MAD FATBOY Primary Downpipes | BMW F90 M5 | F91/F92/F93 M8

MAD FATBOY Primary Downpipes

BMW F90 M5 | BMW F91/F92/F93 M8

Maximize exhaust flow and unlock a more aggressive sound with the MAD FATBOY Primary Downpipes. Designed with the largest practical piping diameter between the mounting flanges, these downpipes provide a high-flow upgrade for performance-focused S63-powered BMW builds.

Constructed from premium T304 stainless steel, each downpipe features smooth mandrel bends and non-restrictive transitions designed to reduce turbulence and backpressure. This supports quicker turbo response, improved throttle response, and increased horsepower and torque potential when paired with proper tuning.

Integrated flex sections allow for controlled movement within the exhaust system, while the direct bolt-on design connects to the factory exhaust without cutting or welding.

Product Features

• Premium T304 stainless-steel construction
• Oversized FATBOY high-flow design
• Largest practical piping diameter between flanges
• Smooth mandrel-bent tubing
• Non-restrictive exhaust transitions
• Integrated flex sections
• Helps reduce exhaust backpressure
• Supports quicker turbo spool
• Improved throttle-response potential
• More aggressive exhaust note
• Compatible with right-hand-drive and left-hand-drive vehicles
• Direct bolt-on installation
• No cutting or welding required
• Installation hardware and gaskets included
• Lifetime warranty against manufacturing defects and fitment issues
• 90-day return period

Performance Benefits

• Potential gains of up to 30 horsepower on factory turbochargers
• Additional power potential with upgraded turbochargers
• Increased exhaust-flow capacity
• Faster turbo response
• Improved horsepower and torque potential

Actual results depend on tuning, fuel quality, supporting modifications, vehicle condition, and testing method.

Vehicle Fitment

• BMW M5 (F90)
• BMW M8 Convertible (F91)
• BMW M8 Coupe (F92)
• BMW M8 Gran Coupe (F93)

Engine: S63 Twin-Turbo V8

Important Notes

• These primary downpipes may trigger a check-engine light.
• ECU tuning may be required.
• Removal of factory catalytic converters may violate emissions and road-use laws.
• Intended for off-road or competition use where legally permitted.
• Confirm exact vehicle and exhaust compatibility before ordering.

Availability

In Stock & Ready to Ship

Orders generally ship within 1–2 business days.

Installation

Professional installation and appropriate ECU tuning are strongly recommended. Uproar Customs does not provide installation instructions or technical support for self-installation.