Description
Unlock the full performance potential of your BMW B58N Gen-3 engine with the Active Autowerke Signature AFlow Catted Downpipe, specifically engineered for M340i and M440i (2025 and newer, US models only). Designed to reduce exhaust backpressure, this downpipe improves turbo spool, increases horsepower, and maintains OEM-level emissions compliance using the included Active AFlow high-flow catalytic converter.
The factory B58N Gen-3 downpipe is restrictive, limiting turbo efficiency and exhaust flow. Active Autowerke’s solution utilizes 5” diameter TIG-welded 304 stainless steel piping, tapering down to 80mm to seamlessly connect with the OEM exhaust system. The included Active AFlow catalytic converter is EPA-registered, OBD2 compliant, and designed to operate without triggering a CEL while outperforming stock converters in high-flow and durability.
This bolt-on downpipe combines precision engineering, high-quality materials, and emissions-conscious design to deliver maximum performance with minimal compromise. It’s ideal for enthusiasts seeking increased horsepower, quicker turbo response, and a reliable aftermarket solution.
Key Features & Benefits
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No CEL – optimized catalytic efficiency using the included Active AFlow converter
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EPA-Registered High Flow Catalytic Converter – OBD2 compliant, 49-state legal (not California)
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5” Diameter Stainless Steel Piping – maximizes turbo output and reduces backpressure
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Quick Turbo Spool – large-volume design enhances boost response
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Rated up to 950 HP – suitable for high-performance forced induction applications
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TIG-Welded 304 Stainless Steel Construction – robust and long-lasting
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Casted Upper V-Band Flange – ensures precise OEM-style fitment
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Ultra High Flow Catalyst – 400 cells per square inch for maximum efficiency
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Operational Efficiency – reaches full catalytic function within 9 seconds of startup
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Durability & Safety – withstands temperatures up to 1500°F, protects occupants from harmful emissions
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Warranty – 5 years / 50,000 miles (shell/tube ends), 2 years / 25,000 miles (catalyst core)
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Made in Miami, Florida
Installation Notes
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Designed for US-spec BMW B58N Gen-3 M340i / M440i (2025+)
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Requires subframe removal; labor time approximately 9–10 hours
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Bolt-on installation, no cutting or welding required
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Professional installation recommended
Active Autowerke B58N Signature Downpipe Benefits
The speed of your turbocharger is limited by exhaust backpressure. Active Autowerke’s 5” signature downpipe relieves this restriction, resulting in quicker spool, improved horsepower, and increased torque. Using the high-flow GESI catalytic converter, emissions are managed without sacrificing performance.
Engineered for daily driveability, durability, and long-term performance, this downpipe offers an affordable, high-quality solution for B58N enthusiasts looking to maximize their vehicle’s potential.
Vehicle Fitment
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BMW M340i / M440i B58N Gen-3 – 2025 and newer (US model only)
