The vehicle shell was based on the 4 door Sierra Sapphire shell with boot.

The vehicle was available from 1990 in both RHD (Right Hand Drive) for the UK market, and LHD (Left Hand Drive) for Europe.

As per the Sierra Sapphire 2WD Cosworth with the following differences:

A Cosworth revised head and stronger cylinder block to prevent head gasket failure which affected the earlier Sierra 3 door Cosworth, and Sierra Sapphire 2WD Cosworth.

The revised head featured an improved combustion chamber design and was sturdier around the exhaust valves, where head gasket failure was likely to occur.

An improved cast iron exhaust manifold was used to reduce vibration and the chance of stress induced cracks.

This 4WD Cosworth model's intercooler was enlarged by 25% to further aid cooling. Higher engine output power had to be achieved to overcome the restriction of the catalytic converter.

Although engine power output was improved over the 2WD model, any speed gain was lost due to front wheel transmission loses. Output power was claimed as 224 bhp at 6000 rpm.

The engine was converted to run on Unleaded Fuel and this Unleaded unit used a catalytic converter on the exhaust system. This restricted the exhaust system flow considerably. Fuel injection used Weber/Marelli equipment.

All Cosworth engines are fitted with hardened valve seat inserts and can therefore run continuously on unleaded fuel. With ordinary unleaded petrol it is necessary to retard the ignition by 4 Degrees. A power loss of approximately 10 bhp will be experienced after the ignition is retarded. Retarding the ignition may not be necessary if the engine is always run on Super unleaded fuel.

Red coloured engines indicate a 4 Star petrol unit and green an Unleaded Petrol only version.

The main area of modification over the 2WD model was obviously due to powering the front wheels. Hence the transmission was a complete new design with drive rods to the front two wheels. A mechanical Anti-Lock Braking System (ABS) was also employed on this new 4WD model.

As per the Sierra Sapphire 2WD Cosworth with the following differences:

• Different style bonnet vents.
• New style alloy wheels with locking hub caps.
• Driving lamps mounted within the front spoiler.

Available colours where:

• White
• Graphite Grey
• Metallic Magenta
• Smokestone Blue

Optional extras where:

• Black leather interior
• Air Conditioning
• On board fuel computer
• Electric tilt and slide sun roof.

The Sierra Sapphire 4WD was produced until 1993, when sadly the Sapphire was discontinued to make way for Fords new rep-mobile the Mondeo (yawn, yawn!). Although Ford's alliance with Cosworth continued in the form of the MK5 Escort RS Cosworth.

UK price guide (Sterling)

Condition       Excellent   Good    Average

Sterling         12000      9000     8000

Note: The FORD Sierra Sapphire Cosworth 4WD was produced on G to K-registration plates in the UK.

For further details see Vehicle Registration Plate Guide.

NOTE: For turbo longevity it is recommended that the Sierra Cosworth along with all other turbocharged RS models run with fully synthetic oil. These types of oil give the necessary engine protection for the high temperatures attained in turbocharged vehicles. The following viscosity synthetic oils are recommended: 5w50, 10w40, 15w50, 10w60.

The Sierra Sapphire Cosworth was based on the Sierra Sapphire of the time. Further details of which can be found in the Ford Sierra 1982 Workshop manual.