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)

Notes

M440i (G22/G23 Convertible/G26 Gran Coupe) is confirmed sold in both RWD and xDrive form in the US market (BMW dropped RWD only on some later facelift years per industry reporting) — both drivetrains are merged onto one row per model here since Dinan's own listing doesn't distinguish drivetrain for this part. Confirm current-model-year RWD availability with Speed Logic if ordering a very late build.

PART NUMBER

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

VEHICLE APPLICATIONS

Make	Model	Chassis	Engine	Years
BMW	M340i / M340i xDrive	G20	B58 3.0L Turbo I6	2020+
BMW	M440i / M440i xDrive	G22	B58 3.0L Turbo I6	2021+
BMW	M440i / M440i xDrive Convertible	G23	B58 3.0L Turbo I6	2021+
BMW	M440i / M440i xDrive Gran Coupe	G26	B58 3.0L Turbo I6	2021+