When it comes to tuning high-performance BMW models, downpipes play a critical role in unlocking horsepower, torque, and engine response. Whether you drive the all-new BMW M5 G90/G99 or the aggressive BMW M3 G80, installing aftermarket downpipes—especially secondary or catless versions—can dramatically enhance your car’s performance and auditory experience. In this guide, we’ll explore everything you need to know about upgrading your downpipes for both models.
What Are Downpipes and Why Upgrade Them?
Downpipes are part of the exhaust system, connecting the turbocharger to the mid-pipe. They carry hot exhaust gases away from the turbo and help reduce backpressure. OEM downpipes, especially in modern BMWs, come with catalytic converters that restrict flow to meet emissions standards.
Upgrading to aftermarket downpipes—either catted (with high-flow catalytic converters) or catless (no converters)—can:
- Improve exhaust flow
- Increase horsepower and torque
- Sharpen turbo response
- Create a deeper, sportier exhaust note
- Prepare your car for ECU tuning and Stage 2+ power levels
BMW M5 G90/G99 Secondary Downpipes: More Power, Less Restriction
The G90 (sedan) and G99 (Touring) BMW M5 models are the latest beasts from BMW M GmbH, featuring hybrid twin-turbocharged V8 powertrains. These cars come with primary and secondary catalytic converters, meaning there’s more room to improve performance via upgraded bmw m5 g90 g99 secondary downpipes.
Secondary downpipes are easier to replace and often don’t affect emissions testing as significantly as primary cat deletes. Benefits of upgrading include:
- Improved flow without removing primary catalytic converters
- More aggressive exhaust tone
- Slight horsepower and torque gains (5–15 HP with no tune)
- Enhanced performance when paired with an ECU remap or piggyback system
Many aftermarket options offer stainless steel construction, heat shielding, and perfect fitment with OEM or aftermarket exhaust systems. Some popular brands include Active Autowerke, ARMYTRIX, and Eventuri.
BMW M3 G80 Downpipes: A Tuner’s Dream
The G80 M3 is one of the most tunable M cars in recent years. With its S58 twin-turbo inline-6, the G80 responds well to bolt-ons and tuning. One of the first upgrades any enthusiast considers is replacing the factory downpipes.
bmw m3 g80 downpipes are available in several configurations:
- Catless downpipes – Maximum flow and power gains but may trigger CEL and fail emissions
- High-flow catted downpipes – Better than stock flow with some emissions compliance
- Resonated/caged options – Reduce rasp or drone for daily drivability
Power gains with catless downpipes and a tune can exceed 40–60 HP at the wheels, making it a no-brainer mod for performance junkies. They also allow the turbos to spool faster and reduce heat buildup—perfect for track use.
Just keep in mind that some downpipes will require an ECU tune to remove CEL or adapt fueling and boost.
Legal Considerations and CEL Warning
Always check your local laws regarding emissions. In many regions (especially in the U.S., U.K., and Europe), removing or modifying catalytic converters is illegal for road use. If you’re planning to go fully catless, it’s best to keep your OEM parts in case you need to revert for inspection.
Also, unless you’re using downpipes with high-flow cats and built-in O2 sensor spacers, you’ll likely trigger a Check Engine Light (CEL). Some aftermarket solutions offer CEL-delete simulators, but the most reliable solution is ECU tuning via a reputable tuner.
Final Thoughts
Whether you’re aiming for modest gains with BMW M5 G90 G99 secondary downpipes or chasing maximum output with BMW M3 G80 downpipes, both upgrades offer solid performance improvements and a thrilling sound enhancement. They’re also great foundational mods if you’re building toward a full Stage 2 or Stage 3 setup.