Description
Designed for the Audi RS3 8V.2 and TT RS 8S equipped with the 2.5 TFSI EVO EA855 (DAZA) engine, the Untd. Performance 3.5″ Catless Downpipe is engineered for enthusiasts looking to reduce exhaust restriction, improve turbocharger response, increase horsepower and torque potential, and unleash a more aggressive version of the legendary 2.5T five-cylinder sound.
Featuring a large 3.5-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 DAZA engine and turbocharger to operate more efficiently while supporting substantially higher power levels.
Key Features
- 3.5″ Catless Design – Maximum Exhaust Flow:
The Untd. Performance Catless Downpipe features a large 3.5-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 3.5″ design allows the 2.5 TFSI EA855 DAZA 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 2.5T Five-Cylinder Sound:
The catless design significantly enhances the unmistakable character of the 2.5 TFSI five-cylinder, 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 EA855 engine. Precision-welded construction provides dependable performance for both street-performance and competition-oriented applications. - Direct-Fit Design:
Engineered specifically for compatible Audi RS3 8V.2 and TT RS 8S 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 replacement gaskets, bolts, and required installation hardware 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 EA855 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 400 HP factory-rated DAZA platform, using 91–93 octane (95–98 RON) pump fuel and stock turbochargers.
| Tuning Level | Estimated HP Gain | Estimated Output |
|---|---|---|
| Stock Tune | ~8–15 HP | ~408–415 HP |
| Stage 1 Tune | ~65–85 HP | ~465–485 HP |
| Stage 2 / Downpipe-Specific Tune | ~100–125 HP | ~500–525 HP |
Estimated Torque Gain: Approximately +10–20 WTQ on the stock calibration, +70–100 WTQ with Stage 1 software, and +100–140 WTQ with a downpipe-specific Stage 2 calibration. Actual torque output varies significantly depending on ECU/TCU calibration, fuel, boost targets, 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 465–485 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 3.5″ Catless Downpipe with a dedicated Stage 2 ECU calibration can produce approximately 500–525 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.
APR-published Stage 1 figures for the DAZA platform are commonly listed around 400 HP to approximately 475 HP, supporting the general Stage 1 range shown above. Actual results will vary depending on the specific software, fuel, vehicle, and supporting modifications.
⚠️ 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.
On the EA855 DAZA 2.5T, catless downpipes may also be associated with increased wastegate rattle at low RPM depending on the vehicle, turbocharger, exhaust configuration, and calibration.
Why Upgrade?
The factory catalytic converter is designed primarily around emissions compliance and quiet operation, creating additional exhaust restriction after the turbocharger. Replacing it with a large 3.5″ catless downpipe provides a significantly freer-flowing exhaust path.
The result is improved exhaust gas flow, reduced backpressure, sharper turbo response, a more aggressive five-cylinder 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 RS3 8V.2 – 2.5 TFSI EVO EA855 / DAZA – 400 HP
- Audi TT RS 8S – 2.5 TFSI EVO EA855 / DAZA – 400 HP
- Audi RS3 8V DAZA applications
- Audi TT RS 8S DAZA applications
- Designed for 2.5 TFSI EVO EA855 DAZA 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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