli Sellani, so rear calipers are also aluminium four-piston on those models. An optional four-wheel carboceramic (CCM) disc brake with sixpiston front calipers gives a generous weight saving of 5kg per wheel and colossal, inexhaustible braking performance.
3. Q4 on-demand all-wheel drive
Alfa Romeo teamed up with Magna Powertrain to design its own unique Q4 on-demand all-wheel-drive system, available only on the Stelvio in the UK. “The system is performance focused and normally delivers all the torque to the rear. This not only gives a rear-wheel-drive feel but is also fuel efficient,” says Q4 chief engineer Alessandro Avallone. At the heart of the system is an Active Transfer Case (ATC) housing a wet clutch pack to distribute torque to the front and rear axles. A compact front differential weighs only 11kg and the total weight of the system is less than 50kg.
An electronic brain, the Chassis Domain Control, measures the car’s yaw rate, wheel speeds, steering angle and throttle position. The clutch pack in the transfer case can react in less than 150 milliseconds to transfer up to 885lb ft torque to the front axle, the exact amount being continually varied “like a heartbeat”, says Avallone, to keep the car in balance.