new RS Cosworth go back to 1988 when Ford established a new five year plan
for its motorsport activities. Central to this was World Championship rallying
in which the company was such a dominant force during the 1970s with the 
Mkl and Mk2 Escort - winning the Championship title in 1979. Formidable
competitor Through the 198O's, the Sierra RS Cosworth in both 2WD and 4x4
form has proved itself a formidable competitor in rally sport, but to compete
successfully in the 1990s at the highest level internationally, Ford Motorsport
recommended the development of an Escort-sized vehicle, where retaining
the power train and vehicle layout of the well-balanced Sierra Cosworth.
A concept car along these lines was built by Ford Motorsport at their Boreham
facility in the UK as a first step. Then, once programme approval had been
granted, development for production was taken over by SVE (Special Vehicle
Engineering), the department which has engineered all Ford's current generation
RS models. International rallying is run to Group A regulations which demand
a minimum 5,000 units to be built in one year before a car can be homologated
for competition use. (This figure reduces to 2500 units in 1993). Fully-fledged
production model However the RS Cosworth is no mere 'homologation special'.
From the start it was determined that the car would go in to full scale
production and that the road going version would have to meet the same
exacting standards as any other Ford model. SVE's task therefore. was to
turn that single prototype into a fully fledged production model and the
team has done this in just two years - astonishingly fast for what is in
most respects an all-new vehicle. The goal has been to produce not only
a potential rally winner but a road car that is reliable, refined and safe
as well as offering unmatched driver satisfaction. o Aerodynamcs-first
production car with positive downforce Aerodynamics are of the greatest
importance in both motorsport and for a high performance road car. SVE's
prime objective for the Escort RS Cosworth was to create a moderate level
of down force with emphasis being given to achieving a balance between
front and rear in order to improve grip and stability at high speed. However,
the spoilers that create this down force also increase drag so their size
and shape has to be chosen with care. An additional problem was posed by
the turbocharged engine which demands considerable cooling airflow - particularly
under competition conditions - and therefore also increases drag. Extensive
aerodynamic development These conflicting requirements were resolved during
some 200 hours detail development in Ford's own Cologne wind-tunnel. The
result is almost certainly a world first: a production car which generates
positive down force (or negative lift as it is sometimes known) at both
front and rear. In fact the RS Cosworth generates 45 Newtons of down force
at the nose and 190 Newtons at the rear at 180 km/h. The downforce is created
by a sophisticated arrangement of front and rear spoilers. At the front
is a conventional air dam type spoiler below and integral with the bumper.
In addition small spats run around the wheel arches at the edges of the
spoiler and an aerodynamic 'splitter' is fitted at its base. The spats
serve two roles: they give additional surface area to the front spoiler
to increase down force and also help deflect the airflow out and away from
the front wheels which reduces drag by approximately ten per cent. Aerodynamic
splitter The aerodynamic splitter - so called because its function is to
split the airflow above and below the car - is adjustable to three positions
the most forward of which is ideal for circuit use. The further forward
it is located the greater the down force (the figures above were recorded
with the splitter in its middle position) . At the rear, the large spoiler
at the top of the tailgate is an obvious source of down-thrust but the
smaller lower spoiler is equally important while the distance between the
two spoilers is crucial in determining down force and was fine-tuned at
some length in the wind tunnel. New production process The large rear spoiler
is manufactured by Resin Transfer Moulding (RTM) a process which is new
to Ford. Polyester mat is laid into mounds to form the top and bottom halves
of the spoiler: these are then closed around a centre core of polyurethane
foam and resin is injected around the core. The result is a tough and very
high quality glass reinforced plastic skin which is just 1.5 mm thick -
far thinner than could be obtained by traditional moulding methods and
a saving of around 50 per cent in weight compared with a conventional polyurethane
spoiler The aerodynamic drag effects of engine compartment cooling are
minimised by the use of a fully ducted cooling system. Air is channelled
through the radiator and around the engine escaping via specially shaped
bonnet louvres, further louvres at the rear edges of the front fenders
and from under the rear of the engine. An under-body tray below the power
unit manages this airflow and also reduces exterior noise levels. Despite
the additional spoilers and with the cooling drag penalty increased from
0.016 Cd on the standard car to 0.035 Cd, careful smoothing of the exterior
shape of the RS Cosworth has resulted in a final drag factor of 0.38 Cd.
