Description
Designed for the Audi A4 and A5 B9 equipped with the 2.0 TFSI EA888 Gen3B engine, the Untd. Performance 3″ Catless Downpipe is engineered for enthusiasts looking to reduce exhaust restriction, improve turbocharger response, increase horsepower and torque potential, and give the B9 2.0T a more aggressive exhaust note.
Featuring a large 3-inch diameter and a completely catless design, this downpipe significantly increases exhaust flow compared to the restrictive factory catalytic converter. When combined with the appropriate ECU calibration, the increased flow allows the EA888 turbocharger to operate more efficiently while supporting increased power levels.
Key Features
- 3″ Catless Design – Maximum Exhaust Flow:
The Untd. Performance Catless Downpipe features a large 3-inch diameter designed to maximize exhaust flow and minimize restriction after the turbocharger. Removing the restrictive factory catalytic converter creates a freer-flowing exhaust path and helps reduce exhaust backpressure. - Improved Turbo Response & Performance:
The high-flow 3″ design allows the 2.0 TFSI EA888 Gen3B turbocharger to expel exhaust gases more efficiently. When paired with an appropriate ECU tune and supporting modifications, the reduced restriction can help improve turbo response, throttle response, horsepower, and torque. - Aggressive 2.0T Sound:
The catless design enhances the character of the Audi 2.0 TFSI, producing a deeper, louder, and more aggressive exhaust tone. Turbocharger spool and exhaust notes become more pronounced under acceleration. - Durable Construction:
Built to withstand the high temperatures, exhaust pressure, and demanding conditions generated by the turbocharged EA888 engine. Precision-welded construction provides dependable performance for both street-performance and competition-oriented applications. - Direct-Fit Design:
Engineered specifically for compatible Audi A4 and A5 B9 2.0T applications, providing a direct replacement for the factory downpipe and designed to work with suitable OEM and aftermarket exhaust components. - Installation Hardware Included:
The downpipe includes bolts to help ensure a proper fit and secure installation. Supplied hardware helps simplify installation while providing the necessary components for proper sealing and mounting. - Tune Recommended / Required for Optimal Performance:
An ECU tune is strongly recommended and may be required when installing a catless downpipe. Proper calibration allows the EA888 and turbocharger to take full advantage of the increased exhaust flow while optimizing boost control, fueling, ignition timing, throttle response, and overall performance.
Estimated Performance Gain
Actual results will vary depending on ECU calibration, fuel quality, vehicle condition, supporting modifications, and dyno methodology. The following figures are estimated crank horsepower and torque gains based on the 252 HP factory-rated Audi A4 B9 45 TFSI, using 91–93 octane (95–98 RON) pump fuel and stock turbochargers.
| Tuning Level | Estimated HP Gain | Estimated Output |
|---|---|---|
| Stock Tune | ~5–10 HP | ~257–262 HP |
| Stage 1 Tune | ~55–75 HP | ~307–327 HP |
| Stage 2 / Downpipe-Specific Tune | ~70–90 HP | ~322–342 HP |
Estimated Torque Gain: Approximately +5–15 WTQ on the stock calibration, +55–80 WTQ with Stage 1 software, and +70–95 WTQ with a downpipe-specific Stage 2 calibration. Actual torque output varies depending on ECU/TCU calibration, fuel, boost targets, supporting modifications, and dyno methodology.
Stock Tune: A catless downpipe can reduce exhaust backpressure and provide slightly quicker turbo spool, but the factory ECU calibration will not fully utilize the additional exhaust flow. A Check Engine Light is expected due to catalyst-efficiency/rear-O2 monitoring.
Stage 1 Tune: An ECU remap optimized for the factory hardware can produce approximately 307–327 HP. The downpipe is not required to achieve the Stage 1 power level, as the primary gains come from the ECU calibration.
Stage 2 / Downpipe-Specific Tune: Combining the Untd. Performance 3″ Catless Downpipe with a dedicated Stage 2 ECU calibration can produce approximately 322–342 HP. This represents the largest estimated gain of the configurations listed above, with the tune specifically calibrated to take advantage of the freer-flowing downpipe.
Note: Audi A4/A5 B9 models from 2021 onward may be factory-rated at approximately 261 HP, so baseline and tuned output can differ from the figures shown above.
Performance figures are platform estimates based on typical published tuner figures and are not re-verified dyno results for this specific product.
⚠️ Check Engine Light Warning
Because this product removes the factory catalytic converter, installing a catless downpipe can trigger a Check Engine Light (CEL) due to catalyst-efficiency and rear-O2 sensor monitoring.
A properly calibrated ECU tune may be required to address catalyst monitoring and allow the engine management system to operate correctly with the modified exhaust system.
Why Upgrade?
The factory catalytic converter is designed primarily around emissions compliance, noise reduction, and OEM operating requirements, creating additional exhaust restriction after the turbocharger. Replacing it with a large 3″ catless downpipe provides a significantly freer-flowing exhaust path.
The result is improved exhaust gas flow, reduced backpressure, sharper turbo response, a more aggressive 2.0T exhaust note, and greater power potential when paired with the appropriate ECU calibration.
For enthusiasts running a Stage 2 performance tune, the downpipe becomes an important supporting modification that allows the calibration to take advantage of the increased exhaust flow.
Compatibility
- Audi A4 B9 45 TFSI – 2.0 TFSI EA888 Gen3B – 252 HP
- Audi A5 B9 45 TFSI – 2.0 TFSI EA888 Gen3B
- Audi A4 B9 2.0T applications
- Audi A5 B9 2.0T applications
- 2021+ models with approximately 261 HP factory rating
- Designed for compatible EA888 Gen3B 2.0 TFSI configurations
- Compatible with suitable OEM and aftermarket exhaust systems
⚠️ Important Notice
- CATLESS / OFF-ROAD / COMPETITION USE ONLY
- Removing the catalytic converter may cause a Check Engine Light.
- An ECU tune is strongly recommended and may be required for optimal performance and proper catalyst-monitoring calibration.
- The Stage 2 configuration requires a downpipe-specific ECU calibration.
- This product is intended for off-road, track, racing, and competition applications only.
- Catless exhaust components may not comply with federal, provincial/state, or local emissions regulations and may not be legal for use on public roads in Canada or the United States.
- Estimated horsepower and torque figures are provided for reference only. Actual results vary based on fuel quality, ECU calibration, supporting modifications, engine condition, turbocharger condition, drivetrain losses, and testing methodology.
- Professional installation and ECU calibration are recommended.
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