Just to update my experience, the local Tesla Shop had the new twin-fan motor in stock, plus the modified anti-roll bar, as well as the "panel blower surround R2.0" which was the exact one for my 2.0 Roadster. There are different 'panel surrounds' for each of the Roadster models. So I immediately flat-bedded my Roadster to the Shop for a complete cleaning and the full blower upgrade. I was shown the 'panel surround' at the shop, but unfortunately did not think to take a photo. Having now inspected the surround with strong light it seems to be a very effective first step toward solving the dust-in-PEM problem. It is sealed to the pan with foam strips, but the 4 bottom corners are purposely opened to allow water, etc to drain out by gravity. The size of these openings is approx 3/8in. Also there are 2 gaps where the roll bar enters- less than 1/8in clearance around the bar perhaps. All around the top edge there is a varying gap amongst the castellations. Presumably this is where the bulk of the cooling air enters the box. Knife-edge filtering as it were.
Now, the box could easily be sealed up with expanding foam, to block all the openings just described. Then a 4in dia hole drilled in the trunk floor. Then air filters in some sort of housing could be fabricated. Filter elements are readily available for Olds Oddessy, etc 'cabin air filter'. You get a pair of filters for $16-US. STP-CAF1704. These filters are made for heater blowers, so are more appropriate for this application than are piston driven intake filters which may create more back-pressure. Having brought the air intake up and into the trunk, now we have to let outside air into the trunk. In my Roadster, however, the trunk is already quite dust-free, so nickel-sized holes could be drilled into either side adjacent to the latches, and routed into the filter housing.
But rather than continue with all this, I think I'll just stay off dirt roads whenever possible and see how much of a dust problem exists in 12 months time when the PEM is removed and cleaned out. Possibly there will not be much of a problem if the new fan surround does its job well. Even though the drought continues hereabouts, showers and sprinkles are happening daily, which drives the dust back into the surface. Tesla's solution might prove effective.
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