BMW E85/86 Z4 M Coupe Exhaust Removal and
BMS Performance Exhaust Installation
When I first brought my M Coupe home, I loved everything about the car but the silence. To me exhaust sound has always been one more way for me to connect to the car. Some other manufacturers had some exhausts on the market but I elected to try the BMS exhaust system (http://www.bmsracecars.com).
Pics of the exhaust system when it arrived, consisting of a new X-Pipe (sans resonator) and new mufflers:
NOTE: The following is provided for information only and any use of this information by you is at your own risk.
The secondary cats located in front of the X-Pipe do not have to be removed, but since it was easier to get to the two bolts holding it to the exhaust manifold than the three bolts for the X-Pipe to secondary cat pipe junction, I elected to remove the entire center section as a unit and disassemble it when off of the car. In order to access the components under the car I used a ramp and jack stand combination. To remove the four bolts I used a size E12 external Torx socket (also called a reverse Torx) and a 14 mm metric wrench:
Disconnecting both rear cans makes it a little easier when not using a lift to remove the center section by itself, this is accomplished using a 13mm box end wrench and a 13mm socket wrench. There is a seal located between the two flanges and two nuts/bolts on each side:
To access the hanger bolts to remove the rear mufflers the plastic plate underneath the rear section will have to be removed, 8-8mm bolts and 2-12 mm plastic nuts:
One of the rear braces will need to be removed to allow the center section to be removed, left or right side does not matter. The brace is held on to the car with a 14mm bolt at either end and a 10mm hex head screw in the middle brace support:
The front and rear hanger bolts to the mufflers can be removed with a 13mm wrench; the nuts on the OE muffler hanger mounts are welded and will not spin. There are two hangers per muffler:
The next step was to remove the hex head screws holding the aluminum cover plate to the center section support brace to access the bolts for the brace. This is done using an 8mm socket wrench, 5 screws in front/ 1 screw in the middle/ 2 screws in the back:
Next the bolts for the support brace can be removed, 4-14 mm bolts and 2-12mm bolts. You may want to use a jack to support the center exhaust assembly because it will drop when these bolts are removed from the support. The exhaust is removed by pulling assembly to the rear to disconnect the front pipes and then moved forward to clear the remaining rear brace:
The secondary cat section can be separated from the X-Pipe by removing the 6 nuts and bolts (both 13mm). The gaskets should be carefully removed for re-use. The X-Pipe can be removed from the center support by removing the two bolts from the support:
Installation is reverse of above steps. The OE hardware can be re-used, but the two hanger bolts must be swapped between the front and rear muffler mounts to allow for fitment of the BMS mufflers. Nuts will also need to be sourced for these four bolts, future BMS exhaust shipments should include all necessary hardware. The alignment of the tips for symmetry and centering may require some fine tuning of the muffler to center pipe clamp bolts:
Some installed pics:
TIS Torque Specs: TIS instructions below with torque specs-