For years there was an argument from Porsche enthusiasts that the Cayman platform was being held back to avoid overstepping the 911 in performance. The closed-top mid-engine sports car demonstrated immense potential to drivers and racers alike, and slowly but surely Porsche’s GT department began to dial it up.
The 981 Cayman GT4 was the first time Porsche built a serious flagship variant, embedded with DNA from both hardcore GT cars and motorsports. It was a transcendental success and proved exactly what so many people theorized: the Cayman can be a serious contender. The 718 generation carried this progress forward but rumors began to swirl about the most potent Cayman road car yet. A proper RS version was coming.
The 718 GT4 RS arrived loaded with the flat-six from the 992 GT3 and GT3 Cup, finally putting to bed the idea that a Cayman was subject to the 911’s superiority. Like RS models before and alongside it, the GT4 employs weight savings, suspension and aerodynamic improvements, and the PDK gearbox to achieve road and track performance that is above all else. But even after demonstrating that performance potential, we saw opportunities to improve the experience.
With its billing among the most highly-anticipated performance cars of the modern era, we were just as anxious as all its waiting owners to get our hands on one. At the start of 2023, the opportunity finally came to us to develop a full suite of exhaust upgrades, and an even more exciting opportunity came for us to order our own GT4 RS. More on that when it arrives!
First and foremost, we needed to evaluate the GT4 RS system and align it with the goals and expectations we had from our previous experience with the standard 718 GT4. Like the standard GT4, the GT4 RS features a trio of modular sections that we will address, starting with the headers, then over axle pipes, and finally the rear muffler.
The exhaust flow begins through headers with 2” primary tubing, which comes to a short 3-to-1 merge collector and then a relatively small primary catalytic converter. A sharp bend meets the factory over axle pipes and necessitates a casted end cap, increasing strength and durability and reducing weld points. Exhaust then exits through 2.5” internal tubing into the over axle pipes.
Like with the standard GT4, we started our development with the over axle pipes in order to maximize sound and power with just a single component replacement. But on the RS, size was a factor for both better and worse. To accommodate the increased demands of the GT4 RS’ 4.0-liter, tubing diameter for the factory pipes increased from 2 ¼” to about 3”, and downstream it leads into a large multi-chambered canister–a massive cork in the flow of sound and power. The chambers are built to house a monitored particulate filter in the first chamber on European cars, but this is left empty on North American market cars. The second chamber houses a dense and redundant cat core matrix just like the unmonitored OAPs on the standard 718 GT4.
The over axle pipes then meet the rear muffler via single 3” flanges instead of dual-flowpath flanges on the standard GT4 system. This is a welcome change over the standard GT4, allowing for more flexibility combining various exhaust components using the same single flowpath OAPs on both valved and non-valved muffler replacements.
The single flange meets the rear muffler, then a casted Y-section splits the flowpaths for valves open and closed, directing them through what we found to be the same muffler as the standard GT4. Like on the GT4, the muffler is designed for fitment around the rear diffuser, and the two flowpaths offer a choice of muffled cruising or a mostly unrestricted flat-six tone. However, the tubing diameter remains the same as the standard GT4 which means exhaust flow necks down to 2 ¼ inches with valves open and 1 ¾ inches with valves closed. For cars fitted with the Weissach Package and its signature titanium exhaust tips, this will restrict that tubing diameter to 2 ¼ inches and therefore our tips will provide the most unrestricted flow through the rear.
With our experience on the GT4 platform, we know we can optimize that rear section in both power and sound, and now the delta of change from our system on the RS will be greater than that on a standard GT4. But we’re beginning from the engine rearward, and will cover some of how we aimed to achieve it.
For headers on the 718 GT4, we developed both catted and catless options for those minding both sound and emissions concerns. For the RS, we opted not to make that compromise. There’s just not enough real estate for larger tubing and a merge collector to meet the 3” flowpath of the OAPs, and with the O2 sensor monitoring from the OAPs we can relocate the primary cat to that section for a catted solution. Our Street Over Axle Pipes will feature this solution, and a Street Package will include them with the headers.
The over axle pipes are next down the exhaust stream, and we feel will represent the greatest potential for sound with a single component change, specifically our Competition version. By eliminating the redundant secondary cat core along with the empty particulate filter canister, flow is significantly improved and our solution maintains full 3-inch diameter from flange to flange by using oval tubing to fit within the clearances of the car’s suspension and body. This is a unique and, we feel, necessary development to maximize the performance of the GT3-derived engine. Radiant temperatures are also better managed without the heat soaking of the factory unit, but as always we offer thermal solutions because it never hurts to do so!
For those who find the sound level and tone of the Competition version a bit much to handle, we offer a Resonated version to smooth out and limit the overall volume. And as mentioned above, a high-flow catted version is an option as well, either pairing with our Competition headers or still providing better flow than the factory pipes.
As we now reach the rear section of the exhaust, we see a familiar component but presenting a new challenge. Despite the increased power from the 4.0-liter flat-six, the inner tubing of the rear muffler is unchanged and therefore corks the airflow. All of our rear exhaust systems feature full 3” tubing straight through the tips, with the x-pipe delivering crisp motorsports tone and the entire system unleashing the proper potential of the GT3-derived engine. A Resonated version with anti-drone tubes makes a significant difference under 2500 RPM, while a full Valved exhaust with 3” oval tubing achieves the incredible character with minimal drone courtesy of the secondary flowpath. Paired with our Valve Controller Kit, it will deliver that signature tone throughout the rev range.
Whether sound or performance is the ultimate goal for your GT4 RS, we’ve designed our components to not sacrifice on any aspect of it.