Active Autowerke B58N AFlow Catted Downpipe – BMW M340i / M440i (2025+)

OVERVIEW

This Active Autowerke downpipe fits the 2025-and-newer B58N (Gen-3) M340i and M440i with integrated GPF. It replaces the factory GPF downpipe with a 5 inch stainless steel unit running Active Autowerke's in-house AFlow high-flow catalyst, joined by a cast V-band and tapering to the OEM 80mm connection.

TIG-welded from 304 stainless steel, rated to withstand 1500°F and reach catalytic efficiency within about 9 seconds, for builds up to 950 horsepower, with no check-engine light and no performance tune needed.

SPECS

• 5" Active AFlow high-flow catalytic converter (in-house, not GESI), 400 cells per square inch — catted, no CEL
• 5" stainless steel, cast upper stainless V-band, stainless flex joint, tapering to 80mm OEM connection (never below the stock 80mm)
• 304 stainless steel, TIG-welded, 1.5mm wall; full 304 stainless converter including substrate
• Rated for builds up to 950 hp
• Withstands up to 1500°F; reaches operating efficiency within 9 seconds of start-up
• Bolts on — no cutting or welding required; no performance tune needed
• EPA registered and fully OBD2 compliant (1996 and newer) in 49 states — not legal in California
• Warranty: 5 yr / 50,000 mi on shell and tube ends; 2 yr / 25,000 mi on the catalytic core; original purchaser only; void with louder-than-stock burble
• Made in Miami, Florida

PARTS INCLUDED

• Catted AFlow downpipe
• Cast V-band connection
• Turbo flange gasket

TECH RESOURCES

Additional Parts Required

• None. Bolt-on; no cutting or welding, and Active Autowerke states no performance tune is needed.

Installation

• Active Autowerke catalytic converter break-in instructions (PDF) — follow this procedure on first start-up to avoid a check engine light being set in error.
• Professional installation recommended.
• Request an Install Appointment

Notes

• Replaces the OEM GPF downpipe; removing the stock GPF downpipe takes roughly 9–10 hours because the subframe must be dropped.
• Fits 2025+ B58N M340i / M440i only.
• Fitment applies to US-model cars only.
• EPA compliant in 49 states; not legal for sale or use in California (California Vehicle Code Sections 27156 and 38391).

PART NUMBER

• 11-062GA

VEHICLE APPLICATIONS