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Ford Sierra RS Cosworth

PRODUCTION.- 1986; approximate number built: 5,500; assembled at Genk, Belgium with UK-built Cosworth engine, Borg Warner five-speed gearbox and Ferguson Viscous Coupling rear drive.                                                                                               


Type: Ford Cosworth YBB.
Capacity: 1,993 cc.
Bore/stroke: 90.82 mm x 76.95 mm.
Compression ratio: 8:1
Max power: 204 bhp at 6,000 rpm.
Max torque: 203 Ib/ft 4,500 rpm.
Specific output: 102.36 bhp per litre.
Power/weight ratio: 169.3 bhp/tonne.
Cylinders: four, in line
Cylinder head: Aluminium alloy.
Block: cast iron.

Valve gear: four valves per cylinder, twin overhead camshafts, belt-drive.  Fuel and ignition: Garrett Airesearch T03, compact air intercooler, Weber-Marelli microprocessor managed four injector injection and ignition.  Installation: Front, longitudinal.


Type: Rear drive, Viscous Coupling limited slip differential.

Gearbox: Borg Warner TS.

Internal ratios: lst, 2.95; 2nd, 1.94; 3rd, 1.34; 4th, 1:1 direct; 5th, 0.80.

Final drive: 3.65:1, 22,79 mph per 1,000 rpm in 5th.


Front: Independent by McPherson struts, lower track control arms (TCAs), coaxial coil springs, Fichtel & Sachs twin tube gas damper inserts, 28 mm diameter front anti-roll bar.

Rear: Semi-trailing arms, uniball joints, coil springs in front of axle, separate telescopic F&S gas rear dampers, 14 mm rear anti-roll bar.


Type: Power assisted, Cam Gears/TRW rack and pinion, lock to lock: 2.6 turns.


Front: 283 mm, vented discs.

Rear: 273 mm solid back discs.

System: Hydraulically assisted, Alfred Teves GmbH electronic anti-lock action.


Wheels: unique Rial (BBS style) alloys, 7 x 15 in.

Tyres: 205150 VR (Dunlop D40 was Original Equipment).



Type: 3-dr hatchback Sierra L with Phoenix-manufactured body kit and rear wing to Ford design, wheelarch extensions, side sills, front bumper/spoiler with flexible rubber extension, twin bonnet louvres, air intake between headlights.  Colour: Originally sold only in white, Moonstone blue metallic and black.

Construction: Steel monocoque with polyurethane and rubber body additions.  Dimensions: Length, 4,458 mm; width, 1,727 mm; height, 1,377 mm; wheelbase, 2,609 mm: front track, 1,450 mm; rear track, 1,470 mm; weight, 1,205 kg. 


PERFORMANCE AND ECONOMY (Manufacturer’s figures)


Max speed: 149.8 mph (240 km/h German homologation).
Acceleration: 0-60 mph, 6.47 sec; 50-70 mph (5
th gear), 7 sec.

Fuel consumption: 22.8 mpg urban; 38.2 mpg at constant 56 mph; 30.1 mpg at 75 mph.



Copyright Jan van Elderen