EURO RWD /// platform file
BMW M340i / M240i build guide
B58 · 3.0 turbo I6. What the stock hardware reliably supports, where it breaks first, and the fastest safe path to more.
The BMW M340i / M240i makes 382 hp stock at roughly 3,900 lb (10.2 lb/hp). Its stock internals are good for about 650 hp, the fuel system for around 520 hp, and the stock turbo(s) flow about 500 hp. Below is the limit sheet carbuildcheck analyzes against, plus the platform's documented weak points.
01 Factory card
Stock power382 hp
Curb weight3,900 lb · 10.2 lb/hp
LayoutRWD
InductionTurbocharged
02 What stock parts support
Engine internals~650 hp
Fuel system~520 hp
Induction ceiling~500 hp
Clutch (manual)~420 hp
Transmission (auto/DCT)~700 hp
Cooling (sustained)~500 hp
Community-documented crank-hp planning figures, conservative by design. How these are used in the score →
03 Where it breaks first
Same B58 rule as its Supra cousin: the high-pressure fuel pump walls near 500. 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, driveline before sticky tires.
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