A car needs to be well-balanced to perform properly on a track. Spoilers were introduced to provide downforce in cars to improve their handling and prevent them from taking off at very high speeds.

So deciding whether you will need a spoiler depends mainly on your use case and your car’s limits.

Generally, spoilers are also added to exotic sedans just to add to their looks. It doesn’t do any good at managing the aerodynamics of the car or providing any downforce. Adding a beefier spoiler to your family sedan can just result in increased drag, which can result in even worse fuel economy. But manufacturers also consider adding them to some of their sedans at sports trim, just to make it look racing-oriented and to improve their aesthetics.

A spoiler’s role comes into play at high speeds at about 150 to 300+ kmph. A car generates an amount of lift at high speed, so to restrain it from taking off at high speed, spoilers provide sufficient downforce to keep the car pushed onto the road. Spoilers are deployed to provide the car, with an added normal force, which increases the frictional force between all tires, which can help it steer into sharp corners at even higher speeds.

Spoilers are considered unnecessary in front wheel drive vehicles, but they also play a major role in them. A car without spoilers, generates greater downforce at the front end, just due to the geometry of the bonnet, fenders, and windscreen. It helps bring the car’s center of pressure, i.e., the effective point of action of downforce, to the middle of the car’s body. This prevents cars from oversteering in corners at high speeds.

Spoilers also help in providing improved braking at high speeds, just due to the additional downforce at the rear end. Generally, when brakes are applied, a car’s momentum is shifted towards the front end, but a spoiler can allow increased braking at the rear end, to ensure stability and shorter braking distances.

If your project car has the potential to reach high speeds, such as around 250 kmph, and other components such as its suspension, braking, and tires can keep up with the car at such high speeds, you can add a well-engineered spoiler to it to get extra stability at higher speeds, especially on tracks.

But if your car’s components aren’t meant to withstand high-speed maneuvering, then it will need a lot of other upgrades before you think of attaching a working spoiler to it. Also, you can add a considerable spoiler that matches your sedan’s look just to give it a sporty look if you’re into that kind of thing.