Audi S4 B9 Sedan 2017–2020 Carbon Fiber Rear Bumper Diffuser

Carbon Fiber Rear Bumper Diffuser for Audi S4 B9 Sedan

Bring a gloss carbon accent to the lower rear bumper of a compatible Audi S4 B9 Sedan. This replacement-style diffuser is intended to replace the original plastic diffuser, offering a coordinated finish alongside other carbon exterior details.

Vehicle Fitment

• Model: Audi S4 B9, Typ 8W, Sedan, 4-Door.
• Source-listed years: 2017, 2018, 2019 and 2020.
• Explicit exclusions: Audi A4 B9 Base and S line models.

Confirm VIN, production date, actual bumper revision, original diffuser shape and mounting points before ordering. The source does not separate facelift and regional bumper configurations, particularly at the end of the listed range. A 2020 registration or model year alone does not establish the correct bumper.

Avant, RS4, other body styles and years outside 2017–2020 are not independently confirmed. Modified bumpers and aftermarket exhausts require individual assessment. Compare exhaust outlet spacing, shape and clearance with the actual product; outlet dimensions and a compatible exhaust-tip list are not supplied.

Rear Access Sensor Warning

The source warns that installation may block the vehicle's rear sensor-operated access function, where fitted. Have the installer assess the actual sensor arrangement and verify operation after fitting. Do not assume uninterrupted hands-free rear access. Parking sensors and other rear equipment must also be checked for clearance and operation; compatibility with every equipment package is not documented.

Material and Finish

• 3×3 carbon fiber: Explicitly described in the source.
• Gloss finish: A smooth, reflective carbon surface.
• Double-layer UV-protected clear coating: The listed surface treatment.
• Shaping: The source describes 3D design, CNC moulding and test installation on a vehicle.

Dry-carbon construction, prepreg, resin, substrate, laminate thickness, curing method and measured weight savings are not specified. They are not inferred from carbon fiber alone. UV protection is a coating feature, not a permanent no-fading or no-discoloration guarantee. Source fit-testing does not guarantee exact alignment on every bumper revision.

Product Scope and Hardware

The source describes a replacement rear diffuser rather than an add-on lip or complete bumper. Exact diffuser section count is not itemized. Exhaust tips, reflectors, lights, sensor components and tools are not individually specified as included.

Fastener instructions differ within the source: the feature list says to reuse factory screws, while the detailed paragraph states that self-tapping screws are included. Confirm the supplied hardware and correct mounting method before installation. Do not assume existing holes are sufficient or that drilling and other modifications are unnecessary.

Professional Installation

Professional installation is recommended. Test-fit before drilling, altering mounting points or committing to final attachment. The original no-modification and quick-installation claims are not supported by a configuration-specific fitting guide.

• Verify actual S4 Sedan bumper configuration and the original diffuser mounting arrangement.
• Compare contours, attachment points, exhaust openings and supplied components before removing or modifying parts.
• Remove the original diffuser using an appropriate vehicle-specific procedure, protecting adjacent panels and wiring.
• Confirm whether factory fasteners, supplied self-tapping screws or other specified hardware are required.
• Inspect behind intended fastener locations before drilling; do not damage wiring, sensors or other components.
• Maintain appropriate clearance from hot exhaust components and moving or serviceable parts.
• Keep any fitted reflectors, lights, sensors and access points unobstructed.
• Check rear access sensor operation, relevant rear equipment and secure retention after installation.
• Check road and ramp clearance, and recheck attachment as directed by the installer.

Do not force misaligned parts into position or rely on unspecified adhesive as a substitute for the correct fasteners. No improved downforce, drag, handling, fuel economy, cooling or quantified weight saving is claimed without supporting test evidence. No fixed installation time or universal modification-free fitment is promised.

Care

Use a soft cloth and cleaning products suitable for coated carbon fiber. Avoid abrasive treatment and periodically inspect the coating, edges, exhaust clearance and mounting hardware.

Frequently Asked Questions

Will this fit an A4 B9 Base or S line?
No. Both are explicitly excluded in the source.

Does this replace the original diffuser?
Yes. The source describes replacement of the factory plastic diffuser, not a complete bumper replacement.

Can the rear hands-free access sensor be affected?
Yes. The source explicitly warns that its function may be blocked after installation.

Does installation use factory screws or self-tapping screws?
The source mentions both. Confirm the actual hardware and mounting requirements before fitting; drilling-free installation is not guaranteed.

Is this dry carbon fiber?
The source specifies 3×3 carbon fiber but does not establish dry-carbon construction.

Are exhaust tips included?
They are not individually listed as included. Confirm contents and outlet clearance before purchase.