SH-AWD

SH-AWD, an acronym for Super Handling All Wheel Drive, is an all-wheel drive platform designed and engineered by Honda Motor Company. The company describes it as "A world’s first, the SH-AWD system combines front-rear torque distribution control with independently regulated torque distribution to the left and right rear wheels to freely distribute the optimum amount of torque to all four wheels in accordance with driving conditions."fact|date=January 2008

It was first developed for the 1997 Honda Prelude Type SH, albeit in a front-wheel drive form. Another variant of the system is also being featured on the 2007 Acura RDX and Acura MDX SUVs.

It essentially is a set of clutch packs in a T-shaped differential at the rear of the vehicle. There is no center differential. Rather the vehicles have transverse mounted engines with power take-off units going to the T-shaped rear differential/clutch packs. The three clutch packs can engage for the right rear wheel, the left rear wheel, or near the base of the T. With the Acura RL sedan, the system sends 70% of power to the front wheels and 30% to the rear under normal conditions but these ratios can reverse according if needed. The system can work because the clutches can slip under circumstances where the vehicle is turning, thus allowing the rear and front wheels to turn at different rates around a curve. SH-AWD in the Acura RL also features an "acceleration device" just ahead of the rear differential which, through the use of a planetary gear set, can overdrive the rear axles by as much as five percent. This is done only when cornering.

SH-AWD in the Acura RDX and Acura MDX use a default power split of 90% to the front and 10% to the rear. Like the unit in the RL, both can power the rear wheels with up to 70% of the engine torque. With this variant of SH-AWD, there is no acceleration device. Instead, the rear differential is constantly overdriven by 1.7 percent. During straight line performance, that difference is scrubbed off by the clutch packs. When cornering, the difference is used to overdrive the outside rear wheel.

The power split under straight-line, high-speed acceleration varies from vehicle to vehicle. It approximates the weight distribution for each.

ee also

* All-Trac - a four wheel drive system from Toyota
* ATTESA - a four wheel drive system from Nissan

References

* http://www.acura.com/index.aspx?initPath=RDX_Learn_FeaturesOptions_Performance_SHAWD_SHAWDOverview