Fabspeed RENNKRAFT™ Modular Street and Racing Headers with HJS Catalytic Converters (718 GT4)


Designed to Fit:

  • 2020+ Porsche Cayman GT4
  • 2020+ Porsche Cayman GTS / Boxster GTS / Boxster Spyder (4.0L Only)

Product Details

These modular racing headers are the perfect solution for any street driven 4.0 liter Cayman or Boxster. Fabspeed's modular design features a quick release V-band connector that allows the owner to easily swap between our German made HJS 200 cell cats and a cat bypass “straight pipes” for track use. Rennkraft, translated from German is “race power”. These unique racing headers offer true street and racetrack functionality in an innovative precision engineered package. 


Many have complained about the lack of sound with the new 718 4.0 Liter cars, these high flowing headers completely solve that issue. Equipped with our 200 cell cats, you will get a louder exhaust note with a much more raw sound. Higher frequency tones are more defined, and deceleration burbles are more robust and transparent. With the cat bypass pipes installed, you're in store for a sound much more akin to a 911 CUP car than a Porsche street car. The volume isn't overbearing, but the sound is very aggressive and race bred. It totally changes the character of the car. With the stock muffler in place, there is no drone what-so-ever, even with our Over Axle GPF Delete Pipes also installed.


After extensive dyno development we found that mid length headers made the most power across the entire power band. With no tune, compared to a stock car we gained 31 whp and 19 ft/lbs of TQ at 7400 RPM with Sport Cats and 33 whp and 24 ft/lbs of TQ at 7200 RPM with Cat Bypass Pipes installed. That's a gain of 33 HP and 36 HP, respectively, at the crank! Peak horsepower also increased from our baseline of 383 whp to 405 whp with our HJS catalytic converters and 409 whp with Cat Bypass Pipes. See our dyno graph above for more details.


  • Fits all Porsche 4.0L Cayman/Boxster GT4/GTS/Spyder vehicles 2020+
  •   Impressive dyno proven power gains of 31 whp and 19 ft/lbs of TQ with the Sport Cats and 33 whp and 24 ft/lbs of TQ with Cat Bypass installed
  • Save 2 lbs / 0.9 KGs with Sport Cats and 7 lbs / 3.2 KGs with Cat Bypass compared to the factory headers
  • Modular design that uses a V-band clamp so one can quickly swap between cats and cat bypass
  • Switching to cat-bypass for track events prevents catalytic converter degradation during all out competition racing abuse
  • F1 style high velocity merge collectors
  • Designed from 3D scans of the OEM headers so we can achieve perfect bolt-on fitment
  • We use German-made HJS HD tri-metallic 200-cell EURO 6 homologated catalytic converters for the best performance and reliability
  • Fabspeed is the exclusive North American & South American importer and distributor for HJS Emissions Technology with HJS warranty
  • We use the largest catalytic converters that will fit in the factory location for maximum flow
  • Flows 93% of a 2.5 in straight pipe
  • Will NOT cause a CEL (Check engine light), NO P420 or P430 codes, when Sport Cats are installed
  • No ECU tune required
  • NOT EPA or CARB Certified and not be used on street driven vehicles
  • More sports car sound
  • Will fit with any brand of aftermarket exhaust system designed to work with the factory headers
  • Built 100% in house at Fabspeed Motorsport USA in Fort Washington, PA
  • These are the very finest headers for the 718 4.0 liter cars and where developed in collaboration with HJS Emissions Technology
  • 25+ years of air-cooled and water-cooled Porsche experience went into our design for these hand-crafted headers
  • Constructed from CNC mandrel-bent T304L stainless steel
  • Simple DIY (Do-It-Yourself) bolt-on installation, no cutting or welding required
  • All Fabspeed performance products are backed by the Fabspeed Lifetime Warranty



          About Fabspeed

          For over 20 years, Fabspeed has been engineering and manufacturing the world's finest stainless steel high performance exhaust systems and components, air intake products, ECU tuning, and more, specifically-tailored for high-end sports cars and exotics. From Porsche to McLaren, our expertise is unmatched and it shows in everything that we do. Their dyno-proven performance products provide an exhilarating driving experience and are backed by a Limited Lifetime Warranty.

          Fabspeed strives to be a force of innovation within the industry; dedicated to maximum performance, excellent service, and true care and concern for the development of products and services for exotic car enthusiasts.