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Catalyst / Bypass

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Special Order item
90015100703
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Product Information
Heatshield Locking Bolt washer 7,4mm . EACH.

porsche

Fits:
Porsche Boxster 986

Click 'Zoom in' for large parts diagram.
Diagram ref no 26

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90015100703
90015100703
90015100702

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99611302
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Standard Replacement Exhaust Catalytic Converter for Porsche Boxster 986 2.7L / 3.2L 400 Cell

PORSCHE BOXSTER 2.7L & 3.2L S Replacement Type Approved Petrol Cats made in grade 409 stainless steel. Recommend to change in a pair

Fits:
Porsche Boxster 986 2.7L / 3.2L
Note: You will need M8x1x10 Plug (9000838000) & M8x11.5 Seal ring (90012305020) from each original Cat or suitable replacement


A catalytic converter is an emissions control device to stop harmful exhaust gasses from entering the atmosphere. In 1993, they became legality in the UK as part of the Euro Emissions standards. The aim of them is to improve air quality. As emissions standards have become more stringent the number of cats on a vehicle has increased. Many vehicles now have two or more to enable them to meet the Euro Emissions standards.

Our cat is made up of the following components:
• Ceramic monolith of a honeycomb design to allow free air flow and maximum surface area, coated with precious metals to enable the conversion of gasses that pass through it
• Interam matting to hold the monolith in place. The matting expands when exposed to heat to supply the pressure needed to keep the monolith secure
• A grade 409 stainless steel can (or housing) to provide protection and enable the cat to be built into the exhaust system. 409 grade can contain upto 90% iron and will be prone to rust. It still has higher rust-resistant properties than mild steel.



Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99611302
99611302111
996113021AX
99611302112
99611302502
996113025AX
99611302503
99611302504
996113025BX
99611302211
99611302212
996113022AX
99611302602
99611302603
996113026AX
99611302604
996113026BX

The product you are viewing cross references to these numbers
99611392
Product Information
Product Information
Standard Replacement Exhaust Catalytic Converter for Porsche Boxster 986 2.5L

designtek

Porsche Boxster 2.5L Replacement Cats made in grade 409 stainless steel. Recommend to change in a pair

Fits:
Porsche Boxster 986 2.5L

Note: You will need M8x1x10 Plug (90021901500) & M8x11.5 Seal ring (90012305020) from each original Cat or suitable replacement



A catalytic converter is an emissions control device to stop harmful exhaust gasses from entering the atmosphere. In 1993, they became legality in the UK as part of the Euro Emissions standards. The aim of them is to improve air quality. As emissions standards have become more stringent the number of cats on a vehicle has increased. Many vehicles now have two or more to enable them to meet the Euro Emissions standards.

Our cat is made up of the following components:
  • Ceramic monolith of a honeycomb design to allow free air flow and maximum surface area, coated with precious metals to enable the conversion of gasses that pass through it
  • Interam matting to hold the monolith in place. The matting expands when exposed to heat to supply the pressure needed to keep the monolith secure
  • A grade 409 stainless steel can (or housing) to provide protection and enable the cat to be built into the exhaust system. 409 grade can contain upto 90% iron and will be prone to rust. It still has higher rust-resistant properties than mild steel.


Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99611392
99611392101
99611392201
996113921AX
996113922AX

The product you are viewing cross references to these numbers
Special Order item
99950741308
Product Information
Product Information
Retaining clip Speed nut. EACH.

porsche

Fits:
Porsche Boxster 986

Diagram ref no 25

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

99950741308
99611342200
99611342100
99950741308
99950741309

The product you are viewing cross references to these numbers
DISPLAYING 17 to 20 (of 20 products)
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About Catalyst / Bypass

Exhaust Catalytic Converters & Bypass Pipes – Performance, Efficiency & Flow Control

The catalytic converter plays a crucial role in your Porsche’s exhaust system, reducing harmful emissions while maintaining optimal exhaust flow. Positioned between the exhaust manifold and silencer, it converts toxic gases such as carbon monoxide, hydrocarbons, and nitrogen oxides into less harmful emissions before they exit the tailpipe.

At Design911, we offer a complete range of catalytic converters and bypass pipes for Porsche vehicles. Our manufacturer-quality converters ensure reliable emission control and long-term performance, while our bypass options are designed for track or performance use, optimising exhaust flow for maximum power and throttle response.

Whether you’re maintaining your Porsche to meet emissions standards or upgrading for improved exhaust performance, our selection includes both direct-fit converters and performance bypass kits built from high-grade stainless steel for strength, corrosion resistance, and durability.

What Do Catalytic Converters & Bypass Pipes Do?

A catalytic converter uses a fine mesh of precious metals to trigger chemical reactions that break down pollutants. The bypass alternative eliminates restriction in the exhaust flow, improving performance in non-emissions-controlled environments such as track driving.

Core Functions:

  • Converts toxic exhaust gases into environmentally friendly emissions.
  • Maintains exhaust back pressure for engine efficiency.
  • Reduces harmful NOx, CO, and HC emissions.
  • Supports smoother engine performance and throttle control.
  • Bypass versions enhance exhaust flow and improve power output for track cars.

Upgrading to a performance-grade system ensures your Porsche continues to meet emission requirements — or achieves greater flow and responsiveness for motorsport applications.

Why Do Catalytic Converters Fail?

Catalytic converters are exposed to extreme heat, unburnt fuel, and contaminants — all of which can degrade their performance over time.

Common Causes of Failure Include:

  • Carbon or oil buildup blocking the internal honeycomb.
  • Thermal damage from overheating or rich fuel mixtures.
  • Physical damage from road debris or misfiring engines.
  • Corrosion due to moisture and exhaust condensation.
  • Age-related wear reducing catalytic efficiency.

A failing converter can cause reduced engine power, poor fuel economy, rattling sounds, or a check-engine light. Replacing it restores emissions compliance, performance, and exhaust efficiency.

Why Replace or Upgrade with Precision-Engineered Components?

Replacing a failing converter or upgrading to a bypass pipe ensures your Porsche maintains peak performance and reliability.

Key Benefits:

  • Restores optimal emissions performance and efficiency.
  • Improves exhaust flow and throttle response.
  • Reduces engine stress and fuel consumption.
  • Durable stainless-steel construction for longevity.
  • Direct-fit compatibility for Porsche 911, Cayman, Boxster, Panamera, Macan and more.
  • Performance bypass options available for track and tuning applications.

Whether you want emissions compliance or maximum flow for competition use, our parts deliver reliability, precision, and performance.

Highlights:

  • Direct-fit catalytic converters and bypass pipes for Porsche models.
  • Precision-engineered for optimal flow and reduced emissions.
  • Built from heat-resistant stainless steel for durability.
  • Bypass pipes for performance tuning and track applications.
  • Restores power, efficiency, and exhaust sound balance.
  • Available for classic and modern Porsche vehicles.

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