Acura Introduces Super Handling All-Wheel Drive

Motor, Nov 2004 by Nash, Tom

The all-new 2005 Acura RL features a revolutionary Super Handling All-Wheel Drive, or SH-AWD. It's the first all-wheel-drive platform that distributes the optimum amount of torque not only between the front and rear wheels but also between the left and right rear wheels. The result, says Acura, is cornering performance that provides neutral steering and excellent vehicle stability.

By monitoring driver input and driving conditions, the SH-AWD system determines the optimum front/rear and lateral (left/right) torque distribution. This information is then conveyed to the rear differential, where direct electro-magnetic clutches continuously vary the front-to-rear torque by up to 70% in either direction. Rear torque can also be apportioned between tire left and right rear tires by up to 100% on either side.

The SH-AWD system is composed of an ECU, sensors that detect steering angle, lateral g-force and other vehicle information, and a rear differential. The direct electromagnetic clutches inside the rear differential are able to maintain precise control over the multiplate clutches.

The SH-AWD system uses torque not only for propulsion, but also to increase cornering precision and enhance vehicle maneuverability while helping to virtually eliminate understeer and oversteer. During cornering, the speed of the outside rear wheel is greater than the average of both front wheels. This prevents the efficient transfer of torque to the outside rear wheel in a typical AWD system. To counteract this, the SH-AWD systems rear differential has a built-in acceleration device that can overdrive the outside rear wheel. This device uses a planetary gear to speed up the outside rear wheel's rotation relative to the front wheels. The result is a significant enhancement in vehicle maneuverability during cornering.