JDM RWD /// platform file
Mazda MX-5 (NA/NB) build guide
BP · 1.8 NA I4. What the stock hardware reliably supports, where it breaks first, and the fastest safe path to more.
The Mazda MX-5 (NA/NB) makes 133 hp stock at roughly 2,250 lb (16.9 lb/hp). Its stock internals are good for about 280 hp, the fuel system for around 190 hp, and its naturally aspirated setup tops out around 155 hp without forced induction. Below is the limit sheet carbuildcheck analyzes against, plus the platform's documented weak points.
01 Factory card
Stock power133 hp
Curb weight2,250 lb · 16.9 lb/hp
LayoutRWD
InductionNaturally aspirated
02 What stock parts support
Engine internals~280 hp
Fuel system~190 hp
Induction ceiling~155 hp
Clutch (manual)~180 hp
Transmission (auto/DCT)~220 hp
Cooling (sustained)~240 hp
Community-documented crank-hp planning figures, conservative by design. How these are used in the score →
03 Where it breaks first
The classic recipe holds: 6 to 8 psi on stock internals with a proper tune. Greed is what kills these engines.
Check sills and frame rails for rust before spending a dollar. The chassis is the platform.
04 The typical path
Intake → headers → tune → cams or forced induction. NA gains are honest but small; the big unlock is boost, and boost starts at the fuel system.
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