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

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. Imported from leading manufacturers around the world 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

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. Parts sourced to order are delivered within 30 days of the order date at the latest.

Warranty?
Manufacturing defects are covered by a 24-month BYC warranty, in addition to your legal rights.

Why BYC Performance?

BYC Performance is a Turkey-based performance tuning specialist sourcing premium carbon fiber parts from leading manufacturers around the world. 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 manufacturers around the world and undergo strict quality control.