Description
Designed for the Mercedes-AMG A45 S and CLA45 S W177 2.0T M139, the Untd. Performance Catless Downpipe is an ideal upgrade for enthusiasts looking to reduce exhaust restriction, improve turbocharger response, increase horsepower potential, and unleash a more aggressive version of the AMG 2.0T sound.
By removing the restrictive factory catalytic converter and providing a significantly freer-flowing exhaust path from the turbocharger, the Untd. Performance Catless Downpipe helps reduce exhaust backpressure and allows the high-output M139 engine to expel exhaust gases more efficiently. When paired with an appropriate ECU tune, this downpipe can help unlock substantially greater performance from the AMG 2.0T platform.
Key Features
Catless Design – Maximum Exhaust Flow:
The Untd. Performance Catless Downpipe eliminates the restrictive factory catalytic converter, creating a significantly freer-flowing exhaust path from the turbocharger. Reduced exhaust restriction helps minimize backpressure and allows the M139 engine to move exhaust gases more efficiently.
Improved Turbo Response & Performance:
The freer-flowing design allows the turbocharged 2.0T engine to evacuate exhaust gases more efficiently. Reduced backpressure can help improve turbocharger response, throttle response, horsepower, and torque, particularly when combined with an appropriate ECU calibration.
Aggressive AMG 2.0T Sound:
The catless design significantly enhances the character of the M139 engine, producing a deeper, louder, and more aggressive exhaust tone. Turbocharger spool and exhaust volume become more pronounced under acceleration.
High-Performance M139 Compatibility:
Designed around the Mercedes-AMG M139 2.0T turbocharged four-cylinder, including high-output A45 S and CLA45 S W177 applications.
Durable Construction:
Built to withstand the high exhaust temperatures, pressure, and demanding conditions generated by the high-output M139 turbocharged engine. Precision-welded construction is designed to provide dependable performance for both street-performance and competition-oriented applications.
Direct-Fit Design:
Engineered specifically for compatible Mercedes-AMG A45 / CLA45 W177 M139 applications, providing a replacement for the factory downpipe configuration and designed to work with suitable OEM and aftermarket exhaust components.
Installation Hardware Included:
The downpipe includes the necessary clamps, bolts, and required installation hardware where applicable to help ensure a secure installation and proper sealing.
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 M139 engine to take full advantage of the increased exhaust flow while optimizing boost control, ignition timing, fueling, throttle response, and overall performance.
Estimated Performance Gain
Depending on the turbocharger configuration, ECU calibration, fuel quality, exhaust system, and supporting modifications, a properly tuned vehicle may see meaningful horsepower and torque gains from the reduced exhaust restriction.
For the Mercedes-AMG M139 2.0T platform, the largest gains are generally achieved when the downpipe is combined with an appropriate Stage 2 / downpipe-specific ECU calibration designed to take advantage of the increased exhaust flow. The ECU calibration may also require rear-O2 / catalyst monitoring to be disabled following removal of the factory catalytic converter.
| Configuration | Estimated HP Gain | Estimated Output |
|---|---|---|
| Stock Tune | ~5–12 HP | ~421–428 HP* |
| Stage 1 Tune | ~40–60 HP | ~456–476 HP* |
| Stage 2 / Downpipe-Specific Tune | ~60–80 HP+ | ~476–496 HP* |
Figures are estimated crank horsepower based on a 416 HP A45 S / CLA45 S reference, 91–93 octane (95–98 RON) pump fuel, and stock turbocharger hardware. Actual results will vary depending on the specific vehicle, factory power rating, ECU calibration, fuel quality, engine condition, supporting modifications, and dyno methodology.
Note: US-market CLA45 non-S models are rated at approximately 382 HP, so estimated absolute output will differ from the 416 HP reference configuration.
⚠️ Check Engine Light Warning
A Check Engine Light (CEL) is expected after installing a catless downpipe with the factory ECU calibration due to the removal of the factory catalytic converter and the resulting change in exhaust emissions readings.
A compatible ECU tune is strongly recommended and may be required to properly calibrate the vehicle after installation and address catalyst-efficiency-related fault codes.
A downpipe-specific Stage 2 calibration may require rear-O2 / catalyst monitoring to be disabled for proper operation following removal of the factory catalytic converter.
Tune requirements can vary depending on model year, ECU software, emissions equipment, and existing modifications.
For optimal performance, drivability, and compatibility, professional ECU tuning is recommended.
Why Upgrade?
The factory downpipe and catalytic converter configuration is designed primarily around emissions control, noise requirements, and factory operating specifications. These components can create additional restriction in the exhaust system, particularly as engine airflow and boost pressure increase.
The Untd. Performance Catless Downpipe provides a significantly freer-flowing exhaust path from the turbocharger, helping reduce exhaust backpressure and improve exhaust gas evacuation.
On a stock vehicle, the factory ECU may only realize a modest increase in performance because the calibration is not designed to fully utilize the additional exhaust flow. When combined with an appropriate ECU tune, the downpipe can provide a strong supporting modification for extracting additional performance from the Mercedes-AMG M139 2.0T.
Compatibility
- Mercedes-AMG A45 S – W177 – M139 2.0T
- Mercedes-AMG CLA45 S – C118 / W177 Platform – M139 2.0T
- Mercedes-AMG A45 – W177 – M139 2.0T
- Mercedes-AMG CLA45 – M139 2.0T
- 2019+ Mercedes-AMG M139 2.0T Applications
- A45 S – 416 HP
- CLA45 S – 416 HP
- US-Spec CLA45 non-S – 382 HP
Fitment may vary depending on model year, engine code, drivetrain, transmission, ECU software, emissions equipment, and existing exhaust modifications. Please verify compatibility before ordering.
⚠️ Important Notice
CATLESS / OFF-ROAD USE ONLY: This product eliminates the factory catalytic converter and may not be legal for use on public roads in your jurisdiction. Check your local emissions, inspection, and vehicle regulations before installation.
A Check Engine Light may occur without appropriate ECU calibration. A compatible tune may be required for proper operation and optimal performance.
PERFORMANCE GAINS ARE ESTIMATES: Actual horsepower and torque gains will vary depending on turbocharger configuration, ECU calibration, fuel quality, supporting modifications, engine condition, and dyno conditions.
Professional installation and ECU calibration are recommended.
Untd. Performance is not responsible for emissions compliance, inspection requirements, or the legality of installing or operating this product on public roads.
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