Tail spoiler lexia distinction

First, let's rule out a misunderstanding, not all lexia of the rear wing mounted on the rear of the car, things are as shown in the following figure this kind of thing is spoiler. The car is a Chevrolet AVEO, are housed in the price of many small fastback car spoiler instead of tail. As shown, the rear of the car to do it prominence is like a duck tail spoiler red roof down airflow block, to form a downward force. The spoiler can also be effective in reducing the high speed when the upper buoyancy, but its effect is completely different principle and tail.
Simply put, the tail is designed in order to reduce the buoyancy of the high-speed traveling. First to simply talk about the buoyancy of the causes. The figure is a schematic view of the vehicle at high speeds, and if the air as something tangible, the car in a high speed car front air will be divided into two parts, the part from the upper part of the vehicle through, in part from the lower part of the vehicle through.
 
The tail is the just described process reversed, made of lower stroke length, the short stroke of the upper structure, so that we can obd2  obtain a downward air flow the pressure (negative lift), offsetting the vehicle lift. And now, most of the sports car with rear-wheel drive, tail provide negative lift just acting in the rear of the vehicle, to enhance the stability of the vehicle and increase the grip is very good.
So we are clear, although the help of high-speed stability, tail spoiler essential difference: the tail to provide a negative lift, spoiler not have this feature.
In fact, the car at low speeds, the air car is small, the tail of the role of little, smaller car (car less than 2.0L) fitted the role of spoiler, installing a tail seems very heavy. Only when the speed of your car often more than 90KM / h, when air resistance significantly affect the car's driving performance, mounted the aerodynamic package significance to reflected.
In fact, the car at low speeds, the air  uobd2  car is small, the tail of the role of little, smaller car (car less than 2.0L) fitted the role of spoiler, installing a tail seems very heavy. Only when the speed of your car often more than 90KM / h, when air resistance significantly affect the car's driving performance, mounted the aerodynamic package significance to reflected.