Fitting the OEM Carbon rear diffuser ('07 coupe)

B

Breaker

New member
Started this thread as I didn't want to hijack someone else's. I've done a search and can't find anything.

I ordered the carbon rear diffuser at the weekend and it is now at the dealers. I'll pick it up later this week.

Anyone actually finished fitting one of these yet?

I was wondering if it is possible to fit it without removing the rear bumper cover?
I think you could do the cut out on the car but I'm not sure you would get to the bolts holding the diffuser in place.

Are there any instructions on the net for removing the rear bumper cover? I've had a quick look but can't find anything?

Thanks in advance. :)
 
Hi - thanks to the wonder of mobile internet while sat in the shop getting my geo set up I can give some thoughts:

Firstly there is one member who has fitted on as I hijacked his photo for my research thread.

When you collect it ask for the instructions. They'll print off from their system as they are not in the box.

Having had mine on the bench for a week I see no way it can be fitted in situ:
1) there's a lot of plastic cutting and a possibility of cutting into other goodies from hanging down PDC cables. etc.
2) the top edge is held on by 9pan head bolts, 4 of which are so awkward that they come with wires welded to the top that are used to hold them in position while nuts are fixed. They are then tin snipped off.
3) OEM instructions specify removing it.

Removing the bumper will be in the TIS but to me it looks like remove the trim along the boot lip, undo some torx there. Unclip the wheel arch mounting pins and then 4 or 5 bolts underneath. Should just then unclip from the sides behind the wheel from the rear quarter, similar to the front.
I can find the section and email you tonight if needed.
 
Thanks. I think I realise it can't be done on the car to be honest!

That Email would be handy if you have time. :thumbsup:
 
em, what OEM carbon rear diffuser is that? any pics? that's the kind of expensive mod i like! More details on cost etc would also be appreciated.
 
Check this thread: http://www.z4-forum.com/forum/viewtopic.php?f=2&t=9267

By the way, BMW don't do one for the M! :wink:
 
BMW install instructions quote 2 hours for the post 2006 carbon diffuser. Times quoted are assuming no paintwork (which I can't see whay it would unless the existing is damaged by them... and 'depends upon equipment fitted'. Guess that means £240 basic at the dealer to do it plus VAT.
 
Yeah right....I agree, but that's BMW for you.

Here's a scan of bumper removal on a roadster FYI. As suggested earlier it's a real quick job:

I think the coupe has another row of clips under the bootlid trim, but you can check that

bumperremoval.jpg
 
Breaker said:
Thanks for that. :thumbsup:

Looking on real OEM there are some screws under the top trim.
Click to expand...

Yep - as per my post. clips, screws, whatever. Located on the roadster under a black trim cover. For some reason not mentioned on the TIS page
 
I'm picking the diffuser up Friday afternoon (it's at the dealers now) so I just need to pluck up the courage to take off the bumper and cut it out!!

Unfortunately it probably won't be for a few weeks yet as I have a very busy calender for the next 2 months!! :(

I work for a commercial vehicle body building company (IT and office bound now) so they have loads of tools I can borrow. The one tool is a small circular saw designed for cutting out glass fibre. It has a very fine toothed blade. Beauty of that is there is no sawing action so the paint shouldn't chip. The only problem can be heat build up though.

I may even get the shop floor guys to cut it out for me yet! :wink:
 
I too am stopped in my tracks due to work and other car issues to sort out....

Nice to have a bodyshop on hand. My plan will be to run a fine dremmel line along the final cut line to isolate any paint splinter. In fact aside the curves over the exhaust there is a lot of remaining material to work with so shoudl not be too bad.

I'd fit mine soon except the bigger job of battery moving needs doing and I don't want to drive around for weeks with dual outlet and single exhaust - too Corsa/ Saxo :thumbsdown:
 
I'll try and get some pics when I install it including the bumber removal (if I have time!!).

