Super Handling-All Wheel Drive (SH-AWD) is a full-time, fully automatic, all-wheel drive traction and handling system, which combines front-rear torque distribution control with independently regulated torque distribution to the left and right rear wheels.
This action pushes the rear around the corner, reducing understeer and keeping the car balanced and controlled.
The SH-AWD all-wheel-drive system was lauded by Popular Science as one of the best automotive innovations of 2004,[citation needed] and as part of an already tech-filled vehicle helped to earn the 2005 "Tech car of the year" from CNET.
The VTM-4 system consisted of a pair of computer-controlled wet clutches in the rear axle that worked in concert with the front wheels regardless of road conditions.
In the dry, this served to reduce front-wheel drive torque steer, and provide more front tire adhesion for cornering.
As speeds increased, the power to the rear wheel would decrease, and by 18 mph, the system would revert to front-wheel drive.
[11] SH-AWD combined both the automatic all-wheel drive VTM-4 system capability with the "super handling" torque shifting ability of ATTS on the rear axles.
In the North American market, Honda introduced the original SH-AWD system in late 2004 with the second generation 2005 Acura RL.
This improved version provided earlier SH-AWD intervention (first gear vs second),[14] and more precise use of the rear differential electromagnetic clutch system.
As of 2010, the Acura RL remains the only SH-AWD configuration with the variable speed rear differential acceleration device.
In December 2010, the 2011 Acura RL was announced[22] with a second Mid Model Change, featuring, among other things, a six-speed automatic transmission.
The V-6 would be mated to a 30 kW electric motor which could operate independently of the V-6, unlike earlier mild hybrid Honda IMA configurations.
In addition, each rear wheel would have a 20 kW electric motor that would operate independently, varying torque as conditions demand.
A prototype of this system was shown in a test mule using an 8th generation North American version of the Honda Accord.
The Acura RL is designed with a third planetary gear set and clutch pack that are packaged into a so-called "Acceleration Device", which is bolted in front of the rear differential unit.
[26] As of early 2010, SH-AWD has been implemented by Acura in two functionally similar, but mechanically different configurations, with and without Acceleration Device.
In addition, in cornering situations, dependent on the specific vehicle balance and dynamics, the rearward power transfer ratios in the RDX and MDX differ greatly from the RL and TL sedans.
For example, when it comes to torque distribution, SH-AWD is front-biased (with the exception of the performance oriented UB5 TLX Type S) but Audi's Quattro is rear-biased.
While the rear differential also acts like a limited slip differential in spirited driving, SH-AWD is deeply integrated into the Honda Vehicle Stability Assist (VSA) system and various onboard sensors which helps to keep the car under control in a variety of situations.
[31] The first generation Acura RDX is a small crossover utility vehicle, and features a simpler implementation of SH-AWD than that found in the RL.
The second generation Acura MDX, introduced in late 2006 as a 2007 model, uses a simpler implementation of SH-AWD than that found in the RL, the main difference is that unlike the RL 70% front/30% rear torque distribution, the MDX offers the opposite, having a 30% front/70% rear torque distribution.
[34] The first generation Acura ZDX was announced on April 8, 2009 at the New York Auto Show as a 2010 model, slated for introduction in late fall 2009[35] as an all new prototype concept car, billed as a luxury four-door sports coupe.
[36] The car is powered by an all-aluminum 3.7L 300 horsepower, 270 lbs-ft torque VTEC V-6, mated to an all-new 6-speed automatic transmission with Sequential SportShift and Super Handling All-Wheel Drive.