Active Autowerke B58 Catted Downpipe for BMW M240i, 340i, 440i (F3x/F4x, 2024 & Earlier)

Active Autowerke BMW B58 Catted Downpipe – now includes turbo flange gasket

SHIPPING NOW. Please note that we install the gasket into the downpipe flange as some customers were damaging the gasket on installation.

NOTE: Fitment applies to US model cars only unless specifically stated. We cannot guarantee fitment to non-US model cars.

BMW introduced a new valvetronic, single turbo version of its direct-injection engine for the later F-Chassis models beginning in 2016 and carried over to the G-chassis models. The Active Autowerke B58 downpipe for the M340i and M440i helps unleash some of the potential that is restricted by the OEM downpipe.

Turbochargers are powered by spent exhaust gases created during the combustion process. The quicker these gases are evacuated, the better. Unfortunately, the factory down pipe in the B58 is quite restrictive, which results in slower exhaust gases and slower turbo spool.

The Active Autowerke B58 Signature down pipe utilizes 4.5 diameter stainless steel piping in order to provide more power, quicker spool, and extreme durability. It then tapers down to 3.5″ where we’ve incorporated a stainless flex joint and then down to 80mm to meet the OEM exhaust system. We never drop the diameter less than the stock diameter of 80mm. 

This variant includes a 4.5″ Active Aflow catalytic converter that will NOT produce a CEL for cat efficiency guaranteed by Active Autowerke (full replacement within first two years of ownership).

The Active Aflow super high output catalytic converter features full 304 stainless steel construction, including the substrate. Active Aflow Catalytic Converters are EPA registered and compliant in 49 states and fully OBD2 compliant, perfect for use on 1996 and newer vehicles. Active’s proprietary precious metal loading technology ensures greatly reduced emissions, eliminating most “Check Engine Lights” due to cat efficiency errors. These high flow catalytic converters outperform stock converters and provide a reliable solution to the most common catalytic converter problems.
The Active Aflow Catalytic Converters are rated for engines putting out up to 800 horsepower while maintaining a high flow capacity. The reduced back-pressure from this high flow catalytic converter will allow you to maximize your engines horsepower without the harmful emissions. Say goodbye to Check Engine Lights for cat efficiency and failed emissions tests!
Please Note: These catalytic converters are not legal for use on vehicles registered in the state of California as a result of California Vehicle Code Section 27156 and 38391.

NOTE: Federal law prohibits the tampering of an emissions control device. Mobile Source Enforcement Memorandum 1A, allows for aftermarket parts to be used in the repair or replacement of emissions control systems, provided the emissions aren’t adversely affected. There is no mention or reference to cell density or converter volume dimension. The Active Aflow catalytic converter will produce emissions that will meet the standards set by the EPA, not CARB.

Features:

• NO CEL for catalytic efficiency when using this downpipe

• Active EPA registered high flow and fully OBD2 compliant

• Casted upper stainless steel V-Band for precise fitment

• 4.50″ diameter piping allows for maximum power output

• Quicker turbo spool

• Rated for up to 800 hp applications 

• Withstands up to 1500 F

• Can reach operational efficiency within 9 seconds of startup

• Easily bolts-on no cutting or welding required

• Durable construction from TIG welded 304 stainless steel

• Precise fitment

• Ultra high flow 400 cell per square inch catalyst

• EPA compliant for use on OBD2 vehicles (1996 and newer) except in California

• 304 stainless steel substrate is furnace braised to the mantle for outstanding durability

• Active proprietary precious metal loading technology ensures greatly reduced emissions

• Ideal for Forced Induction Applications with no loss of HP

• Both passengers and drivers are safe from harmful emissions and noise

• Covered by 5 Year / 50,000 Mile Warranty (on shell and tube ends) and 2 year / 25,000 Mile Warranty on the Catalytic core to original purchaser only – NOTE: warranty will be null and void if your car has excessive burble (greater than stock) as that physically destroys the catalytic core

• Made in Miami, Florida

Active Autowerke B58 Signature Downpipe Benefits

The speed of a turbo’s impeller wheel is limited by exhaust back pressure. A larger down pipe relieves some of this pressure, resulting in quicker and more efficient spool. With Active Autowerke’s Signature downpipe, your B58 can rev quicker, and deliver more horsepower and torque.

Minimizing back pressure while retaining daily drive-ability was the goal of our B58 downpipe. Owners can now upgrade to a product that is affordable, reliable, and easy to install.

After months of research and development, our engineers settled on a 4.5 diameter pipe which utilizes the least number of bends possible. The large volume helps the turbo spool as quickly as possible by eliminating back pressure during spool up. We are ushering in a new era in performance where we maintain air control standards without significant losses in power by using the Active super high output catalytic converter in our signature downpipe.

Constructed entirely from 304 stainless steel with 1.5MM wall thickness, we are confident that you’ll be pleased with how robust and durable this down pipe is. Trouble-free installation and a long lifespan ensure that you’ll enjoy many miles of performance with your B58!