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For those of you that don't know me, my name is Matt Moreman. I’m going to maintain this thread with my exhaust One of the very first things I chased when I got my 991.1 GT3 back in 2014 was to figure out how to make the exhaust note better. I hate those darn valves, so I chased that really hard trying 15 or so different exhaust configurations. I can't stand the open at idle, closed at take-off, reopening at 3700, and closing again at the next gear shift. Now here we are with the GT4. This sucker has an added issue on top of having the same valve operation that the GT3 has, much longer gearing. Now, I don't mind the gearing of the car for the type of driving I do, but it makes the valve operation even worse as they still open at the same 3700 RPM. Unlike the GT3 that blows through that much quicker and on every shift, the GT4 moves around with valves closed much more often than not.
Since we are early into the 718 generation, we don't have a ton of choice, but what I've seen online Soul had the most promising stuff. I sent them an email asked what all they had been working on for the car. John Gaydos explained what they have learned about the car thus far and the options they have now. I posed the idea that I buy all the variants and test them out. Right now they have:
Future:
6.) Over-Axle Pipes and Valved Rear Section
7.) Over-Axle Pipes w/ Valve Controller
8.) Over-Axle Pipes with Catted Street Headers and Valve Controller
So here we go. First up is the adding the Over-Axle Pipes. In my normal fashion of documenting, I’m going to take a ton of photos and make overly long videos, but that’s just how I like to do it. I hope you will find this useful.
Since becoming a Milwaukee dealer, I've been able to play with every tool they make. This is my favorite one by a long shot. The High-Torque extended anvil is the most used tool in my cabinet.
First think is to remove the 3 nuts that connect the header to the over-axle pipe.
You can see the giant bung that houses the particulate filter. Some commenters on the video told me OPF stands for Otto Particulate Filter.
There are 5 bolts and studs that need to be removed. You have to back out the studs using the double nut method so that you don't have to remove the entire rear section. One of mine was either cross threaded from the factory and snapped off. I ended up cutting it off.
On the passenger's side I decided to get a little smarter and lubricated the bolts.
We reuse the gaskets.
It's tight, but the over-axle pipe comes out. I used a pry bar to get it off the studs on the header side.
Fit is spot on.
I'm not a big logo guy on my cars, but that Soul positioning is pretty darn cool.
I didn't know this, but the US cars have the filters, they just don't have a sensor.
I love my Sonic torque wrenches too.
The change is pretty significant, but as I mentioned in the initial paragraph, the factory valve operation kills it. I disconnected the valves afterward. That's the way to go. This car doesn't drone like the GT3 does. Next up will be adding the valve controller so that I will have the option to go back to factory operation should I desire.
Nice post matt and fantastic documentation. Enjoyed watching your youtube video.
I am eagerly awaiting my resonated race exhaust (from current stock setup).
We have realy similar cars except I have black wheels. As of now I have exact same exhaust setup (SOUL OAP and valves disconnected) and I really like the improvement so far. I'm waiting for the silenced race pipes from JCR and when I do the install I'll also add the SOUL valve controller to be able to keep valves closed (rarely I believe). It will probably be it for me exhaust wise but I will look forward to your impressions once you add the headers!
Next up is RSNV risers installation (in garage but lacking time to tackle the install). Your video will turn out handy I'm sure, but the install instructions are quite impressive!
Oh and I also had difficulty with 2 studs that didn't back out with double nut method, so I loosened the exhaust (keeping the 2 "hanger" bolts) and was able to remove the GPF without cutting/grinding. It might be the easier/faster option for others who will do the install, just a couple of bolts to undo then you can pivot exhaust out of the way.
Thanks Matt! Youre gonna be installing exhausts like a ****, and im gonna watch every video IMO you make THE BEST exhaust videos with respect to capturing sound both inside and out. With extensive impressions on liveability, quality, and relative sound. Looking forward to it.
PS Youre totally gonna end up with the nastiest sounding exhaust that doesnt give you a headache
hmmmm....that's strange. No commercial self interest of course.
Also, I don't get why Soul don't wrap their over-axle pipes with heat shield. Porsche engineers are not stupid and they would do it for a reason (otherwise just an unecessary cost). Akra do it. Can't be difficult.
Last edited by Warwick Morris; 10-18-2020 at 08:33 AM.
hmmmm....that's strange. No commercial self interest of course.
Also, I don't get why Soul don't wrap their over-axle pipes with heat shield. Porsche engineers are not stupid and they would do it for a reason (otherwise just an unecessary cost). Akra do it. Can't be difficult.
The consensus of various exhaust suppliers is that once you remove the OPF there's no bottleneck in that section to cause things to heat up.....it's nice to have the shielding but not necessary.
Also, when you take out those canister the clearance of the pipe to the other suspensions parts is increased. Soul does offer the option to coat the OAP with ceramic coating designed to contain heat.
To me the area that gets heat soaked a lot and causes problems on the long run are the headers......those coils on the 981 took a beating even witht he 991 heat shields added.
I think I saw some kind of shields on the 718? Not sure but it would be nice to have those.
I’ve said it before and I’ll say it again, $1600 for two pieces of SS pipe and 4 flanges is a bit much. I could MAYBE understand if it were ceramic coated.
Thanks for the detail Matt. Have been watching your videos since 2015 when you were swapping out GT3 exhausts in your oversized two car garage. Still some of my favorite videos on YouTube and I still will go back and watch them to this day, or listen to them in the background. Exciting to see which exhaust combination you end up preferring.
10-17-2020, 09:56 PM
Money2536’s 718 GT4 Exhaust Pursuit
IMO you make THE BEST exhaust videos with respect to capturing sound both inside and out. With extensive impressions on liveability, quality, and relative sound. Looking forward to it. 
