One of the quickest and simplest modifications you can do to your 928 is install a rear muffler by-pass. I bought my RMB, used from a fellow Sharkster here in Las Vegas.
My car is an 87s4 and from then engine back has.......two headers..that lead to 2 seperate CATS....that lead to 2 seperate mufflers...whos pipes then JOIN at a SINGLE MUFFLER in the rear. The single muffler in the rear is the one that I am bypassing. There are claims i believe of anywhere from 5-10 HP gains with the RMB. My first impression was that the engine seemed to REV more freely, in other words, the RPMS climbed quicker. The biggest thrill i got out of the RMB was the sound. This alone makes it worth installing. The car sounds pretty good in "stock" form but with the RMB it now sounds like it REEEEEAAAAALLY means business. At idle or plodding around town at 30-40 you can here the faint, deep,rumbling sound of WHHHHUG WHHHHHUG WHHHHUG WHHHHUG from the rear end. When you step on it.....well...you be the judge!! Its a pleasant sound, that at highway speeds i didnt find the least intrusive, besides, usually having a radio on and the windows down you cant hear much anyway! I actually find my self driving with the radio on LESS these days : )
Below are pictures of the installation that from the time i backed the car on the ramps to driving it off took only 53 minutes (and that was with taking these pictures).
Things you will need
1) 13mm socket and a wrench. You will need both as the bolts are usually rusted and the opposing side will spin if not held.
2) WD-40 or the like. Spray this on the bolts to be removed to help free them up. Mine were pretty bad. If you know you are going to do the job perhaps you can "presoak" them.
3) Saftey glasses, you will be on your back under the car and there is alot of CRUD that will drop off as you do your work.
4) RAMPS or a way to raise the car
5)FLOOR JACK...optional really. I did this job by myself and hearing that the REAR MUFFLER is quite heavy (it is!!)once its free i didnt want to risk having it fall on to....you know who...underneath! I simply supported the muffler with the jack thus freeing up all my hands to hold wrenches and manipulate the part. When it was all lose, a simple twist of a valve lowered the jack and the muffler to a point where i could grab it..
Here is the part....the pieces on either side are where the RMB hangs from the original rubber supports
Looking underneath at 13mm bolt #1
13mm bolt #2....i undid these first and then slid the clamps back. You will find that the muffler will still hang there as the flanges to the pipe/muffler interconnect somewhat. Like i said, i still had the jack ready underneath.
The next thing i did was remove the bolts that attatched the muffler to the rear RUBBER mounting supports, there are 2 of them on either side. TIP..YOU DONT HAVE TO REMOVE THE RUBBER!! just undo the bolt that joins the 2 brackets together. This picture shows the bolt allready removed. The silver part on the right is the underside of the rear bumper and the dark BOX in the lower left is the battery compartment for reference
This is the other 13mm bolt on the rubber hanger. This one is a bit of a pain to get at i found. As you can see the jack in the lower left lending a third hand. Besides, how are you to sip a beer when your hands are all tied up : ) Now with all the bolts removed, i just manipulated the muffler and it dropped and rested on the jack.
This is what it looks like all removed. To install the RMB just reverse the process. I started by mounting the brackets to the rubber hang points....the RMB, being light was easier to work with and i just let it hang there as i installed the clamps on the pipes.
ALL DONE!! just take the time to line up the RMB so it doesnt rest on the rear bumper area cut out for the muffler. You will find that the part is a perfect replacement!!
Roll down the windows, turn off the radio, turn off the blower , tell the "S.O." to be quite...... listen............and....turn the key! : )
Hope this helps a few of you with your desicion or installation..............I love it!