BMW 3-Series (E36) 1992-1999. Eddie Nakato

      All aftermarket exhausts fall into the same general envelope of performance enhancement; there’s only so much power you can get out of a cat-back. If you go with a well-known and respected brand, you have a good unit that installs easily with the stock hangers. Custom exhaust systems with weld-in mufflers, such as Flowmaster, generally require more work to install, and you won’t really get any additional power benefits.

Project: Upgrading a Cat-Back Exhaust

       The heart of the Corsa exhaust is the RSC mufflers, and the great-looking exhaust tips. The reflective sound cancellation system is designed to prevent exhaust drone by shaping the interior of the muffler to reflect and cancel sound that would otherwise build into a standing wave. One other reason to spend the money on a reputable, quality cat-back is the fit: A cheap unit may not have the proper clearances and can melt the bumper cover.

      This project installs the Corsa RSC (Reflective Sound Cancellation) cat-back exhaust system on the project 1996 328i. This product uses twin 2.25-inch OD T-304 stainless tubes and dual mufflers. Inside the mufflers, the exhaust gases pass straight through; the mufflers are designed to reduce noise without impeding gas flow. With the previously installed cold-air intake, this is an obvious next step in performance modification.

      Tip: If you’re considering installing a limited-slip differential or reinforcing the rear subframe mounts, now is a great time to do that, as you have to remove the exhaust from the car to do those projects.

      If you have access to a safe automotive lift, this project is easy and convenient. You can do the work using only jack stands, but it takes longer and is more difficult. Always follow the manufacturer’s specific instructions.

      Follow These Steps

       Disconnect the battery and raise the car. There’s no risk of electric shock, but this resets the DME so it recalibrates to the new exhaust. To ensure that the DME is completely drained and reset, disconnect both battery leads and remove the battery from the car. Then zip-tie the positive and negative battery leads together with the clamps touching for about 30 minutes to completely drain the DME capacitor while you are working.

       Unbolt the stock cat-back exhaust segment from the rear end of the catalytic converter. Remove the four bolts that connect the two pipes. These are 13-mm bolts and nuts, so you need two wrenches. One pipe connection is a slip-fit and the other uses a ring gasket, but be sure to catch and save that gasket as the pieces come apart! Next, unbolt the exhaust hangers on either side of the mufflers, while supporting the rear end of the exhaust. With the hangers loose, the exhaust should come loose and drop out easily.

      Tip: Spray some WD-40 lubricant on the rubber exhaust hangers and work them off gently because the rubber hangers are easy to break.

       To begin the installation, place the car in the air. You can see the old, stock cat-back on the bottom.

       Exhaust systems tend to rust far more than other areas because their heat cycles encourage the metal to soak up moisture from the air, and because of water splashed up from underneath the car. Plan on some work to lossen these nuts and have some penetrating oil and a heat source, such as a handheld propane torch, ready to go.

       Apply the oil and wait, then apply heat from the torch to the nut. Patience helps loosen a lot of rusty parts, but if you have to cut the system apart, an angle grinder is the easiest and least expensive method. Just plug in the angle grinder and turn it on. Then hold the grinding surface to the stuck nuts and grind them until the part comes free.

       With the exhaust bolts disconnected (or broken, or cut through) you can start to separate the cat-back section from the rest of the exhaust.

       Remove the exhaust hangers from the stock exhaust unit and place them on the aftermarket replacement. The stock hangers can be reused on the outboard sides of the mufflers if they are in good condition. New OEM replacements should be used if the old hangers are suspect or broken. The hangers are not symmetrical and the larger space should be oriented toward the exhaust tips.

       Exhaust hangers have metal frames supporting rubber mounts, to help let the exhaust move in relation to the other components, but to keep it within boundaries.

       Use the shop stand (or make one) to support the front end of the cat-back exhaust while you’re undoing the hangers at the rear of the car.

       Simply install the existing hangers back onto the Corsa cat-back exhaust. If the rubber is decayed or broken, replace the hanger.

       Position the new exhaust to the car and adjust the fitment of all parts. Make sure you put the ring gasket back into its space between the catalyst section and the cat-back section. Then, working front to back, tighten the bolts throughout the system. Make sure the exhaust is centered in its space at the bumper and that adequate clearance is provided all around. Run your hands along the top of the exhaust path and anywhere that the heat shielding is too close to let your fingers by, press it up and out of the way.

       One side of the exhaust slides into the new cat-back, while the other side simply mates with a ring seal. This is to allow for easy installation.

       Installing the ring seal into the exhaust is important to prevent stinky and annoying exhaust leaks. It’s a tricky fit-up process sometimes so take your time.

       Tighten the side with the ring seal first. The slide-in section of the other side holds itself in place while you work.

       Reconnect the battery and lower the car to the ground. You are ready to test-fire the car. Listen for rattles