The splitter produces down force, as it's name implies, it splits the airflow, sending most of it upwards And over the car, and the remainder under it, there by forcing it to increase in speed and lowering its pressure, splitters have been found to work very well at fairly high ground clearance, this makes them more benign and can incorporate a diffuser, unlike a NASCAR splitter which precludes all airflow under the car, but are far from benign for that reason, take off is not uncommon, also these don't use rear wings for reasons of racing purity, just a controlled spoiler, side skirts are not necessary on any car, modern flat bottomed skirt less cars produce huge downforce, a curtain effect is caused by simple physics, low pressure air can't bleed off into high pressure air, plus a boundary layer forming additional curtain effect that can be controlled by the lucky few with wind tunnels, most old Skool ideas have been debunked these days, side skirts and such, and new ideas prove wings can work without too much drag penalty for LOW SPEED work, say at or below about 85 mph, slaloms for example, now here's the rub, the effective wing angle can be up to 35 degs, not the 14 or 15 of the old theorists!
it was obvious last F1season that redbull ran at higher rake angles and ground clearance than most others, indicating they had downforce in hand and were using more rear ride height for other reasons, possibly rear weight transfer, side to side or to the front, or for kerb riding ability, lucky them..
As ever, the trade of is drag and weight, how much extra power do you need to pull it all to a faster lap time, non if it's well thought out and shows on the watch over a race distance, if it's faster over race distance, say 10/15 or more mins', it works.
Road cars have no datum, unless you go to a race track and time test before and after, you can't just say " that feels better", better for what? Speed? Fuel consumption? Passenger comfort? That's the problem with road cars, the right tyres and wheels and good brakes are a better bet for development with these, and good looks for the girlies of course...
