EcoBoost · 2.3 turbo I4. What the stock hardware is estimated to support, where it breaks first, and the honest path to more.
Same family, other generations and variants:Focus ST (Mk3)
The Ford Focus RS (Mk3) is rated 345 hp (EU 350 PS / 257 kW; US rating 350 hp SAE · EU market) at 6,000 rpm and weighs 3,525 lb (lightest kerb weight incl. 75 kg driver and 90 % fuel (Ford EU sheet)), or 10.2 lb/hp. On enthusiast estimates its stock internals are taken to about ~460 hp, the fuel system to around ~430 hp, and the stock turbo(s) are taken to about ~400–420 hp. Below: the sourced spec sheet, the limit sheet carbuildcheck analyzes against, and the platform's community-documented weak points.
Units
01 Spec sheet sourced
EngineEcoBoost · 2,261 cc · I4
Bore × stroke87.6 × 94 mm
Compression9.4:1
Inductiontwin-scroll turbo
Fuel systemdirect
Rated power345 hp · EU 350 PS / 257 kW; US rating 350 hp SAE · EU market @ 6,000 rpm
Torque325 lb-ft @ 2,000–4,500 (470 N·m on transient overboost) rpm
Redlinenot sourced in this audit
Stock boostnot sourced in this audit
Transmission6MT
DrivetrainAWD
Curb weight3,525 lb · lightest kerb weight incl. 75 kg driver and 90 % fuel (Ford EU sheet) · 10.2 lb/hp
rotating assembly ceiling · fails first: head gasket (early cars had a recall) and studs under sustained boost · 98 RON · no named source: site planning estimate · site planning figure ~460 hp; no named rod ceiling in this audit
Induction ceiling~400–420 hp
stock turbo / supercharger ceiling · fails first: stock turbo out of efficiency; Mountune's m400X sits at the top on 97+ RON (t2) · 97+ RON · source: Mountune, mTune SmartFlash m400X for the Mk3 Focus RS · the site plans on ~400 hp, Mountune's top stock-turbo tune; a Precision upgrade is rated 500 flywheel hp (t1)
Fuel system~430 hp
stock fuel-system ceiling · fails first: HPFP · 98 RON · no named source: site planning estimate · site planning figure; no named source in this audit
Clutch (manual)~380 hp
stock clutch torque capacity · fails first: stock clutch slip · no named source: site planning estimate · site planning figure; no named source in this audit
Cooling (sustained)~420 hp
thermal ceiling for sustained load · fails first: charge-air and RDU temperature · no named source: site planning estimate · site planning figure; no named source in this audit
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