Although I have yet to commit to a particular shop, I recently commited to starting this project. This prompted a whole chain of events: measure, disassemble, test fit, modify, order parts, and eventually, drop off for paint. This process will be documented over many posts moving forward. For the purposes of this thread, this will be considered Phase 2: Exterior Body & Paint.
First, I took measurements of all the panel gaps for the trunk, diffuser, front bumper, rear bumper, etc. This way I had a good reference moving forward on what the gaps were. The goal was to either equal or improve the existing gaps for the new components.
I then took all the CSL components down from storage. Penny (my golden retriever) knew something was up. She doesn’t normally come out to the garage but she wanted to check out what was going on. She was not impressed.
I started with what I thought would be the easiest of the new components, the diffuser. The factory diffuser (and 5 pounds of rocks/dirt) came off easily. The Vorsteiner diffuser got its first test fit. The fitment was 80% there with no modifications at all. The panel gaps were actually even better than the factory piece in most places.
That said, the top of the diffuser refused to sit flush with the bumper. If you look closely you can see it’s sitting about 1mm-2mm proud of the bumper.
There were two minor issues. One was that Vorsteiner made the center alignment tab too wide. It was just wide enough that it wouldn’t push fully into the hole in the factory bumper. This fix was really simple, open up the alignment hole in the bumper, and take a tiny bit of material off the diffuser.
The second issue was that the lip on the top/backside of the diffuser that hooks into the bumper varied in width. It was anywhere between 0.25mm and 2mm too wide compared to the factory piece. This fix was more involved. It required me to take measurements off of the factory piece, score the Vorsteiner diffuser with a micrometer, then use an orbital sander to shave down the lip, matching the dimensions of the factory diffuser.
First the top section.
Afterward it sat perfectly flush and the gap was far better than factory.
Then I moved onto the sides utilizing the same method. Take a little off then test fit. Repeat as necessary.
After those tweaks, fitment was perfect. Here you can see how I checked the alignment of the two pieces. Long story short, if you’re looking for CSL diffuser with zero fitment required, send Gt4 a message.
Next up was removal of the rear bumper.
While the bumper was off, I installed some “Eurostyle” exhaust tips. They are slightly larger diameter and have a more substantial dual wall design that I thought would pair really nicely with the new diffuser. First the factory rivets were drilled out. Then the tips were easily removed.
Here is a side by side comparison/mockup and a full mock up afterwards.
I couldn’t resist cleaning the area before installing the exhaust tips. After a deep cleaning session I measured the tips for perfect alignment, then secured with metal rivets.
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