Super Handling-All wheel Drive also known as SH-AWD is a torque vectoring and
intelligent all wheel drive system developed by Honda that operates differently
from conventional all wheel drive systems. Sh-awd differs from other systems in two ways.
Super handling all wheel drive, although an all wheel drive system, the engine and
transmission is mounted up tranversely which is similar to a front wheel drive to send power
to the front wheels. A torque transfer unit is attached to the front transaxle which spins to send power to a rear
differential to drive the rear wheels instead of a traditional driveshaft.
- It differs in the method used to distribute the power to the wheels that need it (all wheel drive).
- It uses a different method to gain better on road control during cornering and to reduce skidding (torque vectoring).
Sh-awd improves cornering as it is an all wheel drive system that handles traction control
and handling in a unique way. Sh-awd distributes torque between the front and rear wheels and regulates
the amount of torque sent to the left and right rear wheels during cornering.
A Honda Legend/Acura RL with SH-AWD
Many all wheel systems have a fixed amount of torque that is sent to the front and rear wheels but super handling all
wheel drive can send 30% of the torque to the front wheels and 70% to the rear wheels or vice versa depending on the driving
When the car is cornering the rear wheels should have 70% of the overall torque depending on the degree of the turn.
Out of the 70% that is sent to rear wheels the outer rear wheel will receive more torque, up to the full 70% to propel the car
into the corner more precisely at a higher speed.
An example would be cornering to the left at 50mph. If the sensors detect the corner is too much for the vehicle other systems may
reduce power or apply brakes to the left wheels which are the inside wheels. This system will
send more power to the rear right wheel which is the outside wheel to propel the vehicle into the corner without the need to reduce the
power or speed.
The way sh-awd distributes the torque between the left and right wheels is by using a central hypoid gear in the rear differential
and two electromagnetic clutches, one on each side of the hypoid gear. As the car corners in the same example the right side will receive
more force as more weight will be thrown to the right. These forces affect the gaps around the electromagnetic clutches and this is used
to measure and distribute the torque to the appropriate rear wheel. The front wheels usually split the torque given to them 50/50.
SH-AWD can switch the torque from one wheel to another within several hundred milliseconds as the driving situation demands. BMW and
Audi have similar systems in Dynamic Performance Control and Audi Torque Vectoring respectively. I'm not going to say which is better or the
best system but BMW and Audi have a traditional approach for example they have a driveshaft to transfer the torque to the rear wheels and
that makes Super Handling All Wheel Drive different.