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DIY Guide MPE & M235/40 Diffiser

10K views 5 replies 6 participants last post by  Matt88 
#1 ·
OK, hopefully this is of some use to some of you.

I had to DIY fit my MPE and performance diffuser due to MPE availability at time of delivery of my M240.
The job was exceptionaly easy!

Difficulty

3 out of 10
Took 1 hour

Difficulty score key:

1 = My granny could do it
5 = Expect some grased knuckles
10 = Warn the neighbors, there will be bad language and blood spilt.

Tools required:

Socket set (8mm, 14mm & 17mm sockets required)
Reciprocating Saw
Flathead Screwdrive
Ramps, jack and axle stands. (not essential as you will soon see)

Procedure:

1) Get the rear of the car up in the air, you do not need much room to be fair. I got away with reversing onto two unused mono block.


2) Remove the stock diffuser. There are 6 x 8mm nuts and two plastic pop rivets right at the end of the diffuser. You may have to use the flat head screwdriver to help you undo the rivets at the end.



3) Once the nuts and rivets are removed you can literally pull the stock diffuser towards you, it will pop out no problem.



4) Place this aside for now, as we now want to remove the backbox. (if you are replacing diffuser only skip to step 8] Look along the exhaust pipe , approximately 4-6 inches back from the backbox you will see a dimple.


5) BMW kindly placed this dimple here to show you where to cut the pipe. Take your tool of desired choice, i personally went with a reciprocating saw which cut through it effortlessly. (Yes that is a bit of condensation on the exhaust because I did start the car up like this ... hehe!)


6) Unclip the exhaust valve.

7) Rather than trying to pull the backbox off of the hangers in its current position, i opted to completely drop one of the hangers. This made life much easier to remove the rubber hanger bush. To drop a complete hanger all you need is a 14mm socket.


8 ) Completely remove the backbox, pull the rubber bush and hanger assembly off the backbox and place it on the new one.

9) Now with the exhaust off you have to remove the heat shield in order to add the additional supports. (you can do this with the backbox in place if you are upgrading diffuser only) . Remove 3 x 8mm nuts that hold the heat shield in place, pull the heat shield out towards you.


10) Add supporting brackets, tuck them under the clips to secure them in place.



11) Assemble the heat shield back to the car with the new supports in place.

12) Slide the MPE onto the mid pipe, push the exhaust into the existing hanger, some GT80, WD40 or any kind of lube will help here.

13) Bolt the other side (complete hanger assembly) back to the car

14) Do not tighten the exhaust clamp yet as it may to some fiddling to get it sitting correctly afterwards.

15) Adding the m-performance diffuser. Basically, just the reverse of the removal.

16) Line up the diffuser, ensure the bottom of the diffuser is below the heat shield.

17) line up the clips and push them in, This is very difficult ! I done both sides first.

1:cool2: Clipping in the centre takes some doing, i found the easiest way to do this is the pull the bottom of the diffuser towards you (quite far) then hit the area where the clips are very hard with the base of your hand. just pushing them in without pulling the diffuser towards me was not working at all.

19) Align the exhaust as best as you can with the tip in place, its useful to have a mate handy here. Once you are happy with the alignment get under the car and tighten the clamp with a 17mm socket.


If you have any questions or queries please do not hesitate to drop me a PM.

Thanks
Chris
 
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