Documentary photographPhoto: Charlie · CC BY 2.0 · resized and cropped · Registration identifier pixelated for privacy.
Engine redprint / verifiedYBB
2.0 L inline-4 · turbocharged · YBBLongitudinal front engine, rear-wheel driveTopology diagram · not to scale · based on the cited primary sources
The 204 PS three-door Sierra RS Cosworth provided Ford with a production base for Group A touring-car and rally competition.
R / production rarity
How rare is it?
A simple 1–5 rating based on completed worldwide production for this exact version. Price and desirability are not included.
Rarity ratingNot availableNo comparable worldwide production total
Production bandNot available
Production evidenceNo exact production total
ProducedWorldwide total used for the rating
Production total unavailable
A reliable worldwide figure is not listed in the references.
How the rating works
The rating uses five fixed production bands. Smaller production runs receive higher ratings. Exact totals and responsibly sourced estimates for this precise version can be rated. Plans, regional totals, lower bounds, disputed figures and broader-family totals remain visible but unclassified. The evidence description is kept separate from the rating so a source limitation cannot change how scarcity is measured.
Ford built the Sierra RS Cosworth (Sierra) from 1986–1987. The 204 PS three-door Sierra RS Cosworth provided Ford with a production base for Group A touring-car and rally competition. Its three-door fastback form and touring-car homologation special purpose locate it within a specific chapter of the marque’s performance history.
The focus here is the original three-door rear-drive Sierra RS Cosworth, excluding the RS500, later saloon, four-wheel-drive derivatives, race cars and replicas. That scope is important: familiar badges can cover several engines, markets and model years, while road cars and competition derivatives may share a name without sharing a usable technical specification.
The mechanical centre is the YBB, a 1,993 cc turbocharged inline-4. The period specification represented here is 150 kW (204 PS) and 277 Nm. Those figures stay attached to this configuration rather than blending regional tunes or later revisions.
The Sierra RS Cosworth pairs the Cosworth YBB turbocharged twin-cam four-cylinder with a five-speed manual and rear-wheel drive. The installation is longitudinal front engine, rear-wheel drive, working through a 5-speed manual. That combination determines throttle response, traction and the path by which induction, combustion and transmission sound reach the cabin and roadside.
Engineering and character
Useful listening markers include Cosworth YBB turbo four-cylinder, five-speed manual, rear-drive propeller shaft, three-door fastback cabin. A genuine cold start records cranking, first combustion and the transition to a settled idle; a warm restart is a different event and should be labelled as such.
Under acceleration, microphone position and engine load reveal different layers. An engine-bay or cabin recording can expose induction and valvetrain detail, while an exterior pass gives more weight to exhaust, tyres, turbocharger or supercharger behaviour and the acoustic effect of speed.
The Sierra identity also makes comparisons within the Sierra RS Cosworth family meaningful. Closely related editions may differ in intake hardware, boost control, gearing, catalysts, silencers or mass, so their recordings should not be treated as interchangeable merely because the body shell looks similar.
Surviving examples frequently carry replacement exhausts, wheels, suspension or engine parts. Those cars can still make valuable contributions when the changes are documented; the archive simply needs to distinguish a modified survivor from an evidenced factory-stock reference.
Legacy and identity
The 1986–1987 production period supplies another boundary for research. Manufacturers revised emissions calibrations, equipment and market availability during model runs, and historic output may appear in PS, kilowatts or regional horsepower standards. Keeping units and market context visible prevents false precision.
Body layout matters to sound as much as specification sheets suggest. The three-door fastback changes cabin volume, resonance and the listener’s distance from the powertrain. Engine position, driveline and body openings can therefore make related engines feel substantially different in use.
Period photographs establish design and historical context, but appearance alone cannot prove untouched mechanical condition. Originality should be described component by component, especially for intake, forced induction, catalysts, silencers, transmission and final-drive hardware that can alter performance and sound. Service records and dated photographs can make those distinctions clearer without asking readers to accept appearance as proof.
The Sierra RS Cosworth is therefore best understood as a connected mechanical identity: YBB, 5-speed manual, rear-wheel drive and the Sierra boundary. Preserving those elements gives readers a useful story now and gives future community recordings an exact historical home.
01
Model identity
The focus here is the original three-door rear-drive Sierra RS Cosworth, excluding the RS500, later saloon, four-wheel-drive derivatives, race cars and replicas.
02
Why it matters
The 204 PS three-door Sierra RS Cosworth provided Ford with a production base for Group A touring-car and rally competition.
