Project “My Fiancée’s” Miata: Part 11 – How to add a Professional Awesome Splitter, an APR Performance Wing, and Improve Your Lap Times

Up until now, this project has been about making the car more reliable and safer at the track, but not much faster. We all knew that had to change eventually. The time has officially come to start increasing the performance capabilities of the fiancee’s Miata, but we’re going at it differently than most, by focusing on aerodynamic gains to start with! A lot of people will tell you that lower power/lower speed cars don’t really benefit from aerodynamic gains, but I’m going to say right now, that if you’re on a track, adding downforce and/or removing drag will have big benefits, even if you’re making less than 100whp. As most of you know, occassionaly, I drive for Professional Awesome Racing and we’ve been developing aerodynamic goodies. Now is the time to put them to the test. Read on as we add a front splitter, front diffusers, and a rear wing from APR Performance to round out a nice little aero package for the nice little Miata.

Our lovely Miata, basking in the sun, shows why it has terrible aerodynamic properties. Notice the front tires completely exposed to the oncoming airflow. Rotating tires are extremely inefficient aerodynamically. Combine that with the monster truck ground clearance that allows for a ton of air to get jumbled up by the rough underside of the vehicle and you have a draggy mess on your hands.

To begin with, the NA Miata is a prime candidate for aero upgrades, because the aero from the factory is pretty terrible. Pretty terrible is a great starting point, because it leaves lots of low hanging fruit ready to be plucked for improvement. To start with, convertible cars in general are notoriously draggy. On top of that, the Miata has its front tires exposed to a lot of oncoming air and the ride height is huge. This all adds up to a coefficient of drag in the .38 range. A Prius’ coefficient is .24, a Lamborghini Countach, which is said to have the aerodynamics of a barn door, is .42… that the Miata is that close to the Lamborghini isn’t something to brag about. That being said, the Miata does have a relatively small frontal area, which helps, but the poor drag performance gives us plenty of room to make improvements.

So how do we improve the car? One of the biggest gains would come from having a hardtop, with a fastback shape, but we don’t have those kind of funds. Instead, we’ll start at the front of the car and keep air from getting under the floorpan, as well as stopping the air from running into the jumbled aerodynamic mess that comes from spinning tires. You can do this two ways, with an air dam, or the big boy route, with an air dam AND a splitter. An air dam can reduce lift and drag, but the addition of a splitter gives the benefit of barely increasing drag and piling on a nice scoop of downforce. Which way do you think we went?!

Installing a splitter isn’t the easiest job in the world, but one that can be tackled with a few friends and a weekend or so of time. There are plenty of material options to choose from such as plywood, carbon fiber, ect… but we are using Alumalite, which is a corrugated sign board material. We at Professional Awesome having been using Alumalite for years and developed a “universal” pre-cut design out of the 6mm thickness variety.

We get started on our splitters by using wood to establish a ride height for the blade. Lower is generally better… until you smash your splitter into the ground.

When designing your splitter system, step one is determining at what height your splitter will be running at. The lower the splitter, the better it will perform (until it’s exceptionally low), but the more likely you are to run it into the ground and damage it. We settled on an approximate starting point of 3” of ground clearance. This is a fairly standard height for vehicles with fairly stiff suspensions, which the Miata does not have, but the Miata won’t be going very fast, so we thought it was a safe choice. More on that later.

The centering process of your splitter is frustrating when you realize your 30-year-old car wasn’t built perfectly symmetrically. We get it good enough for who it’s for.

 

Another critical aspect is to get the splitter clear of your tires when they turn, compress, and droop. Don’t forget this important step, unless you want to cut up your tires and/or rip off your splitter.

2 comments

  1. Massive congrats on upgrading your fiancee and your car! It’s nice watching the car progress from girlfriend’s Miata to wife’s Miata.

  2. Congratulations to you and yours, good sir! Looking forward to seeing what you two decided on, I’m sure it will make for excellent reading material!

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