xDrive RSS
BMW M5 F90 Downpipe Guide — S63 4.4TT Catted vs Catless, Stage 2 Power & Install
The BMW F90 M5 uses the S63B44T4 — a 4.4-litre twin-turbo V8 that produces 591–617 HP from the factory depending on variant. It is one of the most potent sedans ever built, and it has substantial untapped potential locked behind factory exhaust restrictions. The stock catalytic converters downstream of each turbocharger are the primary bottleneck, and replacing them with performance downpipes is the foundation of any serious M5 build. Why the S63 Needs Downpipes The S63 positions its two twin-scroll turbochargers outboard of the cylinder banks in a traditional hot-outside-vee layout. Each turbo feeds exhaust through its own catalytic converter...