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While not required, since it is blowing at the driver’s face it would be nice if it did does not suck through fine particulate matter from the road. Intakes should also contain geometrical features to protect against water ingress.
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The intake/exhaust and ducting should aim to maintain a cross sectional area greater than a 4in diameter circle. Battery fans are This standard is currently based on nothing other than it feels off to have ducting less than half the area of the fans, which are a circle approximately 6in in diameter.
Filtration
We should try to maintain the same standard as for the driver, although there might be some room to relax it a little when it comes to fine particulate matter.