The B58 in your M340i or M440i has a great voice. The factory exhaust just keeps most of it to itself. Closed valve, one tip doing the talking, and a muffler tuned for the school run. You feel what this engine can do every time you roll into boost. You should be able to hear it too.
The Dinan Free Flow Axle-Back Exhaust replaces the rear section of the factory system on the BMW G20 M340i and G2X M440i with 76mm T304 stainless tubing, a second exhaust valve and quad 4 in. black ceramic tips. Dinan measured +6 HP and +5 lb-ft at 6600 RPM, and the finished system weighs 4 lbs less than stock.
Why the Dinan Axle-Back Exhaust Uses Two Valves
The factory system runs a single valve, and with the valve closed it drops one tip for quiet running. That approach does not work cleanly with four tips. Dinan's answer is a symmetric dual-valve layout with 76mm valves that are 30% less restrictive than the OE part. Valves open and exhaust flows through all four outer pipes for a deeper, fuller tone. Valves closed and everything routes through the muffler and out the two inner tips, so cold starts and highway cruising stay civil. You keep the factory valve control, so the car still switches between modes exactly as BMW intended.
Every pipe is 100% T304 stainless steel, TIG welded with a brushed finish. The quad tips are 102mm double-walled clamp-on units with a black ceramic coating that looks right against a dark or shadow-line rear end.
Axle-Back Exhaust Fitment, Install and Legal Status
This is a bolt-on axle-back. It uses the factory mounting points and Dinan quotes 2.5 hours of labor. Worried about emissions? Dinan states it is legal for sale or use on emissions-controlled vehicles because it does not affect vehicle emissions. Dinan part number D660-0085-BLK. Sold by AutoTecknic, an authorized Dinan dealer.
What's Included
- Dinan Free Flow axle-back exhaust with dual 76mm valves
- Quad 4 in. (102mm) double-walled black ceramic clamp-on tips
- Mounting hardware and band clamps
Key Features
- Dinan-tested +6 HP and +5 lb-ft at 6600 RPM
- 76mm tubing vs 70mm stock
- Dual 76mm exhaust valves, 30% less restrictive than OE
- Factory valve control retained for quiet low-speed running
- 100% T304 stainless steel, TIG welded, brushed finish
- Quad 102mm double-walled tips with black ceramic coating
- 4 lbs lighter than the factory system (68 lbs)
- Bolt-on install, about 2.5 hours
Vehicle Fitment
Fits the following B58-powered BMW models:
- BMW 3 Series / G20 Sedan (2020-2024): M340i, M340i xDrive
- BMW 4 Series / G22 Coupe (2021-2024): M440i, M440i xDrive
- BMW 4 Series / G23 Convertible (2021-2024): M440i, M440i xDrive
- BMW 4 Series / G26 Gran Coupe (2022-2024): M440i, M440i xDrive
Not for 330i or 430i models. Those cars use the Dinan valved axle-back built for the B48.
Installation Notes
A DIYer with a lift or good jack stands and basic hand tools can handle this, and a shop familiar with G2X cars will have it done in about 2.5 hours. Support the system properly while you work, since the complete assembly weighs 68 lbs. Follow the Dinan instructions included with the kit.
- Let the exhaust cool completely and raise the car safely on a lift or jack stands.
- Unplug the factory exhaust valve actuator connectors and loosen the clamp ahead of the rear section.
- Support the rear section, release it from the hangers and remove it.
- Transfer the valve actuators as directed, then hang the Dinan axle-back on the factory mounting points and connect it with the supplied band clamps.
- Fit the quad tips, align them in the valance, torque all clamps, reconnect the valve actuators and check for leaks with the engine running.
