Description
Designed for the Mercedes-AMG A45 and CLA45 C117 2.0T M133, the Untd. Performance 3.5″ Catless Downpipe is an ideal upgrade for enthusiasts looking to improve exhaust flow, reduce turbocharger backpressure, improve turbo response, increase horsepower potential, and unleash a more aggressive version of the AMG 2.0T sound.
Featuring a large 3.5-inch diameter, this downpipe provides a significantly freer-flowing exhaust path compared to the restrictive factory configuration. By removing the factory catalytic converter, the Untd. Performance downpipe helps the M133 turbocharged engine evacuate exhaust gases more efficiently and provides additional flow capacity for tuned applications.
Key Features
3.5″ Catless Design – Maximum Exhaust Flow:
The Untd. Performance 3.5-inch Catless Downpipe eliminates the restrictive factory catalytic converter and provides a substantially larger, freer-flowing exhaust path from the turbocharger. The increased diameter helps reduce exhaust backpressure and allows the M133 engine to move exhaust gases more efficiently.
Improved Turbo Response & Performance:
The high-flow 3.5″ design helps the turbocharged 2.0T engine evacuate exhaust gases more efficiently. Reduced restriction can help improve turbocharger response, throttle response, horsepower, and torque, particularly when paired with an appropriate ECU calibration.
Aggressive AMG 2.0T Sound:
The catless configuration significantly enhances the sound of the M133 engine, producing a deeper, louder, and more aggressive exhaust tone. Turbocharger spool and exhaust character become more pronounced under acceleration.
Large 3.5″ Diameter:
The oversized 3.5-inch exhaust diameter provides increased flow capacity compared to the factory downpipe, making it well suited for performance-oriented and tuned M133 applications.
Durable Construction:
Built to withstand the high exhaust temperatures, exhaust pressure, and demanding conditions generated by the high-output M133 turbocharged engine. Precision-welded construction is designed to provide dependable performance for both performance and competition applications.
Direct-Fit Design:
Engineered specifically for compatible Mercedes-AMG A45 and CLA45 C117 M133 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 M133 engine to take advantage of the increased exhaust flow while optimizing boost control, ignition timing, fueling, throttle response, and overall performance.
Estimated Performance Gain
Depending on the ECU calibration, fuel quality, exhaust system, turbocharger configuration, and supporting modifications, a properly tuned vehicle may see meaningful horsepower and torque gains from the reduced exhaust restriction and increased exhaust flow.
For the Mercedes-AMG M133 2.0T platform, the largest gains are generally achieved when the 3.5″ downpipe is combined with an appropriate Stage 2 / downpipe-specific ECU calibration designed to take advantage of the increased exhaust flow. The 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 | ~5–10 HP | ~380–385 HP* |
| Stage 1 Tune | ~50–70 HP | ~425–445 HP* |
| Stage 2 / Downpipe-Specific Tune | ~65–90 HP | ~440–465 HP* |
Figures are estimated crank horsepower based on a 375 HP CLA45 C117 reference configuration, 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.
For reference, published tuner figures for earlier M133 applications have reported substantial gains with ECU calibration, demonstrating the tuning potential of the platform.
⚠️ 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 are designed primarily around emissions control, noise requirements, and factory operating specifications. These components can create additional exhaust restriction, limiting exhaust flow as engine airflow and boost pressure increase.
The Untd. Performance 3.5″ Catless Downpipe replaces the restrictive factory configuration with a substantially larger and freer-flowing exhaust path from the turbocharger.
The combination of a 3.5-inch diameter and catless design provides increased exhaust flow capacity, helping reduce backpressure and improve exhaust gas evacuation. When combined with an appropriate ECU tune and supporting modifications, the downpipe can provide an effective foundation for extracting additional performance from the Mercedes-AMG M133 2.0T.
Compatibility
- Mercedes-AMG A45 – W176 – M133 2.0T
- Mercedes-AMG CLA45 – C117 – M133 2.0T
- Mercedes-AMG CLA45 – C117 – 2016+
- Mercedes-AMG A45 – M133 2.0T Applications
- Mercedes-AMG CLA45 – M133 2.0T Applications
- Mercedes-AMG 2.0T M133 Turbocharged Four-Cylinder
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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