Say hello to our new R&D project, the 718 GT4! There’s been a lot of talk over the last few months about this car and a lot of discontent with some popular YouTube videos comparing the 718 GT4 and 981 GT4. Let’s dive right into it. More photos and videos will be forthcoming as we progress with development. The new 718 GT4 (and Spyder) as shown here now has three modular exhaust sections compared to the previous 981 generation that had two. Starting at the front, we have the headers and primary cat assemblies. The exhaust then bolts to a set of over axle pipes with canisters at the end, which then connects to the factory valved muffler system
The Headers (Primary Cat Assemblies)
Some of the immediate low hanging fruit that pops out is a rather restrictive merge collector that essentially has all three primary tubes hitting a wall, at which point the exhaust flows into a cat core just as dense as they have been before on previous Boxster / Cayman generations. We’ll get a bit more in depth into this once we take a closer look at the headers this week and come up with some prototypes. We will be making a catless long tube competition header and street header utilizing HJS HD 200 cell cat cores. With the superb new rear aero improvements, clearance is TIGHT from the headers to the underbody panel, so we may have to get creative with this header/merge collector design.
The Rear Muffler Section
Yes, California and European owners we’re listening! For you Cali folks, until we confirm these over axle pipes don’t have a true emissions control device in them we realize this is the only piece of the exhaust you can “technically” replace while passing inspection / emissions as there are CARB visual certifications requiring factory only components, even though you have a 6 year grace period if I recall before you have to go in for that. For our European friends in particular, we know you can’t touch the over axle pipes due to the monitored particulate filters as there is no high flow aftermarket replacement for those units yet (people are working on it) so that leaves the headers and the rear system. This factory PSE muffler is pretty well designed, albeit pretty funky looking to clear the rear diffuser. With valves closed it significantly cuts down on sound through the muffler body and with valves open it essentially bypasses the entire muffler assembly (diagrams / photos / video on this soon). However, if you’re looking to stay emissions compliant in your area it’s the only piece that can go and so it shall. We intend on offering several different versions of muffler replacement on this car – something wild for those that just don’t care and want to drop as much weight as they can, and something valved to have a similar wild factor but the ability to tone it down and take the edge off the sound to fly under the radar. The space constraints with the diffuser will make this complicated, but we’re up for the challenge and will start playing with the rear exhaust configurations once we complete header and over axle pipe development.
The Exhaust Tips
Unlike all the previous Boxster/Cayman generation that had welded on tip assemblies, the 718 GT4/Spyder has bolt on tips…finally! This is going to be an easy project, and expect a flurry of different tip options from us soon to kick up the cosmetic appeal on the backside of the car.
This is where things get interesting. European sound restrictions have been getting more and more severe over the last decade or so. Every time a new GT car comes out from Porsche, the PSE programming becomes more and more invasive in controlling the sound level of the car on full throttle. As many of you I’m sure have experienced on your previous Porsches, even with the PSE button pushed the programming will override this and close the valves until you reach a higher rpm range. The 718 GT4 is no different, and in fact it’s worse. With the button pushed, the 991 GT3 I drove the other week would shut the valves on hard throttle and then reopen around 3500rpm. With the button pushed, this GT4 keeps the valves closed until about 5000rpm. Now more than ever, the most inexpensive mod on sound you can perform on a GT car is unhooking the vacuum lines from the valves and plugging the lines so you don’t have a vacuum leak. Especially when unrestricting the exhaust upstream it makes a huge difference. Take the over axle pipes for example, below is a video where I drove this GT4 with our prototype over axle cat delete pipes. There are two takeoff clips in that video, the first take off clip is with the vacuum lines pulled and the valves in the default open position. The second take off clip has a large truck in it, during this one the PSE button was pushed/active for that takeoff and you can hear the valves close and then open at about 5k rpm. Completely different sound experience.
Now, for those who still want valve control but don’t want the PSE programming to override your fun we have one option now and are working on a couple others. We have our universal valve controller kit that simply works off constant 12V power, vacuum, and ground and has been used with great success on all of our valved exhaust systems for Porsches over the years. On this car it would serve to override the PSE button so it will no longer function, and the key fobs with our kit control the valves 100% closed or open. You can also sync the signal of these key fobs to your garage door buttons of the HomeLink system, so you can use existing buttons in the car instead of the key fobs if you so choose.
A second option may be an ECU tune. I’ve spoken with Scott at Softronic, our dedicated Porsche tuner. Many of you know him as one of the most experienced in the industry specializing in Porsche tuning for over 30 years. PCA Club Racing uses Scott to check all the ECUs to make sure no one is cheating, he also tuned all the Cayman Interseries cars, winning GTB1 cars, etc etc. He intends to look into the PSE programming itself to see if he can reprogram the ECU to simply keep the valves open 100% of the time when you press the PSE button. Along with all of the other benefits of software tuning Scott offers – such as power – this would be adding icing to the cake. We’ll look into this option for GT3’s as well.
A third option is our friends over at DSC, those suspension tuning wizards you’ve all come to know and love for the DSC suspension modules to maximize the potential of Porsche’s PASM system. They have been working on an addition to the DSC module that allows you to have full control over programming your valves to do whatever you want when you want. We are keeping in touch with them closely moving forwards (as we are a DSC dealer!) and very much look forward to seeing how this turns out to play with improving the valve control and suspension on this new platform.
Stay tuned for our next post!
Contact us at firstname.lastname@example.org for early adopter info and details
Questions? Comments? Let us know!
– Mike Spock / Marketing Manager