As previously mentioned, the Porsche GT4 RS features a top-mounted throttle body that leads to the plenum, runners, and ultimately into the engine cylinders. In contrast, all other 6-cylinder 981 and 718 Cayman models have a rear-facing throttle body, which aligns with their original air routing. These models scoop air from the side vents behind the doors, directing it rearward before making a forward-facing turn toward the throttle body. Given our desire to retain the original throttle body and Y pipe, along with their respective positions, we undertook a complete redesign of the central portion of the intake system to accommodate this specific requirement.
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This design choice was driven by the wide array of aftermarket plenums, runners, and throttle bodies available on the market. Our redesigned system can seamlessly function with these existing components, eliminating the need for additional parts to be included with our system (e.g., the GT4 RS throttle body and plenum). Customers also have the option to revert to the original GT4 RS system, although it is notably more expensive.
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The redesign focuses on the intake system's central section, where incoming air enters the front bottom part of the system (referred to as the bottom dirty chamber). It then passes through the air filters, transitioning into the top clean chamber before entering the trumpets located at the rear of the system. Air flows through these trumpets, subsequently passing through the stock Y pipe and throttle body before entering the original plenum.
To make this configuration work seamlessly, the central system is constructed from four distinct parts. The upper skin part and upper structural part form the clean chamber, while the bottom structural part and bottom heat shield part create the dirty chamber. The upper two parts are bonded together, as are the bottom two parts. These two assemblies are then bolted together, creating an airtight seal while securely holding the air filters and connecting ducts in place.
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When selecting the air filters, we prioritized three key criteria. Firstly, the filters needed to be readily available worldwide on short notice. Secondly, they should be off-the-shelf filters, not custom-made, and ideally, they should have a larger surface area than the stock filters while fitting within the system's dimensions.
Fortunately, we identified suitable filters in the form of K&N 33-2304, which are also used in multiple Subaru models. These filters offer a greater surface area than the stock air filters in the GT4 RS, resulting in lower pressure drop and reduced restriction.
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Significant attention was devoted to water management and drainage within the system's design. The system is engineered to ensure that water droplets entering the dirty chamber are effectively drained through the bottom heat shield piece, with drainage points strategically positioned away from the engine and other critical components.
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The trumpets are inserted through the bottom assembly and securely held in place using plastic inserts and rubber O-rings, ultimately connecting to the stock Y pipe at the bottom.
