Quote:
Originally Posted by Raptor05121
and polishing it would make it smoother, so less parasitic drag on the sidewalls.
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That is the theory, but I've seen parties with advanced knowledge report that a shiny surface does little if anything to promote air flow.
Basically, there is a 'boundry layer' - a thin area of turbulent air near the surface, and it matters not whether the surface is polished smooth or not.
Bottom line is it may not be worth the trouble to polish.
If you want to flow more air, make the hole bigger. But remember that in many cases automotive, air velocity is important, too. So there can be a downside to going overly large.