Audi S5/A5 B9/B9.5 Prepreg Dry Carbon Fiber Rear Diffuser

Designed for Audi S5/A5 B9 and B9.5 owners, this Prepreg Dry Carbon Fiber Rear Diffuser brings premium carbon character and aerodynamic emphasis to your coupé, sportback, or cabriolet rear bumper. Manufactured in Europe and quality-controlled by BYC Performance, this Audi S5/A5 carbon rear diffuser bolts directly to OEM mounting points on both B9 pre-facelift and B9.5 facelift models.

If you're building a tasteful Audi A5/S5 B9 tuning build and want an elegant, balanced carbon upgrade over the factory plastic part, this flat-fin dry carbon rear diffuser is for you. Autoclave-cured prepreg carbon is noticeably lighter than wet-lay carbon, with superior structural integrity and excellent UV resistance. Complements the S5 B9/B9.5's 3.0 TFSI V6 single-turbo (349-354 hp) and the A5's 2.0 TFSI EA888 four-cylinder sporting-luxury character.

Key Features

• Prepreg Dry Carbon Technology: Pre-impregnated plies cured in an autoclave under high heat and pressure — homogeneous resin, a consistent weave.
• Flat-Fin Profile Design: Unlike our aggressive V2 version, this standard diffuser delivers a balanced, OEM-friendly flat-fin geometry that matches Audi's sporting-luxury DNA.
• High Strength: Carbon fiber offers very high strength for its weight.
• Aerodynamic Performance: Optimized fin profile organizes underbody airflow and contributes to rear-axle stability.
• 2x2 Twill Carbon Weave: Authentic carbon pattern under a high-gloss UV-protective clear coat.
• B9 + B9.5 Dual Fit: Mounts to factory Audi A5/S5 B9 (2016-2019) and B9.5 facelift (2019-2024) rear bumper points.
• UV & Chemical Protection: Long-life clear coat resists fading, cracking, fuel splash, and road tar.

Prepreg Dry Carbon vs. Wet Carbon — Which Is Better?

Most aftermarket carbon parts use wet lay-up, where resin is applied by hand and cured at room temperature — which can leave air voids and inconsistent weight. Prepreg dry carbon:

• Cured in an autoclave under high heat and pressure → a more consistent weave
• Made with a controlled resin ratio → lighter and stronger
• The production method widely chosen in motorsport
• Minimal UV fading over years of use

Vehicle Fitment

This Audi S5/A5 B9/B9.5 rear diffuser fits:

• Audi A5 Coupé B9 (2016-2019) and B9.5 (2019-2024) — 2.0 TFSI / 2.0 TDI
• Audi A5 Sportback B9/B9.5 (2016-2024) — 2.0 TFSI / 2.0 TDI
• Audi A5 Cabriolet B9/B9.5 (2017-2024)
• Audi S5 Coupé B9/B9.5 (2016-2024) — 3.0 TFSI V6 (349-354 hp)
• Audi S5 Sportback B9/B9.5 (2016-2024) — 3.0 TFSI V6
• Audi S5 Cabriolet B9/B9.5 (2017-2024) — 3.0 TFSI V6

Important notes:

• NOT compatible with RS5 B9/B9.5. RS5 (2.9 TFSI V6 biturbo, 444 hp) has unique aggressive rear bumper geometry; a separate RS5 carbon diffuser is available.
• NOT compatible with previous-generation B8/B8.5 A5/S5 (2008-2015).
• Our S5/A5 B9 V2 Rear Diffuser is a separate SKU — V2 fits B9 pre-facelift only and features more aggressive deep V-cut channels. This standard version fits both B9 and B9.5 with a flat-fin profile.

Technical Specifications

• Material: Prepreg Carbon Fiber (2x2 Twill Weave)
• Manufacturing: Autoclave Cure
• Finish: High-Gloss Clear UV-Protective Resin
• Color: Natural carbon weave black
• Origin: Europe

Installation Notes

Installation is a direct replacement of the factory part. Professional installation is recommended:

1. Raise the vehicle and remove rear bumper underbody screws.
2. Detach the OEM plastic diffuser from clips and bolts.
3. Test-fit the carbon diffuser for alignment.
4. Secure with supplied hardware to the manufacturer's recommended torque.
5. Verify exhaust tips are centered in diffuser cutouts (S5: quad oval; A5: single/dual).

Care & Maintenance

Wash with pH-neutral car shampoo. Apply carbon-safe sealant every 6 months. Keep pressure washer nozzle at least 30 cm from surface.

FAQ

Compatible with both B9 and B9.5?
Yes — this diffuser fits B9 pre-facelift (2016-2019) and B9.5 facelift (2019-2024); both generations share the rear bumper diffuser mounting geometry.

Does this fit the RS5 B9/B9.5?
No. RS5 has unique aggressive rear bumper geometry; a separate RS5 diffuser is available.

How is this different from the V2 Rear Diffuser?
The V2 is designed for B9 pre-facelift (2016-2019) only and features deep V-cut channels for an aggressive motorsport look. This standard diffuser fits both B9 and B9.5 with a balanced flat-fin profile.

Compatible with Coupé, Sportback, and Cabriolet?
Yes — all three body styles share the same rear bumper diffuser geometry.

Compatible with previous B8/B8.5 A5?
No. B8/B8.5 (2008-2015) uses different chassis and bumper geometry.

Will rain damage dry carbon parts?
No. Autoclave-cured prepreg carbon is fully waterproof and weather-resistant.

Shipping time?
In-stock items ship within 1-3 business days. International shipping available.

Warranty?
BYC Performance offers a 12-month manufacturer warranty.

Why BYC Performance?

BYC Performance is a Turkey-based performance tuning specialist sourcing premium carbon fiber parts from leading European manufacturers. Our catalog includes Audi S5/A5 carbon parts, Audi RS carbon diffusers, BMW M3 carbon diffusers, Porsche carbon spoilers, and more. All parts are sourced from leading European manufacturers and undergo strict quality control.