DEVELOPMENT AND TESTING: We wanted to build an aggressive catted system that offers a modest increase in tone – including pops and burbles on deceleration – without triggering a check engine light. Support for high power was another consideration – necessitating 3″ tubing. We experimented with adding a mixing chamber into our X-pipe design. Analysis in 3D CAD software showed a general increase in velocity gained downstream of the mixing chamber across a band of measured pressure and temperature levels. This produces optimal flow characteristics, reduced backpressure for higher HP, and enhances the sound quality of the system. Quad race resonators make a discernible difference in reducing drone while encouraging a more refined exhaust note. We had modularity in mind – you can switch tips out, convert back to factory catalytic converters, or add our catless pipes at any time.
SOUND: The HJS catalytic converters flow extremely well, letting through more turbo and flat-six sound through. Quad resonators add a refined tone and cut down on droning in the cabin. The level of volume is perfect the owner looking for a sophisticated increase in sound – very aggressive on heavy throttle inputs while offering a mild and sporty presence during cruising.
CONSTRUCTION: Each Sport X-Pipe Exhaust System is made from mandrel bent T304L 3″ .065″ wall stainless steel tubing, straight through race resonators with a full metal packing design for maximum durability, and laser cut brackets for perfect fitment. Choose from several hand finished tip options to get the look that suits your 991 the best – or reuse your factory tips.
HJS CATALYSTS: The highest quality catalytic converters available, known for their industry leading flow and durability. They are efficient enough to meet strict EURO 4 emission standards while still allowing for an increase in flow – all without a check engine light. The HD design uses premium triple foil winding for maximum strength. The brazing stripe is an extra feature in the interest of durability – it prevents the core from moving or experiencing any damage from sustained high horsepower abuse. We use a large and appropriately sized catalyst to allow for maximum gains – no compromises here!
BOLT ON AND GO: Each exhaust is tested in a fixture to ensure perfect fitment then foam packed to ensure it arrives in perfect condition. Thorough installation instructions are included in the box for a straightforward install that can be performed by most DIY enthusiasts.
