Description
Designed for the Mercedes-AMG GLC63 and GLC63 S 4.0T M177 platforms, the Untd. Performance Catless Downpipe is an ideal upgrade for enthusiasts looking to improve turbocharger response, increase horsepower potential, and unleash a more aggressive version of the AMG twin-turbo V8 sound.
By removing the restrictive factory catalytic converters and providing a freer-flowing exhaust path from the turbochargers, the Untd. Performance Catless Downpipe helps reduce exhaust backpressure and allows the M177 engine to expel exhaust gases more efficiently.
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 turbochargers. Reduced exhaust restriction helps minimize backpressure and allows the M177 V8 to move exhaust gases more efficiently.
Improved Turbo Response & Performance:
The freer-flowing design allows the twin-turbocharged M177 engine to expel exhaust gases more efficiently. When paired with an appropriate ECU tune and supporting modifications, reduced restriction can help improve turbo response, throttle response, horsepower, and torque.
Aggressive AMG V8 Sound:
The catless design significantly enhances the character of the AMG 4.0T V8, producing a deeper, louder, and more aggressive exhaust tone. Turbocharger spool and exhaust notes become more pronounced under acceleration, giving the GLC63 a more aggressive performance character.
Durable Construction:
Built to withstand the high temperatures, exhaust pressure, and demanding conditions generated by the twin-turbocharged M177 engine. Precision-welded construction provides dependable performance for both street-performance and competition-oriented applications.
Direct-Fit Design:
Engineered specifically for compatible Mercedes-AMG GLC63 and GLC63 S M177 applications, providing a direct replacement for the factory downpipe configuration and designed to work with suitable OEM and aftermarket exhaust components.
Installation Hardware Included:
The downpipes include 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 catless downpipes. Proper calibration allows the M177 engine and turbochargers to take full advantage of the increased exhaust flow while optimizing boost control, fueling, ignition timing, throttle response, and overall performance.
Estimated Performance Gain
Depending on the ECU calibration, fuel quality, exhaust system, and supporting modifications, a properly tuned vehicle may see significant horsepower and torque gains from the reduced exhaust restriction.
For the Mercedes-AMG 4.0T M177 platform, the largest gains are expected when the catless downpipes are paired with a downpipe-specific Stage 2 ECU tune. The increased exhaust flow allows the twin-turbocharged engine to operate with less exhaust restriction and provides additional airflow capacity for higher-output applications.
| Tuning Level | Estimated HP Gain | Estimated Output |
|---|---|---|
| Stock Tune | ~10–20 HP | ~513–523 HP |
| Stage 1 Tune | ~90–110 HP | ~593–613 HP |
| Stage 2 / Downpipe-Specific Tune | ~130–160 HP | ~633–663 HP |
Figures are estimated crank horsepower based on 91–93 octane (95–98 RON) pump fuel and stock turbochargers. Actual results will vary depending on the specific vehicle, engine condition, ECU calibration, fuel quality, supporting modifications, and dyno methodology.
On the factory ECU, the primary benefit of the catless downpipes is reduced exhaust backpressure and potentially quicker turbocharger response. However, the stock calibration will not fully utilize the additional exhaust-flow capacity.
Stage 1: An ECU remap using the factory hardware can optimize boost, ignition timing, and air-fuel ratios. A downpipe is not required for the Stage 1 power figures.
Stage 2: Combining the Untd. Performance Catless Downpipes with a compatible downpipe-specific Stage 2 calibration provides the greatest performance potential from the options listed above. Depending on the tuning solution, rear-O2 / catalyst monitoring may need to be addressed following removal of the factory catalytic converters.
Published aftermarket testing and tuner figures on the M177 platform demonstrate substantial gains when ECU tuning is combined with upgraded downpipes. Actual results vary by vehicle configuration, base power level, fuel, and calibration.
The non-S GLC63, with its lower factory-rated output, may see different absolute and percentage gains compared with the GLC63 S.
⚠️ Check Engine Light Warning
A Check Engine Light (CEL) may occur after installing these catless downpipes due to the removal of the factory catalytic converters and the resulting change in exhaust emissions readings.
On this platform, an inappropriate or incomplete calibration may also result in reduced-power / protection mode behavior.
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.
Depending on the tuning solution, rear-O2 / catalyst monitoring may need to be addressed through the ECU calibration.
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 and factory operating requirements. These components can create additional restriction in the exhaust system, particularly as engine power and turbocharger airflow increase.
The Untd. Performance Catless Downpipe provides a significantly freer-flowing exhaust path from the M177’s twin turbochargers, helping reduce exhaust backpressure and improve exhaust gas evacuation.
When combined with an appropriate ECU tune and supporting modifications, the downpipes can provide an excellent foundation for extracting additional performance from the Mercedes-AMG 4.0T M177 twin-turbo V8.
Compatibility
- Mercedes-AMG GLC63 – 4.0T M177
- Mercedes-AMG GLC63 S – 4.0T M177
- Mercedes-AMG GLC63 – 2018+
- Mercedes-AMG GLC63 S – 2018+
- Mercedes-AMG 4.0T M177 Twin-Turbo V8 Applications
Fitment may vary depending on model year, market, engine version, drivetrain, transmission, emissions equipment, ECU software, and existing exhaust modifications. Please verify compatibility before ordering.
⚠️ Important Notice
CATLESS / OFF-ROAD / COMPETITION USE ONLY: This product eliminates the factory catalytic converters 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.
REDUCED-POWER MODE: On this platform, installing catless downpipes without an appropriate ECU calibration may potentially result in catalyst-related faults and reduced-power/protection mode behavior.
TUNE REQUIREMENT: A downpipe-specific Stage 2 ECU tune is recommended to take full advantage of the increased exhaust flow and available performance potential.
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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