Dinan Free Flow Axle-Back Exhaust – BMW M340i / M440i (B58)

OVERVIEW

Quad exhaust tips have long been a signature of BMW's most powerful letter, and a feature Dinan has traditionally reserved for M cars that already wore four tips from the factory. That changes with the Dinan Free Flow Axle-Back Exhaust for the G20 M340i and G22 M440i: the B58 platform earns the distinction, and the factory valance cleanly accommodates four 102mm straight-cut tips, offered in black ceramic coated or polished, laser engraved finishes.

The move to four tips also drove a change in valve strategy — Dinan integrated a second valve for symmetry and sound, in place of the factory's single valve that routes all gas out one tip when closed. Built entirely from TIG welded, brushed T304 stainless steel with larger 76mm tubing, the system delivers a deep, meaty tone through both outer pipes with the valves open, while closed valves force gas into the muffler for a quieter, drone-tamed cruise.

SPECS

• Maximum gain of +6 HP @ 6600 RPM (Dinan measured)
• Maximum gain of +5 lb-ft of torque @ 6600 RPM (Dinan measured)
• 100% T304 stainless steel construction, TIG welded and brushed
• 76mm main tubing versus 70mm factory tubing
• Quad 102mm (4 in.) clamp-on, double-walled, laser engraved tips in polished stainless or black ceramic coating
• 4 lbs lighter than the factory system
• Twin computer-controlled exhaust valves, 76mm diameter, approximately 30% less restrictive than the OE valves
• Factory exhaust valve actuator is reused and a second valve and actuator is added to the opposite side for even flow in either valve position
• Drone abatement technologies inside the muffler to limit low-RPM cabin resonance
• Dinan published installation time: 2.5 hours
• Emissions status per Dinan: "This part is legal for sale or use on Emissions Controlled Vehicles, Uncontrolled (Non-Emissions Controlled) Vehicles, and Racing Use Only Vehicles because it does not affect vehicle emissions and is not covered by emissions regulations."
• Dinan warranty: the remainder of the BMW new-car limited warranty (up to 4 years / 50,000 miles) or 2 years / unlimited mileage from purchase, whichever is greater; wear items, maintenance parts, improper installation and competition use are excluded

PARTS INCLUDED

• Dinan muffler assembly
• Left and right inlet pipes
• Four exhaust tips
• Hardware kit with clamps, valve mounts, limiters, fasteners and washers
• Exhaust valve actuator kit for G20 models, including one D661-0033 exhaust valve motor and related components

TECH RESOURCES

Additional Parts Required

• None. Dinan specifies no additional hardware for this part; all required mounting hardware is supplied with the kit.
• Installer-supplied tools only. Dinan lists torque specifications throughout the instructions.

Installation

• Dinan D660-0085 / D660-0085-BLK Free Flow Axle-Back Exhaust installation instructions (INS660-0085, Rev. F)

PART NUMBER

• D660-0085 – polished, laser engraved stainless tips
• D660-0085-BLK – black ceramic coated tips

VEHICLE APPLICATIONS