One of the new technological features of the 2011 Mustang has gotten a bit over-shadowed by all the whooping and hollering about the return of the 400hp 5.0 V8, the 305hp standard V6 and now the all aluminium 5.4 litre 550hp GT-500 engine.
What lies beneath those great new power plants is a new Electronic Power Assisted Steering (EPAS) rack that amplifies the new power and efficiency of those engines. Additionally, this change represents a first use of this new technology in a muscle car, let alone the Mustang.
The main benefits and reasoning behind moving to electric assist is the elimination of the weight, drag, and complexity of the engine driven hydraulic pump. Not only has horsepower been freed up, more efficiency gained, the power steering as a system been reduced to a single self contained component. The system saves approximately 3 hp and increases gas mileage by about 4% claims the manufacturer of the unit, Nexteer.
The best part of the new system for driving enthusiasts is the inherent handling precision improvements it brings. Hydraulic power steering systems by design place a cushion of hydraulic fluid between the actual steering gear and steering shaft. When you turn left or right you are getting a little bit of slop, a bit of lag as that hydraulic fluid is moving in and out of an actuator valve that controls steering boost. Though minute in the grand scheme of things, this removes a lot of steering feel and that direct gear to gear connection that allows a driver to pick up on messages the tires are sending up the line.
In the case of Mustang’s electric power steering assist system, the steering shaft is solidly connected to the pinion gear that acts left and right on the rack. A non-touching sensor resides at the base of the steering shaft that picks up the driver’s inputs and passes that information along to the electronic control unit. Power assist is given through a separate pinion gear located on the opposite side. So there is nothing coming between you and the feel of the road.
Because the system is controlled electronically, software can monitor various other conditions such as vehicle speed, steering angle, and traction conditions to give variable levels of assist. This means that Ford has been able to program the system to give more assist at a stop or at slow speed such as in a parking lot. Conversely, less assist is given at high speeds to give you a heavier steering feel for more control. In the presentation of the new 2011 Shelby GT-500, the SVT engineers stated that they spent a lot of engineering time programming the system to allow maximum road feel and handling characteristics.
Ford says that EPAS has made a dramatic contribution to the 2011 Mustang’s driving dynamics, delivering quicker on-centres steering response, increased effort at highway speeds and reduced effort required in low-speed parking manoeuvres. EPAS will have specific tuning for each Mustang model.
