Description
Get improved exhaust flow and a more aggressive V8 character with the Untd. Performance Catless Manifold / Headers for the Audi RS5 B8/B8.5 4.2L FSI V8. Designed to replace the restrictive factory exhaust manifolds and catalytic-converter assemblies, these headers provide a significantly freer-flowing path for exhaust gases and help reduce backpressure throughout the system.
The naturally aspirated 4.2L FSI V8 responds differently to exhaust modifications than a turbocharged engine. While a catless manifold setup will not produce the same large gains associated with forced-induction applications, reducing exhaust restriction can improve high-RPM breathing, throttle response, and overall engine character. The biggest benefits are typically realized when combined with appropriate ECU calibration and supporting exhaust modifications.
Key Features
- Catless Design – Maximum Exhaust Flow:
Eliminates the factory catalytic restriction from the manifold/header section, providing a substantially freer-flowing exhaust path and reducing backpressure. - Improved High-RPM Breathing:
The 4.2L naturally aspirated V8 relies on efficient exhaust flow to maintain power as engine speed increases. The freer-flowing design helps improve exhaust evacuation and high-RPM airflow. - Sharper Throttle Response:
Reduced exhaust restriction can contribute to improved throttle response and a more immediate feeling through the rev range. - Aggressive 4.2L V8 Sound:
Removing the factory catalytic restriction produces a significantly louder and more aggressive exhaust note, allowing the characteristic high-revving Audi V8 sound to come through more prominently. - Performance-Oriented Header Design:
Designed as a performance replacement for the factory manifold/catalyst assemblies, with the goal of improving exhaust flow while maintaining compatibility with the RS5 platform. - Direct-Fit Application:
Designed specifically around the Audi RS5 B8/B8.5 4.2L FSI V8 platform. - Tune Recommended for Optimal Performance:
ECU calibration is strongly recommended after installation. Because the factory catalytic converters are removed, catalyst-efficiency and rear-O2 monitoring may trigger a Check Engine Light.
Estimated Performance Gain
Because the RS5 4.2L is naturally aspirated, gains from exhaust manifolds/headers are generally more modest than those seen on turbocharged engines. The largest improvements are expected at higher RPM where reduced exhaust restriction can provide better cylinder evacuation and airflow.
| Configuration | Estimated HP Gain | Estimated Torque Gain | Estimated Output |
|---|---|---|---|
| Stock Tune | ~8–15 HP | ~5–10 lb-ft | ~442–449 HP |
| Stage 1 Tune | ~15–25 HP | ~10–18 lb-ft | ~449–459 HP |
| Stage 2 Tune | ~20–30 HP+ | ~15–22 lb-ft | ~454–464 HP |
Performance estimates are approximate and assume a healthy factory 4.2L FSI V8 with appropriate supporting hardware. Actual results will vary depending on ECU calibration, intake/exhaust configuration, fuel quality, engine condition, and dyno methodology.
⚠️ Check Engine Light Warning
Because these headers are catless, removing the factory catalytic converters can trigger a Check Engine Light due to catalyst-efficiency and rear-O2 sensor monitoring.
A compatible ECU calibration is strongly recommended. Depending on the tuning strategy, the rear-O2/catalyst monitoring may need to be appropriately calibrated or disabled.
Why Upgrade?
The factory RS5 exhaust manifold/catalyst assembly is designed around emissions compliance, noise control, and OEM operating requirements. Replacing it with a freer-flowing catless manifold/header setup removes a significant restriction directly at the exhaust side of the engine.
On the naturally aspirated 4.2L FSI V8, the result is primarily improved exhaust flow, high-RPM breathing, throttle response, and sound rather than the dramatic power increase possible on a turbocharged engine.
Combined with a freer-flowing exhaust system and proper ECU calibration, the headers can help the 4.2L V8 operate with fewer exhaust-flow restrictions and provide a more aggressive motorsport-inspired exhaust character.
Compatibility
Designed for:
- Audi RS5 B8 4.2L FSI V8
- Audi RS5 B8.5 4.2L FSI V8
- 4.2L naturally aspirated FSI V8 applications
Please verify your exact model year, engine configuration, manifold design, and exhaust connection points before ordering.
⚠️ Important Notice
- CATLESS / OFF-ROAD & COMPETITION USE ONLY
- Removing the catalytic converters may make the vehicle non-compliant with emissions regulations and unsuitable for use on public roads.
- A Check Engine Light may occur after installation.
- ECU tuning is strongly recommended for optimal performance.
- Horsepower and torque figures are estimated and not guaranteed.
- Professional installation and ECU calibration are recommended.
- Verify fitment and supporting hardware before installation.
- Untd. Performance is not responsible for emissions compliance, inspection requirements, or legal use of this product.
nikolaitchoukn@hotmail.com –
Man, the tone is just on another game. One hell of a mission to get them installed, but fully worth it