On street cars, they are just copies of race proven aero effect attributes. Front dams do work to reduce drag by decreasing the compressed air under the front of the car; and some rear spoilers, if done correctly, do also reduce drag a little, by reducing the tendency for drag inducing turbulence from flowing back up onto the trunk lid and causing increased separation of the air flow over the rear window.
A minimal front dam is being included on most cars now. And, most cars these days do have a lip of sorts on the rear of the lid to help with that problem. Some even have minimal side skirts which also are effective in a minor way, enhancing the effects of the front dam.
The spoiler on the 164S is not very effective IMO. The rest, to some extent, yes. The 164S Owners Manual does have a chart showing the pressure distribution over the centerline profile of the car at speed, measured I suppose in a wind tunnel with pressure probes, as we used to do with airplane models in a wind tunnel where I worked. Wish they would have included the pressure profiles for the base 164 without spoilers and skirts, etc. You would have seen the difference.
I remember a very old article showing a study done by Alfa on the Sprint GT/GTV body showing how adding a front dam and rear spoiler did significantly reduce the lift and drag on the car at speed. Might still have a copy of that, somewhere, lol.
www.carscoops.com
. I consider skirts and what nots on a road car to be in the same category as touch screens => something we never wanted and makes the vehicle harder to use, with no benefit