which compares favorably with the standard Escort's 0.34 Cd. o Bodyshell
- exceptionally rigid and strong Overall some 50 per cent of the RS Cosworth's
body panels are new, while the remainder are derived from existing Escort
and Sierra components. The fuel tank is blow-moulded plastic which enables
the tank to be shaped to fill the space available. Its space-saving properties
have allowed a useful 65 litre capacity (compared with the standard Escort
capacity of 55 litres). it also features a latest technology in-tank fuel
pump. Body engineering was a joint exercise by SVE and by Karmann who are
manufacturing the vehicle. The front wings and rear quarters are wide to
accommodate an increased track and larger wheels. The rear body sides have
also been raised by some 30 mm to carry the lower spoiler at the correct
position. Overall the RS Cosworth is 175 mm longer 50 mm wide and runs
on a 26.5 mm longer wheelbase than the standard Escort. Finite element
analysis The RS Cosworth bodyshell has exceptional torsional stiffness
- 6 000 Newton meters of torque are needed to produce one degree twist
in the body. Extensive rig testing and finite element analysis studies
were carried out before the body's design was finalized to provide the
ideal characteristics, the only additional reinforcements needed to improve
rigidity were plates between the turret tops and the inner wings. o Engine
- latest version of turbocharged Cosworth power unit The 2.0 litre 16-valve
turbocharged YBT engine of the Cosworth is broadly similar to the YBG unit
of the Sierra RS Cosworth. However there have been a number of significant
changes made. Most important of these is the fitment of a new and larger
Garrett T3/T04B turbocharger with a two-stage inter cooler. The turbocharger
is a special hybrid unit which combines the turbine of the T3 with the
compressor of the larger T04B. It has been developed to provide good on-road
driveability together with the increased power potential needed for competition
usage. Two-stage intercooler The two-stage inter cooler is another feature
developed with motorsport in mind. The charge air passes through a water
cooled matrix before passing through a further air cooled matrix to give
substantial additional cooling of the intake air. A further development
of the Weber-Marelli fuel injection and engine management system has been
used. The new unit now has full closed-loop control of turbocharger boost.
In other words the boost characteristics are constantly compared to pre-mapped
settings and adjusted accordingly. This change has enabled an element of
'over-boost' to be designed in to the system, which allows the engine to
run higher than its standard 0.8 bar boost for short periods. The precise
over-boost characteristics have also been calculated and mapped. Other
engine changes include a lighter flywheel to reduce inertia and allow the
use of a competition multi-plate clutch, retuned engine mounts to minimize
NVH transmission, a redesigned cam belt cover, improved oil baffles for
the sump and a blue painted cam cover to denote the new engine type. Maximum
power of the YBT engine is 227 PS (DIN) at 6,250 rev /min with maximum
torque of 304 Nm (DIN) at 3,500 rev/min. o Suspension, steering and brakes
- tuned for safety and driver satisfaction Suspension steering and brake
components are broadly similar to those of the Sierra RS Cosworth. However
considerable development work has been carried out to achieve the best
results for the new model. From day one, the RS Cosworth suspension was
developed with the aim of improving on or matching the standards set by
the car's rivals. SVE's own engineers and an impressive array of racing
and rally drivers were called upon to make direct head-to-head comparisons
between the Ford and its competitors both on the road and around the Nurburgring
racing circuit. Precise handling characteristics From these early evaluations
it was determined that the RS Cosworth should have minimal cornering roll,
precise steering, outstanding high speed cornering stability and carefully
controlled compliance in the suspension bushes to provide positive and
responsive handling. To control compliance new suspension bushes with bi-directional
characteristics have been incorporated in the rear cross member mountings
and differential mountings. Rather than being the usual plain rubber design
these bushes have steel plate inserts which reduce their ability to compress
in one direction only. As a result. they retain the longitudinal compliance
necessary for comfort but reduce lateral compliance to prevent the rear
suspension assembly moving in relation to the car during cornering. Further
measures to optimise the handling characteristics include stiff front suspension
top mounting bushes and rigid rear semi-trailing arms which prevent any
chance of flexing under extreme loads. The mounting points for the trailing
arms on the rear cross-member have been specially reinforced. The front
anti-roll bar is 28 mm diameter and at the rear is a 22 mm anti-roll bar.
