Old Man's 1980-83 E21/320i, 2-1/4" exhaust system installed
My system has been in my 80 320iS for 4 months now
Doing great - sorry looks bad in places due to engine and tranny oil leaks, here are some installation tips.

The main Pieces - top picture
Top to bottom - left to right;
*Down pipe *Second pipe "S" pipe *Third pipe After Cat back to over the rear sub frame *To the left is the fourth pipe under the half shaft and up to the muffler *To the right of it is the tail pipe muffler back and out *Straight pipe next to the boxed muffler is the cat eliminator pipe, which goes in place of the cat.






In the bottom picture above;
*At left is the hanger for the stock position just behind the half shaft on drivers side.
*Down the middle are the three U-bolt muffler clamps
*At the right are the two stainless steel band clamps for the Cat and a new manifold flange gasket.



1) Jack car up and position it on approved jack stands, the taller the better.

2) To Start; remove old system; NOTE, I recommend using a good penetrating oil on all the nuts and bolts 12 hours prior to trying to take them off.
You will need to reuse the stock flange to manifold Nuts, the stock front hanger mount on the tranny and the stock 6" round muffler hanger.

3) Lay out all the parts so you can acquaint yourself with all the pieces and clamps.

4) You need to clean off all old gasket material from the exhaust manifold, after which put the new supplied gasket on the manifold and slide the flange of the down pipe up over the bolts and into place. Using the stock nuts, secure the down pipe to the exhaust manifold, this can be done using a 3/8"ratchet or the box end of a combination wrench. I did mine from the open over the fender.




5) Next locate the Second pipe, the "S" pipe and one u-bolt pipe clamp. Slide the clamp onto the end of the down pipe and then slide the enlarged end of the S pipe over the down pipe. Level the S pipe and using the stock hanger bolts and rubber bushings attach the welded hanger on the S pipe to the hanger plate mounted to the rear of the tranny. Make sure the S pipe is up into the middle of the car before tightening the pipe clamp, Note third picture below shows how it angles up into the drive shaft valley. When you are satisfied with the rear height of the S pipe tighten down the clamp and hanger so the S pipe does not move.







NOTE: I highly recommend you do not install your cat for the first 200 miles of driving with the new system. The bender used a lot of heavy machining oil on the mandrel when the tube were bent, the exhaust is going to smoke allot for the first hour or so and continue to smoke more for a week, the oil also smells when it burns off, SORRY. I'm not sure the smoke will be good for the cat insides.

The said; Take one of the band clamps and slide it over the S pipe end then slide on the cat eliminator pipe or the cat and slide the clamp 3/4's of the way over the cat end and tighten the clamp up awhile assuring the cat flat with the bottom of the car.
Sorry on picture of the cat eliminator pipe on the car.

NOTE: It is illegal to operate your car on the street without a cat., the cat eliminator pipe is intended for off road use only.







Next is the most critical pipe to install, due to the bends at the rear. If the pipe is twisted/rotated too much one way or the other then the fourth/next pipe that goes under the half shaft will not line up correctly for proper muffle installation.

So slide the second band clamp onto the cat end and slide the bent end of the third pipe up in between the drive shaft and the drives gas tank. Go over the cross over tube between the tanks, over the rear sub frame and back, then left the front of the pipe to the rear of the cat and slide it into the cat outlet. Slide the band clamp back so it is off the end of the cat about 1/8" and snug it down, you want to be able to rotate the cat back pipe if needed. Make sure the clamp on the front of the cat and S pipe are tight so the cat will not turn if you twist the cat back pipe.










At the back the pipe should be at about a 45 deg. angle pointing towards ground and drives rear tire






Next slide the U-bolt Hanger over the end of the third pipe and hook the end up in the stock rubber hanger.

The fourth pipe slides over and onto the end of the third pipe and is clamped to the third with the hanger U-bolt clamp. snug up the u-bolt, BUT leave it loose so the two pipes can be rotated as needed.





Muffler installs with the welded mount loop on one end towards the front of the car.



So now:
Loosely fit stock muffler hanger onto muffler and hold it up under the car in position and mark where clamp should go. Take muffler down and slide clamp to where it should go. Next slide a u-bolt clamp onto pipe and then slide muffler over and onto the fourth pipe the length of the inlet piece on muffler. Replace the rubber hangers on the stock muffler mount and check the alignment of the muffler with the cut out in the rear of body for the tail pipe. The rotation of the muffler itself is also critical.

Now comes the twisting and turning of the third and fourth pipes along with the muffler to make sure the system:
1) Does not hit the car or any of it's parts.
2) And that the muffler outlet is pointing towards the tail pipe cut out, it actually points to the outside of the cutout for the tail pipe bends over to go out the cutout.

The closest point of the system to the car is where it passes between the drive shaft and drivers side gas tank heat shield, as seen in the above pictures.
When you think you have it close to being, right hit the muffler with the plum of your hand to see if it moves enough to hit. This took me the longest time during the install - but it can be done and my system has been in for two track days and lots of street and freeway driving. It does not hit anywhere.







Once you have the alignments to your satisfaction, tighten up the clamps, the one on the rear of the cat, the U-bolt hanger clamp over the half shaft, and the clamp on the muffler to fourth pipe. Also tighten up the stock muffler hanger clamp.

Last to do is install the tail pipe:

So slide the last U bolt clamp onto the muffler outlet pipe and slide the tail pipe into the muffler outlet and twist it into place. You can slide the tail pipe into the muffler up to the bend if you like to get the tip of the tail pipe where you want it.

I made the tail pipes long for those of us who do not want black exhaust soot on the back of their cars, but you can cut the end to your liking.



You can also adjust how loud your system is, by how long the tail pipe is.
I drove for almost three months without a tail pipe while they were being made and it was too load for me.

But it sounded good and fast..