EURO AWD /// platform file
BMW M240i xDrive / M340i (B58) build guide
B58 · 3.0 turbo I6. What the stock hardware is estimated to support, where it breaks first, and the honest path to more.
The BMW M240i xDrive / M340i (B58) is rated 382 hp (SAE, M240i xDrive · US market) at 5,800–6,500 rpm and weighs 3,871 lb (US curb, M240i xDrive Coupé (RWD M240i and M340i not sourced)), or 10.1 lb/hp. On enthusiast estimates its stock internals are taken to about ~650–700 hp, the fuel system to around ~500 hp, and the stock turbo(s) are taken to about ~500 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
EngineB58 · 2,998 cc · I6
Engine codeB58B30O1
Bore × strokenot sourced in this audit
Compressionnot sourced in this audit
Inductionsingle twin-scroll turbo
Fuel systemdirect
Rated power382 hp · SAE, M240i xDrive · US market @ 5,800–6,500 rpm
Torque369 lb-ft @ 1,800–5,000 rpm
Redlinenot sourced in this audit
Stock boostnot sourced in this audit
Transmission8-speed Sport automatic
DrivetrainAWD
Curb weight3,871 lb · US curb, M240i xDrive Coupé (RWD M240i and M340i not sourced) · 10.1 lb/hp
GenerationG42 (M240i) · G20/G21 (M340i) · 2022– (M240i xDrive Coupé, the sourced car); M340i 2020– shares the 382 hp US rating
Verified againstBMW USA PressClub, The new 2022 BMW 2 Series Coupe (primary, read 2026-09-06) · The rated power and the mass each rest on one document.
02 What stock parts support enthusiast estimates
Engine internals~650–700 hp
rotating assembly ceiling · fails first: rods, at wheel figures beyond the stock fuel system · 93 AKI / E85 mix · source: bmwtuning.co, How to build a 500 hp B58 · 600–650 whp on stock internals (t2) is roughly 750–810 crank at the 20 % AWD loss the site uses; the site plans on ~650 hp crank, well inside that
Induction ceiling~500 hp
stock turbo / supercharger ceiling · fails first: stock turbo out of efficiency · 95 RON / 93 AKI · source: MHD Tuning, B58 Super License (stage map ratings by generation) · MHD rates a gen-2 stage 2 on 95 RON at 500 hp crank; the site plans on that figure
Fuel system~500 hp
stock fuel-system ceiling · fails first: high-pressure fuel pump near 500 hp · 93 AKI · source: bmwtuning.co, How to build a 500 hp B58 · bmwtuning.co calls fueling the big limitation and puts pump-gas builds near 400–415 whp (500–520 crank at 20 % AWD); the site plans on 500 hp before port injection
Transmission (automatic)~700 hp
gearbox / driveline rating · fails first: ZF 8HP clutch packs at torque · no named source: site planning estimate · site planning figure; no named source in this audit
Cooling (sustained)~500 hp
thermal ceiling for sustained load · fails first: charge-air heat soak · no named source: site planning estimate · site planning figure; no named source in this audit
Tuning limitsenthusiast estimates, crank hp on the stated fuel; sources: MHD Tuning, B58 Super License (stage map ratings by generation); bmwtuning.co, How to build a 500 hp B58; method: the analyzer plans on the lower bound of each range
Planning figures, conservative by design, never a manufacturer claim. How these are used in the score →
03 Where it breaks first community-documented
Same B58 rule as its Supra cousin: the high-pressure fuel pump walls near 500 hp (bmwtuning.co). Fueling before bigger-turbo dreams.
xDrive cars put power down better than the spec sheet suggests; RWD cars should budget for traction first.
04 The typical path
Stage 1 tune → intake → downpipe → intercooler → Stage 2 tune. Fueling before E85; a automatic gearbox calibration before sticky tires.
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power outgrows the stock wheel and tire package firstWheelHero ↗Partner linkUS
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