Dinan Free-Flow Axle-Back Exhaust – BMW M5 (F90)

OVERVIEW

The F90 M5 impressed users and critics alike with its power and effortless delivery, but its stock exhaust note is best described as subdued. Dinan enlarged the tubing to 83 mm (against 80 mm stock) and fed it into a muffler using the absorption and reactive technologies common to every Dinan exhaust to cut backpressure — for more power and a sporty tone that stays civilized at low speed and turns pleasantly aggressive under hard acceleration, helped by the retained computer-controlled valves. Low-RPM drone is engineered out, so the cabin stays intimate rather than drowned.

The system is crafted entirely from T304 stainless steel, TIG welded and brush finished. The quad 4" (102 mm) clamp-on tips are double-walled, laser engraved and offered in black ceramic coating or polished stainless, keeping Dinan's signature straight-cut design so they fill the factory cut-outs cleanly.

SPECS

• Power: +6 HP @ 6600 RPM and +5 lb-ft @ 6600 RPM (Dinan lists peak gains of up to +10 HP and +8 lb-ft)
• 100% T304 stainless steel construction, TIG welded and brush finished
• Larger diameter piping for increased flow: 83 mm versus 80 mm stock
• Quad 4" (102 mm) clamp-on, double-walled, laser-engraved straight-cut tips in black ceramic coating or polished stainless
• Twin secondary exhaust valves, 76 mm diameter — 30% less restrictive than the OE valves
• Computer-controlled exhaust valves retained; stock actuators reused and valve operation unchanged, so tone is adjustable via M-Drive settings
• Engineered to reduce low-RPM drone
• Bolt-on installation with included mounting hardware
• Shipping weight: 63 lbs; carton approx. 50" × 34" × 13"
• Dinan published labor time: 2.4 hours
• Emissions: "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: on a vehicle still covered by the BMW new-car warranty, the remainder of that warranty (typically 4 years/50,000 miles); otherwise 2 years, unlimited mileage. Wear items, maintenance services and fluids are excluded.

PARTS INCLUDED

• 1 × D663-0345 muffler assembly
• 4 × engraved exhaust tips — D663-0573 polished or D663-0574 black
• 1 × D663-0346 hardware kit — 2 × 8 mm copper nuts, 2 × fixing bows, 2 × valve mount assemblies, 2 × 80 mm exhaust clamps, 4 × 80 mm clamps, 6 × M6 locknuts, 6 × M6 socket head screws, 6 × M6 button head screws, 18 × M6 flat washers, 6 × M6 wave washers

TECH RESOURCES

Additional Parts Required

• None. Dinan supplies the clamps, valve mounts, tips and hardware needed to fit this axle-back to the factory hangers.
• Basic hand tools and secure jack stands; allow roughly ten minutes for the exhaust to cool before removal. Installer-supplied.
• Optional: Dinan Resonator Delete Kit — 2018-2021 BMW M5, the matching midpipe section for the F90 M5.

Installation

• Dinan D660-0079 / D660-0079-BLK Free Flow Axle-Back Exhaust installation instructions (PDF) — INS660-0079: bill of materials, valve mount assembly, clamp positions and tip alignment.

Notes

• 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 catalogs this exhaust for the 2018-2023 F90 M5. Tip finish is selected by part number — check the variant you are ordering, and confirm fitment with Speed Logic before purchase.

PART NUMBER

• D660-0079 — polished laser-engraved tips
• D660-0079-BLK — black ceramic coated laser-engraved tips

VEHICLE APPLICATIONS