Honda's Sci-Fi 4wd In The Acura Rl/legend Fast Cars - Now

Honda has come up with the most amazingincreases stability. SH-AWD also does that.
4-wheel-drive system, not for off-roaders but toMore power to outer rear wheel for better cornering
improve the handling and stability of fast cars. It isThe side-to-side variation in power is used to improve
being used first in the new Acura RL (Honda Legend).cornering power and stability. For example, when you
Why is it so advanced? This SH-AWD system hasaccelerate through a corner, extra power through the
the potential to increase cornering power andouter rear wheel counteracts understeer, letting the
cornering safety by leaps and bounds. It will be idealcar corner on rails. In fact, stability control systems
for supercars as well as luxury coupes.(Moreused on many cars now do this by reducing the
information about supercars at )amount of torque sent to the inner wheel – this
First, it allows the amount of power sent to the wheelsmeans that you actually corner slower than you could
to be varied from 30% front and 70% rear to 70%do. SH-AWD lets you corner faster.
front and 30% rear. True, some other systems getOn the over-run, you don't need that, and less power is
near that, but this allows the system to adjust itself tosent through the outer wheel for optimum stability. But
completely different conditions. On top of that, it canthat isn't enough because when a car corners, the
alter the torque from zero to 100% to the left or rightouter wheels have to travel further than the inner ones
rear wheel.– by 5-10% on very tight corners, so the outer
In other words, all the power can one to the rightwheel normally goes slower.
wheel one minute, and if necessary can be reversedHonda overcomes this with some gears in the back
so that all the power goes to the other wheel in anaxle gear set which actually drive the outer wheel
instant. This might be needed in slushy or snowyfaster when cornering! This improves maneuverability
conditions, where there was a patch of bare road forand cornering at low speeds.
a bit on one side offering good grip, but a bit later on aElectro-magnetic multi-plate clutches
bare patch on the other side.All this is accomplished by multi-plate clutches operated
In addition to those features, the outer rear wheel canelectro-magnetically – a world first – and
be speeded up so that it goes faster than the insidethe gear/clutch set used for acceleration. In fact, these
wheel! All done continuously depending on conditions. Agears also serve as the rear differential.
few years ago this would have considered desirable,An advantage of the electro-magnetic clutches is that
but science fiction.the electronic controller does not need to control a
More power to the rear wheel for accelerationhydraulic actuation system as used normally but an
Confused? Well, let's start with the front-to-rearelectric actuator – this reduces cost and weight.
power. When you accelerate, the weight of the car isIs this the best thing since sliced bread? For the person
thrown on to the back wheels by the force ofwho wants to have stability and control, and doesn't
acceleration, so you want more power to go to thewant to know what is happening to the car -yes. Such
back wheels – if it all goes to the front you geta system is bound to reduce the input the driver gets
wheelspin. When cornering, you generally want asfrom the road.
much or more power to the rear wheels. SH-AWDHe will be less aware of whether the surface is
does that.slippery, or whether the car is understeering more than
On the other hand, when you are cruising along, youusual because the SH-AWD system is correcting
want more power to the front wheels as thisthings all the time.