Thanks to all for providing potential upgrade paths for older cars without HEPA.
I have an "early" 2021 Model Y, built in Dec 2020. This is one of the first cars rolling off Fremont for 2021, and had the updated interior with the laminated glass, glovebox USB, and metal scroll wheels.
View attachment 815894
View attachment 815896
It doesn't look like I can perform this upgrade easily:
1. Only 2 of the 4 holes needed for the HEPA duct are there. The 2 missing holes are for the alignment pins on the HEPA duct.
2. On the available 2 holes, they are not threaded. I measured these holes with a caliper at exactly 7mm wide.
3. The holes are only about 0.5" inch deep, and I can see a metal plate underneath. It will be difficult to drill through that lower plate.
4. Even if I drill a hole through the bottom plate, the screws (inserted from the top) will need to be secured from the bottom wheelwell area with a nut. I don't want anything that can loosen and fall off down there.
5. Rivet nuts inserted from the top are an option in lieu of #5, but it would need to be a super tight fit to make sure it doesn't come loose and fall out of the frame.
Overall, I don't feel comfortable drilling holes down into the body without knowing what's underneath.
Unfortunately, I will pass on this upgrade. Instead I'll resort to continue using only recirculate for air filtration, and A/C on manual to control condensation/smells.
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Another option without drilling may be to Dremel out the alignment pins on the plastic duct box, and just doubleside tape the duct to the metal chassis. I think the pressure from a closed frunk may hold it in adequately?