Dinan Free Flow Axle-Back Exhaust System with Polished Tips for BMW M340i / M440i 2020-2024

Dinan's free-flow axle-back (D660-0085) is the polished-tip kit for G20 M340i and G22 / G23 / G26 M440i cars. It replaces the factory dual-outlet rear section with larger 76 mm T304 stainless tubing (versus 70 mm stock) and four 4-inch (102 mm) double-walled, clamp-on polished tips that sit in the factory valance. Dinan rates the change at plus 6 horsepower and plus 5 lb-ft of torque at 6,600 rpm, and the system is about 4 pounds lighter than stock.

The factory layout uses a single valve that shuts off the passenger-side tip when you want it quiet. Dinan adds a second valve and actuator on the opposite bank, reuses the original actuator, and sizes both valves at 76 mm (about 30 percent less restrictive than the OE pieces). When the valves are closed, gases stay in the muffler and leave through the inner tips; when they open under load, both outer pipes flow. M-Drive still commands the valves. The tubing is TIG welded and brush finished. Dinan lists labor at 2.5 hours.

Dinan titles the part for 2020-2024 BMW M340i / M440i and specifies G20 / G22 / G23 / G26. That covers B58 M340i sedans and M440i coupe, convertible, and Gran Coupe cars, including xDrive, through the last pre-LCI year Dinan lists. It is not for 330i / 430i (see D660-0091), M3 / M4, or 2025-up LCI G20 / G22 models. The black-ceramic-tip sibling is sold separately as D660-0085-BLK and is not merged here.

Emission code 5 applies. The packaged kit ships at 53 x 26 x 12 inches and 70.1 pounds (UPC 813725028767). Coverage follows Dinan's standard limited warranty: the remainder of the vehicle factory limited warranty (up to 4 years / 50,000 miles) or 2 years / unlimited miles, whichever is greater. The later DNN-prefixed listing shares this part number and redirects here.

Features

• Free-flow axle-back exhaust for G20 M340i and G22 / G23 / G26 M440i
• Plus 6 horsepower and plus 5 lb-ft of torque at 6,600 rpm
• Quad 4-inch (102 mm) polished, double-walled, clamp-on, laser-engraved tips
• 76 mm piping versus the factory 70 mm; about 4 lb lighter than stock
• Second 76 mm valve and actuator added so both banks flow evenly

What's Included

• Dinan Free Flow Axle-Back Exhaust (D660-0085)

Specifications

Questions about fitment? Call (310) 231-0292 or text (310) 886-3111.

Fitment Notes

• For 2020-2024 BMW M340i (G20) and 2021-2024 M440i coupe (G22), convertible (G23), and Gran Coupe (G26), including xDrive. Dinan titles the kit 2020-2024 BMW M340i / M440i.
• Not for 330i / 430i, M3 / M4, or 2025-up LCI G20 / G22 models.
• The black-ceramic-tip sibling is D660-0085-BLK.