Me and my brother installed a GHL 3" downpipe on his 1.8T last weekend and I snapped pictures along the way so I could do a little write up for all those wondering how it is done. It is a fairly easy procedure it just takes some time because some of the bolts are hard to get at or rusted. Here we go.
First of all you are going to need some basic tools. You need a jack and at least 2 jack stands, but I recommend 4. It is easiest to work on th ecar if the whole thing is up off the ground. You will need basic sockets and open end wrenches, a hammer or preferably a BFH (Big Freakin Hammer), and some zip ties. That is about it as far as tools.
Here is a shot of the engine bay
From here you want to look at the passanger side by the fire wall and you will see this.
That is the top of the downpipe and if you don't have a strut brace in you might be able to get at a bolt or 2 from the top side.
To start get the car jacked up and through it onto jack stands. I prefer to put all 4 corners up so you can crawl all over under the car. Now depending on your exhaust setup you may need to disconnect the whole thing or you may be able to leave it in place. With us and this Supersprint 2.5" cat back the couplet to the stock downpipe is very long and inorder to slide it off of the stock downpipe we needed to completely unbolt the exhaust.
Once the car is jacked up take this cross member with the exhaust hanger out.
Then loosen the exhaust and slide it off of the stock downpipe.
Next disconnect the down pipe from the turbo. Most of the bolts are easier to get to from the bottom of the car. I suggest taking a drop light and sticking it down from the top and shining it right on the bolts. Make sure you use plenty of penetrating lube. WD40 is not a very good penetrating lube you want something like CRC or liquid wrench, just get something that has penetrating lube written right on the front of the container. Lube these suckers up and tap on them a little to help the lube soak in. If you try wrenchig real hard on these when they are rusted (which they always are due to the extreme heat) you could break one. If you break an exhaust stud then you will be seriously screwed so take you time. We let them soak for about 15 minutes, but some let them soak for an hour or 2. They came off real easy with no struggle and the car has over 50,000 miles on it so it isn't brand new.
Here is a picture from under the car. As you can see there is plenty of room to get in there for these nuts.
Once you get it unbolted you have to manuever it out of the car. You may have to really hammer on the exhaust to get it off because it is usually crimped on from the ole exhaust clamp. Use the trusty BFH (no mechanic should be without one) and slam the hell out of the bracket that holds the exhaust to the crossmember hanger like it owes you money. Don't worry you wont bend or break that thing it should be welded on solid 1/2" rod and you can't swing that hard laying under a car in those awkward positions.
Unclip the wires that lead to the oxygen sensors so that you will have enough room to play with. We slid it just barely outside of the car and stepped on it and with an open end wrench unscrewed the oxygen sensors. We marked on of them with red electrical tape so that we knew which one went before and after the car on reinstallation.
Here are 2 pictures of the original factory downpipe and cat next to the 3" GHL downpipe and race cat. The GHL one is so big you can almost stuff you fist in it. You are going from a golf ball size to a tennis ball size.
Now installing the new pipe is reverse. thread the oxygen sensors in the correct order back into the new downpipe and bolt it back up to the turbo. I suggest using a new gasket. The shop we got the downpipe from said you coul duse the factory gasket a few times over, but when we got the old downpipe out the old gasket came out in 10 different pieces.
Here is a picture from the top of the GHL 3" downpipe installed on the car.
On the bottom side because the oxygen sensor placement is different on the GHL downpipe than it is on the factory one we used some zip ties to secure all the oxygen sensor wires to the clips that they didn't reach. Make sure they are up there real good and secure like this.
We reinstalled the Supersprint 2.5" catback exhaust and it is almost impossible to find a 3" to 2.5" exhaust reducer, but luckily GHL sells one. We ordered it from North American Motorsports and it cost another $25, but it is 304 stainless and we needed it. Now the whole exhaust system from the turbo to the exhaust tips is 304 stainless which is agood thing.
Put the reducer on, or a coupler if you have a 3" catback, loosly. Just get those hangers on. On my brother car the reducer did not want to go onto the 2.5" exhaust easily so we unbolted the mid pipe section and took it out of the car. I lined the reducer up with the midpipe and tapped it on with a hammer just to get it started. Then I took the whole midpipe and slammed that reducer on my wooden workbench a few times to drive it home with a vengence. It is times like these that make working on a car so much fun. Again the fitment issue is due to the fact that the exhaust was previously installed and the exhaust clamps that were used slightly crimped the exhaust distorting its shape enough to make this part a real PITA.
Now mate up the exhaust with the downpipe. The GHL reducer fits easily onto the downpipe you jsut have to wiggle everything around until you can move the exhaust back far enough to get a descent angle on the downpipe to get them together. The flex joint on the thing moves a good amount which makes this an easier job.
Here we had the exhaust hanging and were about to mate up the exhaust with teh reducer on the downpipe and that is when I realized that the reducer had to go onto the exhaust midpipe first then to the downpipe.
Once everything is together loosly you need to check that your exhaust tips are sitting straight and tha tall the piping is in its proper place, especially not that the section of the exhaust that goes over the rear axle beam is as far up there as it can get. Now that everything is lined up you can tighten everything back down. It is important to loose fit exhausts first, but the downpipe can be bolted tight to the turbo right away.
Now all that is left is to reinstall the crossmember with the exhaust hanger and you can drop the car and go for a cruise. You will notice the difference right away. Increased throttle response, a deeper tone, and that turbo spool up will really stick out.
Now you try.