Gas-filled dampers are fitted all round. Specially formulated tyres Tyres
for the new RS Cosworth were chosen after a year long appraisal programme
which involved subjective evaluation on the road race circuit testing and
as a primary requirement excellent wet weather grip. The tyres finally
chosen were a version of Pirelli's P Zero specially formulated by the company
for the car. They are size 225/45ZR16 and are mounted on 8 x 16 inch five-spoke
alloy wheels . Power assistance is standard for the steering and a new
power steering pump with revised flow characteristics gives precise steering
response and excellent feel. The braking system comprises 278 mm front
and 273 mm rear ventilated discs with hydraulic assistance and ABS electronic
anti-locking. The front brake calipers are particularly rigid, front brake
pad area is generous for an extended service life and disc design has been
developed to optimise cooling. The pad material has been chosen to give
the best possible high temperature performance. With motorsport in mind
cooling ducts have also been built in to the front spoiler assembly. Refined
ABS braking The control logic of the Teves Mk 2 ABS has been developed
to give sensitive anti-locking control. This is aided by an additional
mercury switch type deceleration sensor. The ABS developments have allowed
the viscous couplings, used to limit slip in the centre and rear differentials
to be made stiffer without any sacrifice in anti-locking performance which
gives benefits to cornering grip particularly in poor surface conditions.
o Interior - unique instrumentation and high equipment levels Unlike previous
RS Cosworth models the new RS COSWORTH has its own, unique instrumentation.
The main instrument pack is similar to that of the Escort RS2000 however
a panel of three auxiliary gauges - for oil pressure, turbo boost and battery
voltage - is housed in a new binnacle located at the top edge of the facia.
The instruments themselves are new, too. Not only are the dials black on
white but they also feature a unique new form of instrument lighting, electro-luminescence.
This has been used in a slightly different form on the Aston Martin Virage
but is otherwise unique to the car industry being derived from aircraft
instrumentation. In this system there is no conventional instrument lamp;
instead the surface of the instrument itself glows green. This effect is
achieved by using a composite material for the surface which includes a
phosphor-coated layer. A 115 - 120 volt AC current is applied to this layer
which causes it to glow. (The AC current is created from the normal 12
volt DC battery voltage by a small inverter at the rear of the instrument).
The result is even instrument illumination which automatically adjusts
for ambient light conditions. Unique interior features The interior of
the RS Cosworth is derived from that of other Escort models but has a number
of unique features including a new style three-spoke leather-rimmed steering
wheel with horn buttons on the side spokes as well as the hub, a separate
centre console and a luxurious rear seat. The standard front seats are
unique to the RS Cosworth and provide excellent comfort over long distances
combined with positive lateral support. More sporting body-hugging Recaro
seats are either optional or standard equipment according to the market
concerned. Extensive standard equipment Standard equipment for the luxury
model includes power windows powered and heated door mirrors, Premium radio/cassette
unit a heated front screen heated screen washer jets, headlamp wash, glass
sunroof, central locking and remote boot release, opening rear quarter
windows, door bins, rear seat head restraints and central armrest and a
centre console with armrest and cassette stowage. All these items are deleted
in the Road Sport version of the RS Cosworth which is intended primarily
for those who want to buy the car with competition usage in mind. This
model features Recaro seats as standard, manually-operated windows and
door mirrors and fixed rear quarter windows. Options on the luxury model
include metallic paint Recaro seats, seat heating, air conditioning, a
CD player and leather trim. o Testing and manufacturing The RS Cosworth
has been through the same demanding pre-release testing programme as any
other Ford model and, in addition has had to undergo the tough programme
required to develop it for motorsport use. Following on from the original
concept vehicle, there have been a total of 12 prototype road cars, two
motorsport cars and four more rolling chassis. After these came three pre-functional
build cars and ten more functional build cars before some 50 cars went
into pre-production assembly. Exhaustive test procedures The Cosworth has
gone through Ford's own General Durability test procedure no less than
four times. This is a rigorous 40,000 km-long testing programme undertaken
at the Company's Lommel proving ground. In addition it has also been put
through the Improved Durability programme, a more severe version of this
procedure. The effects of the General Durability test circuit have also
been simulated on a special hydropulse test rig. Data is collected to show
the movements of each road wheel during General Durability testing and
these can be replicated on the special rig at the Company's research centre
in Dunton.