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      12-28-2021, 05:40 PM   #254
argento's Avatar

Drives: 2013 X5M
Join Date: Mar 2012
Location: Houston

iTrader: (0)

Continued from Page 11, Posts #232 (part received), #234 (vendor info), #238 (test fit). Corrections from previous posts: The diffuser DOES follow the OEM diffuser outline once installed and the outer edges pushed into position. I was able to install the diffuser w/o removing the rear bumper and I now recommend this as it keeps the bumper static while you apply pressure to the diffuser for install. I did not use 3M double sided tape and I don't believe it would help b/c the tension created by the diffuser is pretty high.

FINALLY got this installed today and I do recommend this product for the price. This is my second diffuser install (E46M3) and based on my expectations I'd give this product an "A-". To get a higher score this item would need to include hardware that is usable, provide clean thru holes that are actually drilled all the way through, and be installed with little effort. Despite this I was actually able to install the diffuser to look satisfactory and I could probably spend more time and effort to get it slightly better.

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-8mm Socket to remove OEM Screws from lower bumper
-Phillips Head Screwdriver
-5/32" Drill Bit for pilot holes
-13/16" Drill Bit if needed to drill out diffuser thru-holes
-Scratch Awl to mark pilot holes on bumper

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-Throw away the random hardware that came with the diffuser and purchase as shown in pic:
-McMaster Carr, Qty.1, 90399A249, Rounded Head Screws with Washer for Sheet Metal, Black-Phosphate Steel, Number 10 Size,1-1/4" Long, Packs of 50 (or equivalent).
-McMaster Carr, Qty.1, 94808A153, Black-Phosphate Steel No-Slip Clip-On Nut, 10-24 Thread, for 0.13" Maximum Thickness, 0.31" Hole Center to Edge, Packs of 25 (or OEM C-Clip Nuts or equivalent for sheetmetal screws)
-#10 Rubber Washer, Min. Qty.4. (happen to have these already in my toolbox)

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CAUTION! USE PPE Wear a mask and eye protection PPE as carbon fiber dust can get into your eyes and lungs. Use gloves to avoid carbon fiber splinters from the diffuser. ALSO - The diffuser manufacturer recommends this be installed by a professional. This installation DIY is for REFERENCE ONLY
1. Remove two screws on center bottom of bumper cover using 8mm socket. Leave OEM C-Clip Nuts in place as they will be reused
2. Mount diffuser using center two bolt locations to OEM C-Clip Nuts using Screws and Rubber Washers. First mount loosely to make sure diffuser is centered, then tighten. If these fasteners are loose, then you will not create an accurate mark for the pilot hole on the outside fasteners. NOTE: The tightness of these fasteners can have influence on the final location of the diffuser against the bumper cover. By tightening here first, hopefully this will make your pilot holes more accurate and make final installation easier.
3. Starting on one side, use moderate force to align the diffuser to the OEM diffuser outline and hold. Then use the scratch awl to mark the pilot hole location on the bumper cover so it is aligned to the thru hole on the diffuser. NOTE: This is a critical step, so try to be as accurate as possible. If the mark/hole is too far toward the front of the vehicle, it will pull the diffuser top edge away from the bumper cover on final install. If the mark/hole is too far toward the rear of the vehicle the diffuser could sit loose. I recommend marking the hole as far forward as allowed by the diffuser through hole. If needed, b/c the diffuser does not sit correctly on final install, you can file the hole toward the rear of the vehicle creating a slot as needed. If you mark and cut the hole furthest aft, you can no longer move the hole toward the front of the vehicle, at least not without some repair work to patch the hole and drill again. IF you need to repair the hole, then I recommend taping the hole, punching the hole to clear the tape, use JB Weld plastic to fill the hole, then remove the tape and let dry.
4. Drill the pilot hole on the mark using a 5/32" drill bit. This allows the threads of the #10 sheetmetal screw to bite into the plastic bumper cover for added rigidity, in addition to the c-clip nut.

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5. Repeat pilot hole for opposite side.
6. Next, ideally, you just reassemble the diffuser using the screws, washers, and c-clips. I used the mcmaster c-clips as basic nuts on the pilot hole fastening. Once the sheetmetal screw protrudes on the opposite side of the bumper cover, manually install the c-clip nut, rotating until it is tight, then continue with tightening of the sheetmetal screw.
7. In my case, at this point, I had trouble getting the diffuser upper corners to sit up against the bumper cover. I did not use the strategy above to mark the pilot holes, that was developed after the fact as I struggled to make adjustments. I loosened and tightened the four fasteners various times to get an understanding of how the diffuser is affected by the tightness of the four fasteners. After many iterations the diffuser sits as shown in the pix above. In my case, loosening the pilot hole fastening allowed the corners to sit closer to the bumper cover.
8. Good Luck! Next to install the Arka muffler and improve those exhaust tips...

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3Jan2022 - Diffuser Update - LESSON LEARNED....

I've driven 22 miles since installation of the diffuser and found bubbles on top near the exhaust tips. Contacted the vendor and their guess was high heat to which all resins are susceptible. Then I remembered, in those 22 miles I had about two 30m stints in idle while I fielded work calls. That coupled with the tips sitting inset and exhaust gasses folding up and over the diffuser edge...HIGH HEAT EXPOSURE! Disappointing, but I only notice up close and like everything else it's easily replaceable if needed.

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Last edited by argento; 01-04-2022 at 09:01 AM.. Reason: Lesson Learned
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