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Originally Posted by luxury1
The automatically rising spoiler is a really cool function of the box and definitely makes the car unique but how useful is it especially at lower speeds? I could see that there might be some lift over 100 mph but at 75 it seems a little unnecessary. Does it rise at these somewhat lower speeds to actually combat lift? Just curious...
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Hi,
The Boxster actually gets pretty light at around 75MPH, something like 110lbs. in the rear.
The Spoiler is actually a
true spoiler and unlike a Wing, does not create any downforce to control lift. The difference is subtle, but distinct. The Wing counteracts lift, while a Spoiler prevents it.
Lift happens because of the
Pressure Differential between the Air flowing over the Top and the Air flowing under the Bottom surfaces of the Car. Air pressure under the Car is increased as the Air slows, piling into itself, trying to flow between the Car's underside and the Ground. The Air over the Top on the other hand moves much faster and so has lowered pressure relative to the Air trying to flow underneath. The difference between these two pressures is what causes lift.
By extending the Spoiler, the airflow on Top is literally
Spoiled, that is, it is blocked and slowed down and it's pressure rises to come into equilibrium with the Air flowing underneath, consequently, no lift is created. Wings on the other hand, exert a downforce to counteract the lift created by this Pressure Differential rather than preventing it.
Wings are, at a point, more efficient than Spoilers and so these are preferred for truly high speeds, such as a race Car. Hope this helps...
Happy Motoring!... Jim'99