Description
Unlock increased exhaust flow from the latest-generation BMW B58 Gen2 3.0T inline-six with the Untd. Performance 4.5″ Catless Downpipe, designed specifically for the BMW M240i, M340i, M440i, and X5 40i xDrive platforms.
Featuring an oversized 4.5″ diameter, this downpipe significantly increases exhaust flow compared with the restrictive factory catalytic-converter assembly. Reducing exhaust backpressure allows the turbocharger to expel exhaust gases more efficiently, helping improve turbo response and supporting substantially higher power levels when combined with ECU tuning.
Key Features
- 4.5″ Large-Diameter Design: The oversized 4.5″ diameter provides exceptional exhaust flow capacity for high-output B58 Gen2 applications.
- Catless Design – Maximum Exhaust Flow: Eliminates the restrictive factory catalytic converter to dramatically reduce exhaust backpressure.
- Improved Turbo Response: Reduced backpressure can help the turbocharger spool more efficiently and improve overall response.
- Designed for B58 Gen2: Specifically developed for the latest-generation B58-powered BMW applications.
- High-Flow Performance: Provides the exhaust flow capacity required for increased boost and higher engine output.
- Aggressive B58 Sound: The catless configuration produces a louder, more aggressive exhaust note with increased turbocharger and exhaust character.
- Ideal for Tuned Builds: Designed to complement Stage 1, Stage 2, and higher-output B58 Gen2 setups.
- Direct-Fit Platform Design: Engineered around the specified G-series BMW chassis for a proper fit.
Estimated Performance Gain
On the factory ECU, the additional exhaust flow can reduce backpressure and provide a small improvement in turbo response, but the stock calibration will not fully utilize the increased flow capacity.
The largest performance gains come when the downpipe is combined with an appropriate ECU calibration.
| Configuration | Estimated HP Gain | Estimated Torque Gain | Estimated Output |
|---|---|---|---|
| Stock Tune | ~8–15 HP | ~8–15 lb-ft | ~390–397 HP |
| Stage 1 | ~65–85 HP | ~65–85 lb-ft | ~447–467 HP |
| Stage 2 | ~88–98 HP+ | ~88–98 lb-ft | ~470–480 HP+ |
Performance reference: B58 Gen2 Stage 2 calibrations can achieve substantial increases over factory output when paired with appropriate hardware and 93-octane fuel.
These figures are estimated crank horsepower based on 91–93 octane (95–98 RON) pump fuel and the factory turbocharger. Actual results will vary depending on ECU calibration, fuel quality, ambient conditions, vehicle configuration, and supporting modifications.
Stage 1 vs. Stage 2
Stage 1:
The downpipe can be installed with a Stage 1 calibration and can provide improved exhaust flow and turbocharger response. However, the Stage 1 calibration is not specifically optimized around the additional flow provided by the downpipe.
Stage 2:
A downpipe-specific Stage 2 ECU calibration allows the B58 Gen2 to take greater advantage of the reduced exhaust restriction. Increased boost, optimized ignition timing, and revised fueling strategies can produce significantly greater power.
For catless applications, the calibration must also address rear-O2 and catalyst-efficiency monitoring.
⚠️ Check Engine Light Warning
Removing the factory catalytic converter can trigger a Check Engine Light related to catalyst efficiency and rear-O2 sensor monitoring.
A compatible ECU calibration is strongly recommended when installing this downpipe. Depending on the software and local regulations, catalyst monitoring may need to be addressed within the calibration.
Why Upgrade?
The factory catalytic converter is designed to meet emissions requirements while maintaining acceptable performance for the stock vehicle. As boost and engine output increase, the factory exhaust restriction becomes increasingly significant.
The 4.5″ Untd. Performance Catless Downpipe provides a much larger exhaust path, allowing exhaust gases to exit the turbocharger with less restriction. This can improve turbocharger efficiency, response, and high-load airflow.
For tuned B58 Gen2 vehicles, the downpipe provides supporting hardware for extracting significantly more performance from the factory turbocharger.
Compatibility
BMW B58 Gen2 2019+ Applications:
- BMW M240i — G42
- BMW M340i — G20
- BMW M440i — G22
- BMW M440i Gran Coupe — G26
- BMW X5 xDrive40i — G05
Engine: BMW B58 Gen2 3.0L turbocharged inline-six.
Important: This product is specifically intended for the B58 Gen2 applications listed above. Verify your vehicle’s model year, engine configuration, and downpipe connection before ordering.
Recommended Supporting Modifications
For customers building a higher-output B58 Gen2 setup, the 4.5″ downpipe can be paired with:
- ECU Stage 1 / Stage 2 calibration
- Upgraded intercooler / charge-air cooling
- High-flow intake
- Upgraded charge pipe
- TCU / transmission calibration
- Upgraded turbocharger
- Additional supporting fuel and cooling modifications for higher-power builds
⚠️ Important Notice
CATLESS — OFF-ROAD / COMPETITION USE ONLY.
This product removes the factory catalytic converter and is intended for closed-course, off-road, and competition use only. It is not emissions-legal for use on public roads where emissions equipment is required.
A Check Engine Light may occur following installation due to catalyst-efficiency and rear-O2 monitoring.
Horsepower and torque figures are estimates based on crank horsepower, 91–93 octane (95–98 RON) pump fuel, and the factory turbocharger. Actual results vary depending on ECU calibration, fuel, environmental conditions, vehicle configuration, and supporting modifications.
Professional installation and appropriate ECU calibration are recommended.
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