Disclaimer: This is article is based solely on the authors opinion. The information provided is for general informational purposes, and is not a substitute for professional advice.
If you know me, or read my rants, you would know that mods really aren't my thing, especially when they are "fart cans." However, while some mods can be cool, flashy, or borderline embarrassing, these can actually work against the car's performance in many ways, especially drag coefficient.
Looks versus performance
My second disclaimer is that there are two different categories of mods: Looks and performance. Sometimes, if professional tunes handle modifications correctly, you can actually get a combination of looks and performance which can benefit both the aesthetics and track performance. As mentioned earlier, I was at the San Jose Auto Show today and took a variety of pictures, including some that are in this article. I will do my best to differentiate between performance mods and styling mods.
Phot credit: Mason Bloom
The Chevorlet Camaro ZL1 is a great example of a modified car, yet still delivers performance without drag at high speeds. If you look close enough, the splitter below the grille may have some performance benefit but is likely more for looks, while the rear spoiler is for performance based on the angle and positioning (it looks stock, but with a better view I identified it as modified).
What is drag coefficient?
Car companies, mainly exotic and/or performance ones, tend to make their cars as aerodynamic, and performance-suited as possible. For example, take a look at the picture below of the Porsche 918 I saw today at the San Jose Auto Show.
Photo credit: Mason Bloom
This car has aero on aero on aero and is still stock - as it should be when it has a base price tag of $845,000! Porsche's aerodynamic design limits what is called drag coefficient, or drag. Drag is the enemy of performance because, as is defined, "drag coefficient of an automobile impacts the way the automobile passes through the surrounding air." So basically, when air hits the car it must flow around it smoothly or it limits overall performance. That is why cars such as the 918 are so curvy as those curves allow air to easily pass through and around the vehicle.
Drag is something that should be avoided. When I walked around the San Jose Auto show today, I took a look at many cars to see what company has most drag. Honda, excluding the NSX, was one. Let's inspect this Honda Civic Si closely...
Looks fine, but are those helpful vents or drag in disguise?
Want to see where drag is created? Take a look at the far left and far right section of the bumper in the picture above. What looks like vents to let air through and improve performance/reduce drag are actually solid pieces of plastic. No vents. This creates immense amount of drag and slows the car down...a lot.
Odd mods don't help either
If you've read my articles, you know that I don't like mods in most circumstances because many mods don't actually don't help your car (shocker!). I hate anything that can have a negative impact on performance. When do mods go bad? Take a look at this picture and, before you do, make sure you have some sort of eye protection because in my opinion this is tough to look at.
Some may find this beautiful but these mods make the car so low that air can barely pass under the car! Photo credit: Mason Bloom
I'm sorry but if you are going to modify your car, there should be some performance benefit. I almost had an allergic reaction when I saw the car in the picture above today at The Show. It's bad for your eyes and mine. It's also a crime committed against the performance of this car or yours, if you try to copy it. The more mods added to a car, the less drag created, in a ricer's case. According to Wikipedia, the easiest way to lessen drag is to remove an aftermarket part. Mainly because the less car the less drag, in some cases.
What parts of my car can be a real drag?
You may be surprised. The worst mods to a car include:
-Rear wing: You are reading that correctly. Though the purpose of the rear wing is to create downforce at higher speeds, it can actually get in the way of airflow and create drag if it isn't angled correctly. If a spoiler is angled flat, it can be pointless, because it doesn't create as much of the needed downforce required for stability. It can, however, reduce turbulence, thereby reduces drag. If you want a rear wing for more than just looks, make sure you angle it properly so that the front of the wing is sloping downward towards the front of the car.
-Roof rack: Unless you are driving a station wagon or SUV or just like the look of a roof rack (for some reason!), leave it off as it gets in the way of natural airflow. This can cause turbulence because air is supposed to flow over the wind shield and across the top of the roof, but with a roof rack, the air collides with the rack and creates drag.
-Modified front bumper: One of the most common "looks" mod can actually hurt the car's performance. Which one? No surprise, the modified front bumper. A lot of a car's performance designs begins around the bumper. The manufacturer decides to create a design so air can flow around the car and through the sides. But when someone modifies the bumper without thinking through its impact on the original air flow design, the crap can then hit the fan and everything goes steadily downhill like the Dow Jones stock exchange during the government shutdown. When a modded bumper like the one I saw below creates drag, the air has to find it's way around the car.
How does air even pass through!? Photo credit: Mason Bloom
Yes, drag is a drag. Poorly thought out mods can do more bad than good for a car by creating drag and reducing performance. Drag can take multiple tenths of a second of your car's lap or race time. Sometimes less can be more when it comes to overall performance.