If it works, I'll post them, if it doesn't I'll be homeless so wont have access to a computer (the misses has threatened to kick me out if I mess up the Z4!!!........and it's my car!!!). :P
 
cj10jeeper said:
Breaker said:
Thanks for that. :thumbsup:

Looking on real OEM there are some screws under the top trim.
Click to expand...

Yep - as per my post. clips, screws, whatever. Located on the roadster under a black trim cover. For some reason not mentioned on the TIS page
Click to expand...

Actually, looking at the RealOEM picture I think the top fixing (item 5) is a push fit clip, not screwed in. The screws on the picture are to secure the holder.

MTQ2MTg0X3A.png
 
Could be - I've not looked.

That said 9&10 look suspiciously like hex headed self tappers and their fixings. I'll know when I get around to pullin git to bits. Either way it's a 30 second job
 
OK. A few pics that will hopefully give people an idea of what's involved in fitting the diffuser! Pictures don't do it justice to be honest! 8)


First the bumper cover has to come off. 3 plastic rivets in each wheel arch. Just pull the mandrills out of the centre (I used a thin flat blade screw driver to start them off). I didn't jack the car or take the wheels off to do this. Undo all bolts under the car. Then pull the top edges of the sides out as they are just held in by a support bracket. Then just pull the cover backwards releasing where the top of the bumper is trapped by another fixing bracket under the boot (trunk) lid. Easier to do if you have help. Pull back slightly once released as you will have to disconnect the number plate lamps wiring (pull connectors).

Pics of the cover removed:

002.jpg


003.jpg


006.jpg



Pics showing the support brackets for the bumper cover:

005.jpg


004.jpg



Next fix the supplied cutting and drilling template to the edge of the straight style line on the cover. The template is made of paper with an adhesive back. The template is positioned with the centre hole in line with the centre of the numberplate bolts. Take time to get this right as the "wings" on the diffuser follow the numberplate recesses slanting sides, and if not square, will look "odd".

007.jpg



Now the "no turning back, take a deep breath" bit!!! :o Drill the 5.5mm holes as per template BEFORE cutting the bumper out. The cover will be more solid!
Cut out the bumper!! Don't bother trying to cut around the template exactly to the curved tabs. Just cut it straight. I used a hand jigsaw I had with a fine blade. Cut easily. :thumbsup: NOTE: I did masking tape up the cover above the template just in case the jigsaw marked it. I used a drill to drill the corner radius's on the template before cutting.

008.jpg


009.jpg



Next loosely fit the diffuser to the cover with the centre bolt to check fit and adjust/cut more out if needed. I was amazed at how the diffuser fitted straight off. Even all the holes lined up without having to open out any holes!! Even the bumper sat centre!!
If happy, bolt the diffuser on using the bolts provided as per the instructions sequence. The 4 end bolts can be a bit tricky to get in!

NOTE: Use Loctite on the bolts as they come with plain nuts and washers only. BMW have done this because using lock-nuts on the bolts will chew the carbon when tightened as they are "captive" bolts in the carbon (squared locator under the bolt dome) and using spring washers on carbon can eventually cause cracking!

No photos of it fitted as I forgot to take them!! In too much rush to see it on the car!! :P

Fit the cover back on in reverse of taking off. making sure any panels under the battery box and the heat shield are sat inside the bumper cover!

Stand back and admire!! 8)

DSC_0013.jpg


DSC_0020.jpg


DSC_0015.jpg


DSC_0017.jpg


DSC_0016.jpg


013.jpg


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diffusertaister.jpg



:)
 
I sprayed up the metal bumper once the cover was off with some Hamerite black "smooth" spray because it was going slightly rusty on the welds!! :|
 
Nice job Breaker and glad you took a lot of photos. It looks superb, but then I'm a little biased... :)

BTW - can you imagine getting that cutting template in the right place if you didn't have the crease line to follow??
 
Nice job Breaker. Looks Great! :thumbsup: Could you do me a favor and take a pic from about 15 feet away? Trying to get a better idea of overall balance. So how long did the whole project take? Any issues putting the bumper back on?
 
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