Description
Designed for the BMW M5 F90 and BMW M8 F91/F92/F93 equipped with the 4.4T S63TU4 V8, the Untd. Performance Catless Downpipe W/ Heat Shield – S63 Style 2 is an ideal upgrade for enthusiasts looking to reduce exhaust restriction, improve turbocharger response, increase horsepower and torque potential, and unleash a more aggressive version of the S63 V8 sound.
By removing the restrictive factory catalytic converters and providing a significantly freer-flowing exhaust path from the twin turbochargers, the Untd. Performance Catless Downpipes help reduce exhaust backpressure and allow the S63TU4 to evacuate exhaust gases more efficiently. The integrated heat shields also help manage radiant exhaust heat within the engine bay, making this setup well suited for high-performance and tuned applications.
Key Features
Catless Design – Maximum Exhaust Flow:
The Untd. Performance Catless Downpipes eliminate the restrictive factory catalytic converters, creating a significantly freer-flowing exhaust path from the twin turbochargers. Reduced exhaust restriction helps minimize backpressure and allows the S63TU4 to move exhaust gases more efficiently.
Integrated Heat Shield – Improved Heat Management:
The included heat shields help reduce radiant heat transfer from the high-temperature downpipes into the surrounding engine bay components. This helps provide additional thermal protection around nearby wiring, hoses, intake components, and other sensitive components while maintaining the high-flow benefits of the catless design.
Improved Turbo Response & Performance:
The freer-flowing design allows the twin-turbocharged 4.4T V8 to expel 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 S63 V8 Sound:
The catless design significantly enhances the character of the S63 V8, producing a deeper, louder, and more aggressive exhaust tone. Turbocharger spool and exhaust volume become more pronounced under acceleration.
S63 Style 2 Design:
Engineered specifically for the high-performance BMW S63TU4 4.4T V8, providing a high-flow replacement for the factory downpipe configuration while maintaining compatibility with suitable OEM and aftermarket exhaust components.
304 Stainless Steel Construction:
Constructed from 304 stainless steel for durability and resistance to the extreme temperatures and exhaust conditions generated by the twin-turbocharged S63TU4 engine.
Durable Performance Construction:
Precision-welded construction is designed to withstand the high exhaust temperatures, pressure, vibration, and demanding conditions associated with high-output BMW M applications.
Direct-Fit Design:
Designed for compatible BMW M5 F90 and M8 F91/F92/F93 applications, providing a replacement for the factory downpipe configuration.
Installation Hardware Included:
The downpipes include 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 catless downpipes. Proper calibration allows the S63TU4 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 ECU calibration, fuel quality, exhaust system, turbocharger configuration, and supporting modifications, a properly tuned vehicle may see significant horsepower and torque gains from the reduced exhaust restriction.
For the BMW S63TU4 4.4T platform, the largest gains are generally achieved when the catless downpipes are 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 converters.
| Configuration | Estimated HP Gain | Estimated Output |
|---|---|---|
| Stock Tune | ~10–20 HP | ~610–620 HP* |
| Stage 1 Tune | ~65–80 HP | ~665–680 HP* |
| Stage 2 / Downpipe-Specific Tune | ~90–110 HP+ | ~690–710 HP* |
Figures are estimated crank horsepower based on a 600 HP BMW M5 F90 reference configuration, 91–93 octane (95–98 RON) pump fuel, and stock turbochargers. Actual results will vary depending on the specific vehicle, factory power rating, ECU calibration, fuel quality, engine condition, supporting modifications, and dyno methodology.
BMW M5 Competition and BMW M8 applications with higher factory output may achieve similar absolute gains, resulting in different final horsepower figures.
⚠️ Check Engine Light Warning
A Check Engine Light (CEL) is expected after installing catless downpipes with the factory ECU calibration due to the removal of the factory catalytic converters and the resulting change in exhaust emissions readings.
On the S63TU4 platform, catalyst-efficiency faults can potentially be accompanied by a reduced-power / drivetrain protection mode depending on the vehicle’s ECU calibration and operating conditions.
A compatible ECU tune is strongly recommended and may be required to properly calibrate the vehicle after installation.
A downpipe-specific Stage 2 calibration may require rear-O2 / catalyst monitoring to be disabled for proper operation following removal of the factory catalytic converters.
For optimal performance, drivability, and compatibility, professional ECU tuning is recommended.
Why Upgrade?
The factory downpipes and catalytic converters are designed primarily around emissions control, noise requirements, and factory operating specifications. These components can create additional exhaust restriction, particularly as boost pressure and engine airflow increase.
The Untd. Performance Catless Downpipes W/ Heat Shields replace the restrictive factory configuration with a significantly freer-flowing exhaust path from the S63TU4’s twin turbochargers.
The integrated heat shields provide an additional layer of thermal management within the engine bay, helping reduce radiant heat exposure to surrounding components while maintaining the performance benefits of the catless downpipe design.
When combined with an appropriate ECU tune and supporting modifications, these downpipes provide a strong foundation for extracting additional performance from the BMW S63TU4 4.4T twin-turbocharged V8.
Compatibility
- BMW M5 F90 – 2017–2021 – S63TU4 4.4T
- BMW M5 Competition F90 – S63TU4
- BMW M8 F91 – S63TU4
- BMW M8 F92 – S63TU4
- BMW M8 F93 – S63TU4
- BMW M8 Competition – S63TU4
- BMW S63TU4 4.4T Twin-Turbo V8 Applications
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 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 and possible reduced-power mode 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.
Reviews
There are no reviews yet.