Audi S4 B9 Sedan 2017–2020 Carbon Fiber Rear Diffuser with Splitters

Carbon Fiber Rear Diffuser with Splitters for Audi S4 Sedan

Give the lower rear bumper of a compatible 2017–2020 Audi S4 Sedan a gloss carbon accent with this diffuser-with-splitters version. The source describes a replacement for the original plastic diffuser, rather than a complete rear bumper.

Vehicle Fitment

• Source-listed model: Audi S4 Sedan, 4-Door, B9 application.
• 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 contours and attachment points before purchase. The source does not distinguish every facelift or regional bumper configuration. A 2020 model or registration year alone does not confirm the correct bumper.

Avant, RS4, other body styles and years outside the stated range are not independently confirmed. Previously modified bumpers and aftermarket exhausts require individual assessment. Check actual exhaust outlet shape, spacing and heat clearance; outlet dimensions and a compatible exhaust-tip chart are not supplied.

Splitter Configuration and Product Scope

The source title identifies this as the diffuser with splitters version. It does not separately itemize splitter count, left/right pieces, whether the splitters are integrated or separate, or total component count. Confirm the supplied configuration before ordering rather than assuming a three-piece assembly or a separate splitter pair.

Complete bumpers, exhaust tips, reflectors, lights, sensor components and tools are not individually specified as included.

Rear Access Sensor Warning

The source explicitly warns that installation may block the rear sensor-operated access function, where fitted. Have the actual sensor arrangement assessed before fitting and verify operation afterward. Uninterrupted hands-free rear access is not guaranteed. Check any parking sensors and other rear equipment for clearance and correct operation as well.

Material and Finish

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

Dry carbon fiber, prepreg, resin, backing material, laminate thickness, curing process and measured weight savings are not specified. They are not inferred from carbon fiber cloth alone. UV protection is a coating feature, not a permanent no-fading or no-discoloration guarantee. Source test-fitting does not establish perfect alignment on every bumper revision.

Fasteners and Installation Requirements

The source contains differing fastener instructions: the features say to reuse factory screws, while the detailed paragraph says self-tapping screws are included. Confirm the actual supplied hardware, its quantity and the mounting requirements for the diffuser and splitters before installation. Do not assume existing holes are sufficient or that drilling is unnecessary.

Professional installation is recommended. The source's no-modification and quick-installation claims are not supported by a configuration-specific installation guide. Test-fit before altering parts, drilling or committing to final attachment.

Professional Setup Checklist

• Verify the actual S4 Sedan bumper configuration and original diffuser mounting arrangement.
• Inventory the diffuser, splitter sections and fasteners; identify the intended position of each supplied part.
• Compare contours, attachment points and exhaust openings before modifying components.
• Remove the original diffuser using an appropriate vehicle-specific procedure, protecting adjacent panels and wiring.
• Confirm which factory fasteners are reused and where any specified self-tapping screws are required.
• Inspect behind proposed fastener locations before drilling to avoid wiring, sensors and other components.
• Secure every supplied section with the correct mounting system; do not substitute unspecified adhesive for required fasteners.
• Maintain clearance from hot exhaust components and preserve access to serviceable parts.
• Keep any fitted lights, reflectors, sensors and access points unobstructed.
• Check rear access sensing, relevant rear equipment, road / ramp clearance and secure retention before driving.
• Recheck attachment as directed by the installer.

No improved downforce, drag, handling, fuel economy, cooling or quantified weight reduction is claimed without supporting test evidence. No fixed installation time, permanent finish retention 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, mounting hardware, splitter edges and exhaust clearance.

Frequently Asked Questions

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

How many splitters or sections are included?
The title specifies splitters, but the detailed source does not provide a piece-by-piece breakdown. Confirm contents and assembly arrangement before purchase.

Does it replace the original diffuser?
Yes. The source describes replacement of the factory plastic diffuser, not the full bumper.

Will the rear hands-free access sensor still work?
The source warns that its function may be blocked. Have the arrangement assessed and test it after fitting.

Are factory screws reused or self-tapping screws supplied?
Both appear in the source. Confirm actual contents and the correct fitting method; drilling-free installation is not established.

Is this dry carbon?
The source specifies 3×3 carbon fiber cloth without confirming dry-carbon construction.