[quote author=rubyred3 link=topic=42848.msg631466#msg631466 date=1143213544]
it supposedly allows more air to flow down the back glass rather than just flowing straight directing more air over the rear wing (which we don't have, except if you got the factory wing, which isn't functional. . .) worthless mod for a 3, kinda worthless mod for the evo really, although you could argue that at least the evo can reach speeds where this stuff would matter, not to mention actually has a functional wing, most aerodynamic forces depend on velocity SQUARED
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Actually, it is the opposite: the vortex generator causes flow separation, which PREVENTS the air from following the rear window (coanda effect, fluid adhears to curved surfaces) and instead separates off the roofline and hits the high spoiler on the EVO, rather than passing below it. I would actually be worried about REDUCING downforce on the Mazda, since the airflow across the shape of the rear deck is the only thing that gives any downforce to a sedan (I highly doubt the factory "wing spoiler" adds anything other than aesthetics, but the lip spoiler might do a little something).
Either way, I think it looks gross, but to each their own...