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Hello Everyone,

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 Over Axle Pipes

These factory over axle pipes appear to have a faux OPF matrix completely unmonitored by the computer system, unlike the Euro spec cars with monitored OPF cores. These were the first to go, and as you can see and hear this is going to be one of the best returns on investment for sound and performance improvement with a single product replacement. Uncorking these over axle pipes makes much better use of the factory valved PSE muffler. It maintains a very reasonable, almost factory-like sound inside of the car with valves closed, and valves open it is quite transformed. Eliminating the restriction of the headers and over axle pipes and keeping the factory PSE on the 718 GT4 / Spyder will without a doubt be the golden ticket setup for this platform.






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.

PSE Programming

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.


-Mike Spock
Marketing Manager
 

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Big difference
 

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So quiet over here (the thread not the exhaust!😕), way more 718 4.0l chatter on Rennlist...

I am watching these products with interest, especially the over axels pipes and valved exhaust for my Spyder.

BTW, great primer and descriptions Mike!
 
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Discussion Starter #4
So quiet over here (the thread not the exhaust!😕), way more 718 4.0l chatter on Rennlist...

I am watching these products with interest, especially the over axels pipes and valved exhaust for my Spyder.

BTW, great primer and descriptions Mike!
Thank you! Rennlist is definitely the place to be for 718.


Here is an update for you guys on what we’ve been up to since starting this thread as we concentrate on the header and over axle pipe development to start.

Competition Over Axle Pipes
Below are a couple photos of our prototype set used in the video we posted. The thick gauge aluminum fixture has been finalized to prepare for production. The bend profiles are currently being 3D scanned to have the primary flow path piping bent into the profile, eliminating five welds on the driver side and four welds on the passenger side. At that point we will test fit the final production version, take professional photographs of the finished product, compare the weights between ours and factory, and release this as the first product available for the 718 GT4 platform in June.

Below is a photo of Porsche’s part numbers for these over axle pipes. Note there are three versions of these over axle pipes - not two - and all three use particulate filters. We know North American versions are all the same and unmonitored, while Europe has the monitored versions. We’re waiting on clarification on what the mystery third set is for the region and if there is any change in the design. The North American version from Porsche retails for $3288 per side, by the way. Huge shoutout to our friends at Suncoastparts.com for working with us on doing a deep dive on this!








Competition Headers

It is very tight on space with the underbody panel on this car and these constraints have made header development a challenge. We’re focusing our initial efforts on a set of competition headers as we don’t have to worry about incorporating a cat core. Below are photos of the prototype headers we have built and test fit. It is especially tight to the engine and underbody panel on the driver-side (left) and requires some additional revision to clear which we are working on as we speak. The first version of these headers - for those that are antsy to get a set - will have laser cut header flanges to the spec of our prototype. However, we are taking these header flanges a step further and have designed and 3D printed the flanges for these headers to be sent out and cast or CNC machined to eliminate three welds per side. These will take several months to receive back and will from that point be incorporated into the headers. Regardless of which set you receive, the laser cut vs cast flanges will have a negligible effect on performance and they will both come with our Lifetime Warranty for both street and track use. Realistically, the Competition Headers could be available in June.














-Mike
 

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Looking good, can't wat to see the finished products and pricing for the OPF delete pipes and valved exhaust system!
 

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Thanks John for staying on top of the development of these exhaust options. Look forward to seeing the progress in the coming weeks.
 

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Westcoaster - which will you have first the exhaust or the Spyder ??

I stopped at a Porsche dealer while I was in CT having work done on my new RX-8 because I had time to kill. Seeing a nice leftover Silver Cayman S on the lot. I told the salesperson that it had too many options on it. He said "you don't have to pay for them, make us an offer". The window was $68k, I offered 60k figuring there was no way a Porsche dealer would take less than MSRP. It just wasn't done in 2007. He came back about 20 minutes later and said - you have a deal. I was in shock. We then talked monthly payment which was at an also very low 1.9%. The monthly payment was near what I figured in my head. So the RX-8 was left at the dealer (not sure how I was getting it back home to NY) and I started home with the CS after they sent it out for a rush detailing.
I remember stopping at Farnbacker Loges race shop on the way home from the dealer and picking up GT3 LCA, whatever those other bars were called, a BMC filter and scheduling the install & corner balance. We are (I am) ridiculous, aren't we. Car nuts is a good name for us.
 

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Very cool development !!!!
Another EU potential customer here.
IMO it's important to replicate OEM heat-shielding.
 
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