Changing full exhaust on Subaru WRX-DIY

knn By knn, 21st Dec 2009 | Follow this author | RSS Feed
Posted in Wikinut>Guides>DIY>Maintenance

Here is step by step guide how to replace the factory exhaust set up on a Subaru WRX to another system (3" turbo back in this case), it involves lots of handy tips and shortcuts with tools


- HIGHLY recomended: impact wrench(torque gun)-makes the job so much easier
- set of universal/imperial spanners, mostly, 10, 12, 13,14(THE MOST) and 22(o2 sensor)
- set of universal/imperial sockets and a socket driver
- two car ramps and two jacks(make sure the jacks are stable) stands would be great to put the car on after its jacked up
- mechanics trolley, not neccesary but will make manouvering under the car a lot easier
- WD-40, CRC spray(for rubber)
- scissors or a saw for metal
- few flat head and crosshead (phillips) screwdrivers
- if i remember any more tools i'll make sure i add them in

Getting started

first of all it great if you have someone else to help out!!!
now... back the car onto the ramps
jack it up level with the ramps and hopefully rest on some stands, make sure its all stable before going under the car
to start off grab the WD-40 and soak the screws on the bracket holding the TMIC in place as well as the five screws around the heat shield, it makes it a lot easier to remove them after.
from there grab the CRC spray and soak up the rubber holding the muffler in place, there are three in total and one in the middle just before the dumpipe, you can use WD-40 as well but its not as effective IMO when it comes to rubber
start by freeing the muffler from the holding rubbers
then undo the bolts at DBE section, if you have one, if not go straight to the cat back and undo those bolts, this is where impact wrench comes in handy as some of those bolts can be huge PITAs to undo, be careful not to "round off" the bolts if you're using the spanners, this is rather easily done.

Removing all the parts (all socket sizes are in SI units)

after removing the cat back section its prolly the best to get onto taking off the intercooler...
start by removing the BOV, its the same for the factory as well as aftermarket(at least on GC8s) you'll need a flathead screwdriver, undo the clamp holding the hose on the TMIC, the clamp where the BOV is plumbed back and the small boost hose at the bottom of the BOV.
then undo two bolts on each side of the TMIC, i think they are size 12, undo the clamp holding the TMIC hose on the turbo as well as the clamps on Y-PIECE and from there the TMIC comes off easily(its a huge PITA to put back on though), also remove the left bracket thet supports the TMIC in order to be able to pull the heatshield out later on.the bolts holding it are VERY hard to remove so make sure to soak them up with WD-40 before getting on with it or if yo have a impact wrench you should be sweet.
there are five bolts in total on the heatshield, two on the right, one on the left at the bottom and two at the back on the dumpipe, they are all size 10, and can be quite tricky to acces.remove then and take the heatshield off.
from there grab the size 14 socket and remove the bolts connecting the dumpipe to the turbo(turbine) there are 5 of them too, plenty of WD-40 as well makes the job easier
now its time to go back under the car and undo the first bolt holding the dumpipe, i suggest beeing caeful with this one as as dejan managed to almost completely round it off and we had ad lot of trouble undoing it(had to get a impact wrench), there is another bolt just before the catalyc converter, both of these are size 14. then there is 1 or 2 screws(not too sure what they are there for..) they are on the piece of metal coming off the cat conv, they are cross head, and it might be just easier to undo them from above than from under the car.(dont forget to undo the o2 sensor with a 22 size spanner(a lot of people willl recomend you get anew one as well and put it in instead)) BUT BE CAREFUL- after this the dumpipe will drop if you're not holding it, and its quite heavy, good idea to get someone to hold it from underneath, and there you go, you've succesfully removed the entire OEM exhaust setup

Putting your new exhaust and other parts on

from there on its quite simple acctually, provided you've got the right 3" exhaust it should fit on perfect, except not all bolts will go back on, at least in my case.all 5 bolts connecting the dumpipe and the turbine MUST go back on to ensure its sealed properly. then out the o2 sensor back in and tighten it firmly.

you WILL need to cut the heatshield to put it back on(highly recomended), you only need to cut a small section which goes back towards the dumpipe and has two screws going into it, so you will no longer need those two. three screws will hold it in place but you may need to either bend or cut off a supporting piece of metal(to the right facing the turbo) as it can cause few dramas when putting the screws back in place, im my experience anyway

then its time to put the TMIC back on,make sure you secure the left bracket first. now this was a HUGE PITA for me and dejan and i felt like smashing it to pieces at some stage, it just need A LOT of wiggling around to get the plastic hose to pop back ont the turbo as it constantly keeps bending and causing only one side to start sliding on and you pretty much get stuck there. we used a long piece of rubber to wrap around the hose just before it bends towards the turbo and pulled, it takes a while and you'll prolly damn it to hell but eventually it sits back on. tighten the clamp as much as possible to prevent any air leak. use a flat head screwdriver to get the Y-piece hose to sit back on and tighten it good with the two clamps.
then you put back the bolts on the side on the TMIC, the ones going into the brackets. make sure not to loose the rubber gaskets too, they fall off rather easy.
after this put the BOV back on, rather simple job, boost hose back on, plumback clamp tightenned, hose on the TMIC tigtenned, and basically the job's done!!!make sure these hoses are secured tightly though otherwise they might come off(used to happen to me before!)


well thats about it...all i can remember anyway, hope i didnt bore ya, i tried to be as detailed as i can, hope it helps, cheers

yours truly :)


Diy, Exhaust, Gc8, Turbo-Back, Wrx

Meet the author

author avatar knn
Hey, i've either been really helpful and you're checking out my profile, or you're bored to death. Happy reading!

Share this page

moderator Chief Nut moderated this page.
If you have any complaints about this content, please let us know


Add a comment
Can't login?