Fabspeed Secondary Muffler Bypass Pipe. Porsche 964 Carrera (1989-1994)  ›  FSPOR964SMB

The Fabspeed Porsche 964 Carrera Secondary Muffler Bypass Pipe is a performance exhaust upgrade designed to improve exhaust flow, reduce rear-end weight and deliver a more aggressive air-cooled flat-six exhaust note on Porsche 911 Carrera (964) models manufactured between 1989 and 1994.

Fits:

• Porsche 964 (911) C2 1989-94
• Porsche 964 (911) C4 1989-94
• Porsche 964 (911) RS 3.6L 1991-94
• Porsche 964 (911) RS 3.8L 1991-94

Developed as a replacement for the original right-hand secondary muffler, this straight-through exhaust pipe eliminates the bulky factory silencer and provides a more direct route for exhaust gases to exit the vehicle.

The Porsche 964 Carrera is powered by an air-cooled flat-six engine renowned for its distinctive mechanical character and engaging driving experience. However, its original exhaust system was designed to balance engine performance with noise reduction and everyday refinement.

The factory secondary muffler plays an important role in reducing exhaust sound before the gases exit through the rear tailpipe. While effective at controlling noise, its internal silencing arrangement also adds weight and may contribute to exhaust flow restriction.

Fabspeed developed this bypass pipe as a lightweight alternative inspired by the exhaust arrangements used on Porsche Motorsport's 964 Carrera Cup racing cars.

Manufactured from high-quality T304L stainless steel, the pipe features a full 3-inch (76 mm) diameter, CNC mandrel-bent construction and precisely TIG-welded joints.

The straight-through configuration reduces the restriction associated with the factory secondary muffler, allowing the engine's exhaust note to become more prominent.

Replacing the heavy original right-hand muffler also removes weight from the rear corner of the vehicle, potentially benefiting weight distribution and reducing the mass carried behind the rear axle.

Fabspeed advertises a weight saving of approximately 25 lbs (11.4 kg), although its product specifications also contain a different weight figure. The precise saving should therefore be confirmed for the vehicle and component configuration.

The bypass pipe is designed to work with compatible Porsche 964-style original equipment rear exhaust arrangements and retains the existing catalytic converter where fitted.

What This Product Does:
The Fabspeed Secondary Muffler Bypass Pipe replaces the original right-hand rear silencer with a straight-through stainless steel exhaust section.

Its primary functions include:

• Bypasses the Factory Secondary Muffler: Eliminates the original right-hand rear silencer from the exhaust path.
• Improves Exhaust Flow: Provides a less restrictive route for exhaust gases through the rear exhaust section.
• Enhances Exhaust Sound: Produces a louder, sportier air-cooled flat-six exhaust note.
• Reduces Rear-End Weight: Removes the mass of the factory secondary muffler from the right-hand rear corner.
• Supports Engine Response: Reduced exhaust restriction may improve throttle response under suitable operating conditions.
• Maintains the Original Catalytic Converter: Replaces a downstream muffler rather than the factory emissions-control catalyst.
• Preserves Compatible Factory Connections: Uses the corresponding original Porsche mounting and sealing arrangement.
• Accommodates Original Exhaust Tips: Allows the factory right-hand tailpipe outlet to be retained.
• Supports Motorsport-Inspired Builds: Recreates the general concept of a Porsche Carrera Cup-style rear muffler bypass.
• Provides Durable Stainless Steel Construction: T304L stainless steel helps resist corrosion and prolonged exhaust heat exposure.
• Maintains Smooth Pipe Geometry: CNC mandrel bending helps preserve internal pipe diameter through bends.
• Allows Reversible Modification: The factory secondary muffler can be refitted if the original components and mounting hardware remain available.

However, a damaged or deteriorating factory secondary muffler may need repair or replacement.

Typical symptoms:

• Ticking, hissing or blowing noises.
• Unusual increases in exhaust volume.
• Black soot deposits around pipe connections.
• Exhaust odours around the rear of the vehicle.
• Noise that becomes more noticeable under acceleration.
• Heavy corrosion on the muffler housing.
• Rust around welded seams.
• Perforations or holes.
• Flaking or weakened metal.
• Damaged exhaust connection surfaces.

• Reduced Rear Weight: Replaces the heavy factory secondary muffler with lighter stainless steel pipework.
• More Aggressive Exhaust Sound: Enhances the character of the air-cooled Porsche engine.
• Improved Exhaust Flow: Removes the internal restrictions of the right-hand secondary silencer.
• Potentially Better Throttle Response: Reduced exhaust restriction may support quicker engine response.
• Motorsport-Inspired Design: Based on the secondary muffler bypass concept used on Porsche 964 Carrera Cup cars.
• 3-Inch Exhaust Diameter: Provides a direct-flow exhaust passage.
• T304L Stainless Steel: Offers corrosion resistance and high-temperature durability.
• CNC Mandrel-Bent Construction: Maintains consistent internal pipe dimensions.
• TIG-Welded Connections: Provides durable welded joints.
• Compatible with Factory Hardware: Reuses original Porsche clamps and sealing rings.
• Factory Tailpipe Compatibility: Allows the original right-hand exhaust tip to be retained.
• Optional Fabspeed Outlet Tip: Can be paired with a compatible 4.5-inch oval tip.
• Retains Catalytic Converter: Does not remove the factory catalyst when installed on the specified exhaust system.
• Reversible Installation: Allows refitting of the original secondary muffler.
• Fabspeed Lifetime Warranty: Covered by the manufacturer's stated warranty conditions.