Get a Grip: SVT Mustang Cobra Traction Control System
11 December 1998
Get a Grip: SVT Mustang Cobra Traction Control System
DEARBORN, Mich., Dec. 11 -- The development of all-speed
Traction Control System (TCS) started with Ford customers who said
they were interested in a feature that would enhance traction and vehicle
stability in the rain and snow. Research disclosed that 57 percent of all
Mustang V-8 owners (and a remarkable 74 percent of V-6 owners) and potential
buyers would purchase a traction control system if available on the Mustang.
The challenge facing Team Mustang and development partner Bosch was to create
a system that not only satisfied these basic needs, but one that didn't
alienate loyal, performance-oriented Cobra owners who occasionally like to
engage in high-energy driving.
The primary goal: reduce the demands placed on the driver by maintaining
vehicle stability and steering response during rapid acceleration. To
accomplish this, Team Mustang's system had to be capable of inhibiting
wheelspin during initial or underway acceleration in a variety of conditions,
including driving on a road slick with rain or snow on one or both sides;
emerging from icy parking lots or highway shoulders; and acceleration during
cornering or lane changes.
The Team developed a number of tests to simulate these conditions. The
low-friction acceleration test was when all four tires were on a slick
surface, such as an icy road. The split-friction test placed only one drive
wheel on a slick surface and the other on a dry surface. In the low-friction
lane change maneuver, engineers simulated an accelerated lane change on a
slick surface. Finally, the asphalt-to-gravel cornering test combined
acceleration and cornering on a low friction surface.
After considerable testing, the Team developed a hybrid traction control
system for the Mustang that combines brake and engine management to control
wheelspin. When any of the four ABS/traction control sensors detect that a
drive wheel is spinning at a rate higher than its counterpart, ignition spark
is retarded and the fuel/air ratio is modulated to attenuate torque delivered
to the slipping tire. If the condition persists, cylinder cut-off occurs,
brakes are applied to the wheel with low friction, and power is transferred to
the other drive wheel. The driver is informed of TCS events via an indicator
light in the instrument cluster.
TCS may not significantly improve traction when both wheels are on a
slippery surface, but it optimizes the use of available traction. The benefit
under this condition is improved vehicle steerability and stability provided
by controlling excess wheel slip.
The system is very sensitive to driving conditions -- it employs the
difference in slip rates at the wheels to distinguish between cornering and
acceleration slippage -- and it is extremely fast acting. In computer-speak,
it has a "64-millisecond update capability." With TCS, the drive wheels are
searching for optimum traction several times per second and adjustments are
implemented accordingly.
The Cobra TCS was also designed to meet the performance needs of more
aggressive drivers, permitting some wheelspin when the system detects that
wheelspin is the driver's desire. Not only did Team Mustang provide a driver-
selectable On/Off switch for the TCS, but perhaps its most clever aspect: the
Power Start feature.
Power Start senses when the driver is accelerating hard and goes into a
performance programming mode that enables optimum wheelspin from a standing
start on dry pavement. As long as the Cobra accelerates forward, the Power
Start feature stays engaged and the Mustang responds as it would without
traction control. When the system detects that the car is turning away from
the straight, however, TCS is re-engaged.
For repeated hard acceleration, Team Mustang recommends utilizing the Off
switch on the console, though at no time can the ABS be switched off. The TCS
defaults to On mode when the engine is started.
This capability was specifically designed for the Mustang -- whose
flagship is the SVT Mustang Cobra. It provides the correct blend of traction
and control that customers wanted, plus the high-performance operation Cobra
drivers are unwilling to give up.
The sophisticated All-Speed Traction Control System is standard equipment
on all 1999 Ford SVT Mustang Cobras.