Finally got around to installing this sexy little diffuser this weekend and feel great because this is literally the first time I've ever done this kind of stuff to a car and I'm very happy with the results.

Just to be clear - none of this is REQUIRED to install this diffuser. I simply wanted a more flush fitment. You could easily install it in 5 minutes by throwing some 3m tape on and sticking it right onto the bumper like you are supposed to and everyone else has done and is happy with (see https://mbworld.org/forums/w211-amg/...0-shipped.html). But I chose to replace the bumper with the diffuser instead of mounting it onto it.

This is my second DIY and they're kind of long but I like to be very clear and detailed about everything so that even the biggest noob (like me) can understand how to do it. And I include a short version anyways for the more experienced people so bite me! Just kidding please don't bite me..

Ok...

Lets get it on!
Tools needed:
-Some type of power tool to [cleanly] cut the stock bumper. I bought an oscillating multifunction tool from harbor freight for $40 and it came with the cutter attachment
-Dremel with sandpaper attachment
-Sockets
-Zip ties
-Double sided tape (not REQUIRED)
-Small self drilling/tapping screws
-Safety glases
-Painters mask or something to cover your mouth/nose from breathing in dust
-A friend to help with holding the diffuser in place and helping with fitment and such


Short version
Remove thin plastic cover from bumper. Carefully cut out a chunk of the bumper where the diffuser will go. Dremel the edge to finalize it and make it a clean cut and a clean fit for the diffuser to go on. Drill 3 holes into the crash bar and then mount the diffuser with screws. You can stop here, or drill a hole into the left and right side of the diffuser and use zip ties to hold it up for a better fitment on the sides. Done!


Extended cut
First step is to remove the thin plastic piece from the middle of the bumper. It's stuck on with double sided tape so just use a heat gun while you pull it off.

Once that is off you will see an indented line that goes along the bumper, the line that the diffuser would sit in if you were to simply tape it on. There are 2 edges at the top of this line and you are going to cut about 1mm below the very top edge, leaving 1mm to dremel/sand away and perfect the cut and/or correct any mistakes. What I did was carefully placed some blue painters tape about half a millimeter above the edge to use as a guide while I was cutting because the dust will get in the way while you're cutting and it's hard to see the edge and you might cut too far upward. For now just cut out the middle piece along the indentation, afterward you'll have to hold the diffuser up to the bumper and use a marker or something to mark the right/left sides of the bumper (and then place tape as a guide) where the ends of the diffuser go because there aren't any simple lines to follow there. Just make sure you cut way below where needed to be safe and you can go back later with the dremel and shave the rest off to make it perfect.


Take your time cutting and make sure your cut is clean! It is obviously the most crucial part to making this look nice and you could easily make an ugly mistake. After you have cut out the middle piece and marked the left/right sides and cut those out too you will begin perfecting the cut line with a dremel. This is very time consuming yet relaxing in my opinion, and you want it to look nice don't you? It took me about 2-3 hours laying under the car jamming to music and dremeling away. Just keep shaving small areas away with the sandpaper dremel attachment and then holding up the diffuser over and over until it finally fits right where you want it. You will spend 90% of your time dremeling the curved parts nicely so that it will sit up into the bumper right. ALSO - you'll want to use the dremel to shave an angle or 'sharp edge' into the cut so that the outside painted part of the bumper will sit flush against the diffuser and not have a gap where you can tell the bumper is cut. You'll see what I mean when you're doing it.


Once the diffuser is able to sit right where you want it you're ready to drill 3 small holes into the little lip that comes off the bottom of the steel crash bar beneath the plastic bumper. The diffuser will be mounted with some small screws. Make sure you wear some glasses so you don't get any metal shavings in your eyes!


I chose to re-use the 2 stock bumper brackets by cutting them out of the bumper piece that was cut off and double sided taping them to the back of the diffuser. I had a friend hold the diffuser in place on the car while I layed under it and held the bracket piece in place and marked on the diffuser where it needs to go, then taped it to it. I really don't think this is necessary but I was on a roll and thought I was clever in doing it so yeah lol. Plus it's another thing holding the diffuser on and doesn't take that long to do.


