A comparison between OEM Mk6 Golf catback (left) and OEM Mk6 GTI catback (right). The five suspension points are at exactly them same location, but the GTI exhaust lacks the resonator. Of course, the outlets are also different, so you'll need GTI's diffuser. (The bumper covers are the same.) To be more specific, you need the following parts:
- Rear spoiler x1 : 5K6807521H9B9
- Tow hook cover x1 : 5K6807441C9B9
- Torx screws x2: N90974701 (the GTI diffuser/rear spoiler has two more locations for screws)
- Exhaust sleeves/clamps x2: 1K0253141N (you can use the original one on the car - in that case you only need one)
- An aftermarket resonator
As suggested by several forum threads (e.g.,
this and
this), Magnaflow's 10415 resonator is a good fit for this task. I found its length just barely enough - I need to adjust the exhaust sleeves so all four ends have enough coverage on the pipes. Nevertheless, it shows no problem to me after a month and several hundred miles of driving.
The diameter of the pipe ends for both Golf and GTI catbacks are the same, around 60mm.
The outer diameter of the Magnaflow resonator is about 61mm. It's a little bit larger than both OEM exhaust pipes, and barely fit into the OEM exhaust sleeves.
Start by removing the old exhaust sleeve between the OEM resonator and the cat. My car had several winters in NY, so there is quite a bit rust on the sleeve. To make things worse, the screws are facing INTO the exhaust tunnel. I don't understand why Volkswagen does this, maybe to avoid potential damage to the screws and nuts from the road debris? But this surely makes removing the sleeve a PITA. I spent whole afternoon to fight with these two nuts. Eventually, I used a small enough wrench that can fit into the tunnel to give me right angle (most torque) on the nuts to remove them.
There are two cross members at the exhaust tunnel to strengthen the car body. The front one is just in front of the sleeve (partially shown in the photo above). This one is handy, because it can support the catalytic converter when the exhaust is removed. (Service manual warns the front side of the catalytic converter cannot be bent too much, otherwise it'll be damaged.) The rear one, however, got into the way when I tried to remove the exhaust, and needs to be removed.
Following photos shows four of the five suspension points. (The last one can be seen from the left rear wheel well and is similar to the one below.) This one is at the rear left of the muffler and can be seen behind the bumper:
These two are just behind the rear exhaust tunnel cross member:
I removed these rubber mounts by applying some silicone spray on them, inserting a small Philips driver between the exhaust mount and the rubber mount, and forcing it out. The last mount at the rear right of the muffler is a bit different, shown in the photo below (see the annotation on the image). For this one, I removed the two bolts fitting the mount to car body (torque 25Nm) instead of removing the rubber mount from the muffler. (You still need to pull it out once the old exhaust is removed and reuse it on the new exhaust, though.)
Now simply install the new exhaust. I didn't reuse the old clamp due to rust, and also I made the screws facing downward so it'll be easier to remove next time. Photo below shows the connection between Magnaflow resonator and the catalytic converter
... and with GTI exhaust. The torque specification for the clamp screws are 25Nm. Also remember to install the rear cross member of the exhaust tunnel. Torque them to 23Nm.
Video is recorded by GoPro HD Hero 2 with open back plate, attached to the rear bumper with suction cup. The sound of this exhaust setup is surprisingly mild: outside of the car, it sounds just like a OEM "performance-version" car: with a little bit more low frequency growl comparing to the OEM Mk6 Golf 2.5L exhaust. Inside the car, there is very little difference: it just get a tiny bit louder under load, and is most noticeable when around 2000-3000rpm. (The engine noise itself covers the exhaust noise with higher rpm.) However, the sound quality is good, and feels special, mostly because of the 5 cylinder engine. I also find the engine revs a bit smoother, and the additional sound feedback also helps me on take off and heel-toe.
In summary, I don't recommend this setup for people looking for exhaust sound: the gain is minimal. For untrained ear/eye, the car just sounds and looks like OEM. Only car enthusiasts would notice the slightly revealed growl created by the 5 cylinder NA engine - an increasingly rare breed among the modern 4 cylinder turbos. Nevertheless, it's better than OEM - Volkswagen should just make this the OEM setup, in my opinion.
