WRX Info

Installing a Turbo-back Exhaust (TBE)

Bone stock the WRX is one of the best performing 25k cars you can find, but there's always room for improvement. Replacing the stock 2.25" exhaust and it's 2 catalytic converters with a 3" turbo-back exhaust, featuring one high flow cat, should allow the turbo to spool up easier and quicker for more low end grunt. Another benefit is the super quiet stock exhaust tone should be replaced with a more sporting tone. Along with these goals of performance and aural enhancement, we also wanted to keep the sleeper look our wagon bodied WRX affords. Lucky for us M2 Performance had just the ticket, a 3" turbo back exhaust with a dual tip muffler. M2 originally specialized in Mazda's only, but with the release of the WRX in the states, M2 has jumped into the WRX market with a vengeance and has already built up a good reputation within the Subaru community. The look of the M2 system is so close to stock that your local racer might not be able to tell the difference. For those of you who want a more obvious look, 4 and 5" single tip mufflers are also available.

Perform this installation at your own risk. We do not assume any responsibility whatsoever for any damages of any kind resulting from any information printed in this article. This article was created as a supplementary resource and should not be used as the lone source of information on this topic. We recommend that you seek the advice of a trained professional. This is simply a guide to show users how we accomplished our own installations for our Project Car.

A few tips for installation:
1. Make sure the vehicle has had sufficient time to cool down. We allowed our WRX to cool off for 3 hours with the hood up and it was still very warm to the touch!
2. Gather all tools you'll need before you begin.
3. Spray all bolts with a lubricant such as Liquid Wrench or WD40 and allow to penetrate for about an hour.
5. Use protective eye wear. Our tools consisted of a socket set, box end wrenches, an adjustable wrench, wire crimpers and some wire snips.

Parts Installed:

  • M2 3-inch Stainless Steel Turbo-Back Exhaust System

  •  Step 1:
    Remove the heatshield. You'll be amazed at the amount of bolts used to hold on this simple piece of metal. There are 5 on the left side (viewing from the front of the car), one on the back, and two on the right side. After you have all the bolts removed you're going to need some keen geometry skills to get the heat shield out of the engine bay but once you do, the downpipe to turbo connection is easily available. Once the downpipe is exposed look for the bottom heatshield. It connects to the downpipe by one bolt.

    Step 2:
    Loosen the downpipe. There are only 5 bolts holding the downpipe to the turbo. They are surprisingly easy to get to. Now would also be a good time to remove the O2 sensor from the Downpipe. Reference Step 5's picture for it's location.
    Step 3:
    Disconnect the remaining hangers. We've used photos of the exhaust out of the car in order to point out where the hangers are in relation to the whole system. Install the new Downpipe by lining up the turbo/ downpipe bolts then securing the hangers. There are 2 hangers for the downpipe shown here. The front one bolts into the tranny. The second rests on a J bracket and is screwed in.
    Step 4:
    Hooking up the Midpipe. This one is very easy. Simply use the gasket provided by M2 to join the downpipe to the midpipe. Then use the stock rubber hanger and presto!
    Step 5:
    With the Midpipe in place it's time to relocate the O2 sensor. This step is required since the M2 system has it's cat in the midpipe. Without the O2 sensor plugged in, you can expect to see a check engine light come on. We had to splice the O2 sensor to extend it the 12" or so required to reach the new bung, but have since learned that this step might be unnecessary due to some extra length of O2 wire tied up in the engine bay.
    Step 6:
    Hanging the muffler. Once again we used the stock rubber hangers with no problems. Once you have everything in place it's time to tighten it all down. Double check everything, start her up, and check for exhaust leaks. If everything looks ok, put the head shield back on. Note: Heatshield will require some modification. See step 9.

    Step 7:
    Here's a side-by-side comparison of the M2 and stock exhausts. As you can see the M2 has less bends, one less cat, a nice flex section to protect the exhaust, and way less restrictive downpipe to turbo connection.
    Step 8:
    Here's the O2 sensor spliced to extend to the Midpipe. As mentioned before this step may be unnecessary if you're able to stretch the factory wiring enough to reach the new location.

    Step 9:
    The heatshield required a little reworking in order to fit around the larger diameter downpipe.
    Step 10:
    This is what the M2 exhaust looks like fully installed. One minor sticking point is that our muffler seems to be slightly (1/2") off center. As you can see the system is tucked under the car very well and there is very little room left. This could be a contributing factor to the variance.

    The M2 3" Turbo-Back Exhaust fit our goal of keeping the stock look, only the polished finish gives it away with anything less then a close inspection. In terms of driving feel the WRX is really transformed. Low-end pull is significantly improved and bogging due to turbo lag is now non existent. M2 claims customers can expect up to a 15hp gain from the system and our finely tuned butt-dynos tell us that's just about right.