Now you're ready to mount this sucker up! This is where you will most likely need a friend to help. Have them hold the diffuser right where you want it while you screw it to the crash bar. I actually had to re-drill 2 holes in the crash bar again and re-mount it because it was sitting too low the first time. Also, since the diffuser is curved a bit and the crash bar isn't it may sit a little weird compared to when you simply held it in place. But don't get discouraged, just have patience and work on getting it to bolt up nicely. It helps if you put the middle screw in last since that is the one that's going to pull the curve of the diffuser in. My friend had to really press the left/right sides of the diffuser up hard while I put the screws in to get the proper fitment after letting it go.


Now you COULD stop here, but I wasn't content with how the sides of the diffuser were sitting (hanging too low). At first I tried to make a little bracket and use double sided tape to hold it up but the tape wasn't strong enough. So after some brainstorming I decided to drill a small hole into each side of the diffuser and zip tie it up to the exhaust hangers, I was going to drill holes into the crash bar again and zip tie it there but it looked like a real pain and I figured it's fine this way. And yes I know my bumper is cracked like an inch in the pic, not sure if I did that while messing around doing all of this or if it was already there. argggg! Be careful.


..and you're done baby! Hopefully I pissed off some people who paid $400-$700 for a more flush fitting diffuser (just kidding!). Total invested in this project is about $260 ($200 diffuser, $40 cutting tool, $20 misc stuff). Please snap some pics and post 'em here to show off your skills!

Here's some pics of the final fitment I've got now :






Attaching the pictures below to the thread in case the ones above disappear in the future....

 

rest of the pics..

 

rest of the pics...

 

Clean those tips

 

I know I know.

I brushed the hell out of them with a plastic brush and scrubbed them with metal polish and the whole nine and still can't get them shiny all the way around. Any tips?

 

Nice DIY! I'll make sure to check it out again when it's time to do mine.

 

WOW, Great write up, thank you and finished product looks great.

 

Detailers domain sells a polishing soap... its worth its wait in gold.

P21S Polishing soap

 

Nice write up... looks good !!

 

Hey how did you do the chrome trim around the lower mesh grille on the bumper? It looks nice.

 

Looks awesome!!! now get some daytime picture!!

 

I haven't had the ability to try Polishing Soap yet, which I really want to, but #0000 steel wool with some metal polish will give you the bite you need to really clean the tips

 

Not sure what trim you're talking about. The chrome piece below the license plate? Whoever I bought the car from put that on there.
Edit: ohhhhh you must be talking about my sig. Yeah.. the person I bought it from did all of that. It just some plastic/rubbery flexible chrome trim stuff you can probably buy at autozone or something. I thought the car came like that but apparently not lol. It does look good though I like it. It's also around the headlights and foglights but you can't really tell in the small pic, here I'll attach some bigger ones..


Here's a couple daytime pics for you guys..

 

I used Mr Clean magic eraser. Worked like a charm for me and it was easy. Can purchase at your local supermarket.

 

Wow that looks great! The diffuser when applied over the bumper has kind of a cheap look to it, like the car is wearing a diaper but you got it right on target. Good work!

 

Thanks for the close ups. I find it very tastefully done rather than what the chrome stuff is typically used for when found on run of the mill cars. I'm thinking about doing the same to mine.

 

Sorry for open this old thread up but found it suitable for my quistion.
Is the defuser flexible or total stiff?
Asking because the one I got is stiff but seems tj3 bumber is shape bending now just tried on top damn a huge cap can this really work or is it better removing the bumber when installing it?

I'm doing this differently was matte black had both defuser and lip painted black gloss think will look awesome on the diamond Silber with black windows black grill gloss..


Unfortunately got hit by a truck Friday on way to pick it up from painter sucks front bumper lower part chipped right door dended so first paint and repair job ahead hit some plastic road signs damn lucky wasn't worker but still sucks want to kill my selfe my baby got beaten anyway no person injured just stupid driving