Description
Gain full potential of your Mercedes-AMG W205 C63 / C63 S 4.0L V8 Biturbo M177 with the Untd. Performance Catless Downpipe with Heat Shield. Designed to significantly reduce exhaust backpressure, this high-flow catless downpipe allows the M177’s twin-turbo V8 to evacuate exhaust gases more efficiently, helping improve turbocharger response, throttle response, exhaust flow, and overall performance.
By removing the restrictive factory catalytic converter, the Untd. Performance downpipe provides the increased exhaust-flow capacity needed for higher-power applications and Stage 2 ECU tuning. The result is a more responsive engine, stronger power delivery, and a significantly more aggressive AMG V8 exhaust note.
Key Features
Catless Design – Maximum Exhaust Flow
The catless construction removes the factory catalytic restriction, allowing exhaust gases to flow more freely and reducing backpressure. This is particularly beneficial on tuned M177 applications where increased airflow is required.
Improved Turbo Response & Performance
Reduced exhaust restriction can help the M177 turbos spool more efficiently and improve throttle response. The largest performance benefits are realized when paired with a downpipe-specific Stage 2 ECU calibration.
Aggressive AMG V8 Sound
Removing the factory catalytic restriction produces a noticeably louder, deeper, and more aggressive exhaust tone while allowing the characteristic M177 V8 sound to come through more clearly.
Heat Shield Included
The integrated heat shield helps protect surrounding components from excessive exhaust heat while maintaining a clean and performance-oriented installation.
Designed for High-Power Applications
The increased exhaust-flow capacity makes this downpipe well suited for vehicles running upgraded ECU calibrations and other supporting performance modifications.
Direct-Fit Design
Designed specifically for the Mercedes-AMG W205 C63/C63 S M177 platform for a straightforward installation using the factory mounting locations.
Installation Hardware Included
Includes the required installation hardware, including replacement gaskets, bolts, and related hardware where applicable.
Tune Strongly Recommended / Required for Stage 2
While the downpipe can physically be installed on a factory calibration, a tune is strongly recommended. For proper operation with a catless downpipe, a Stage 2 ECU calibration should address catalyst and rear-O2 monitoring.
Estimated Performance Gain
Actual results will vary depending on ECU calibration, fuel quality, supporting modifications, vehicle condition, and dyno methodology. The following figures are estimated for a C63 S W205 rated at approximately 503 HP, using the factory M177 turbochargers and 91–93 octane pump fuel.
| Tuning Level | Estimated HP Gain | Estimated Output | Estimated Torque Gain |
|---|---|---|---|
| Stock Tune | ~10–20 HP | ~513–523 HP | ~10–20 WTQ |
| Stage 1 Tune | ~90–110 HP | ~593–613 HP | ~80–110 WTQ |
| Stage 2 / Downpipe-Specific Tune | ~130–160 HP | ~633–663 HP | ~110–150 WTQ |
Stock Tune:
The factory ECU can benefit slightly from the reduction in exhaust backpressure, but the stock calibration will not fully utilize the additional exhaust-flow capacity. Expect approximately +10 to +20 HP and +10 to +20 WTQ. A check-engine light is expected.
Stage 1 Tune:
A Stage 1 ECU calibration can produce approximately +90 to +110 HP over the factory C63 S output, reaching approximately 593–613 HP. These figures are primarily attributed to the ECU calibration rather than the downpipe itself.
Stage 2 / Downpipe-Specific Tune:
With the Untd. Performance catless downpipe and a properly calibrated Stage 2 ECU tune, estimated output can reach approximately 633–663 HP, representing roughly +130 to +160 HP over the factory 503 HP rating. Estimated torque gains are approximately +110 to +150 WTQ.
The Stage 2 setup provides the largest performance potential because the ECU calibration is specifically designed to take advantage of the increased exhaust flow provided by the catless downpipe.
Performance figures are estimates only. Actual results will vary based on fuel, ECU calibration, supporting modifications, ambient conditions, dyno type, and vehicle condition.
Check Engine Light & ECU Tuning
Because this is a catless downpipe, removal of the factory catalytic converter changes the exhaust emissions characteristics monitored by the vehicle’s rear O2 sensors.
A check-engine light for catalyst efficiency / rear-O2 monitoring is expected when running the factory calibration.
On the M177 platform, a catless downpipe is strongly recommended to be paired with a properly calibrated Stage 2 ECU tune. The calibration should account for the increased exhaust flow and disable the appropriate rear-O2/catalyst monitoring strategies.
A reduced-power or protection mode may also occur if the ECU detects conditions outside its expected emissions and exhaust parameters.
Why Upgrade?
The factory C63 exhaust system is designed to balance performance, emissions compliance, noise, and comfort. For performance-focused builds, the factory catalytic restriction can limit exhaust flow as power levels increase.
The Untd. Performance catless downpipe addresses this restriction by providing a significantly freer-flowing exhaust path. Combined with an appropriate ECU calibration, it can help:
- Reduce exhaust backpressure
- Improve turbocharger response
- Improve throttle response
- Increase exhaust-flow capacity
- Support higher boost and power levels
- Produce a more aggressive AMG V8 exhaust note
- Improve the effectiveness of Stage 2 ECU tuning
For owners pursuing increased power from the M177 platform, the downpipe is an important supporting modification for a properly configured Stage 2 setup.
Compatibility
Mercedes-AMG C63 / C63 S W205
- Mercedes-AMG C63 W205
- Mercedes-AMG C63 S W205
- 4.0L V8 Biturbo M177
- C63 S – 503 HP factory rating
- Non-S C63 – approximately 469 HP factory rating
- W205 chassis
- M177 twin-turbo V8 platform
Important Notice
⚠️ CATLESS / OFF-ROAD / COMPETITION USE ONLY
This product removes the factory catalytic converter and is intended for off-road, competition, racing, or other applications where emissions regulations do not apply. It is not emissions-legal for use on public roads in many jurisdictions, including Canada and the United States.
A check-engine light is expected when running the catless downpipe without appropriate ECU calibration. A properly configured Stage 2 tune is strongly recommended for optimal performance and operation.
Professional installation and ECU calibration by a qualified performance specialist are recommended.
Estimated gains are not guaranteed and will vary depending on fuel, tune, supporting modifications, environmental conditions, dyno methodology, and vehicle condition.
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