Author: occamsracers

In the world of car aerodynamics, it’s rare to get drag reduction and downforce at the same time. Usually there’s a trade off, where a certain part adds downforce, and with that you get more drag.

Hood vents are one of those magic items that often benefit both drag and downforce; it’s a double win. And because hood vents also aid in engine cooling, that makes them a triple win. Every race car that is allowed to have hood vents should have them. Period.

But what kind of hood vent? There are many products available online, from Gutentight, Race Louvers, Singular, Spiked Performance, Trackspec, and many others. And then there are the DIY options such as stamped steel floor vents from a home improvement store, or 3D printing huge time attack style vents, or simply cutting a gaping hole in the hood. What’s best?

Luckily someone has done a lot of that testing, and provides the data for free. Al Watson of Race Louvers has 27 PDFs on his site, detailing wind tunnel runs on many different cars. I encourage everyone to read those, but I also want to do a deep dive on Miata hood vents in particular, since I race one, and compare his data with my own. Let’s get into it.

Commercial Vents

When it comes to Miata hood vents, the shape of the hood dictates the shape of the vent to some degree. First, because there’s a bump in the middle of the hood that’s difficult to work around, and second, because there are support structures underneath.

Take a look at the following picture of Gutentight louvers installed on a NB hood, and you can see the reason the vents are shaped the way they are; to preserve the support ribs under the hood.

RGR is another company making similar louvers with the same strategy: keep the support ribs. This makes for easier installation, because there’s just a single layer of sheet aluminum to cut through, but it sacrifices some of the venting area.

Is it important to preserve those support ribs? Kinda. The hood is aluminum, and if you delete all of the supports underneath, the skin is too floppy on its own. So keeping some of the ribs makes sense, but you certainly don’t need all of them.

Spiked Performance hood vents require cutting out one of the support ribs on each side. This makes for a larger vent, and is still structurally sound. However, Spiked doesn’t include a vent in the middle of the hood directly behind the radiator. If you’ve read the PDFs on the Race Louvers site, you know that venting directly behind the radiator is the most important area to vent!

Which brings me to Singular, who makes a three-piece louver that’s like the Spiked vents on the sides, but also includes a center vent . It’s a smart design that I tested in a wind tunnel. They worked well, and you can read about that in my wind tunnel report.

If you’re going to keep most of the support structure underneath, that about wraps up the options for Miata hood vents. However, there are some hood vents that aren’t constrained by the OE hood supports, and designed to put as much venting as possible directly behind the radiator. This will provide the optimum performance, but you pay for that twice: more money and a more difficult installation.

Among this variety of hood vents you have products from Trackspec and Race Louvers. For $330, the Trackspec louvers are priced well, but I haven’t seen them in person, so I don’t know how far above and below the surface the louvers extend, and that’s a very important variable.

If you dig into the Race Louvers reports, you can see that the height of the louver is important, and that more is height is better. However, the distance the louver extends below the hood is equally important, and many manufacturers ignore that aspect entirely. So until I get my hands on some Trackspec louvers and measure them, I’ll have to reserve final judgment.

Race Louvers

Which brings me to Race Louvers, and the two types of vents they offer for NA/NB Miatas. The first is a double vent called the XL. Compared to other side vents, these are quite large and universal, meaning not specifically designed for a Miata.

Race Louvers also sells a center vent that can be paired with two smaller side vents. You end up cutting out the center hood bump, and a lot of the support structures underneath.

So how do the vents compare? If you look at the data from Race Louvers, you can see that the triple vent out performed the double vent, with more downforce and less drag. However in radiator pressure differential (which we can interpret as cooling benefit), the XL side vents were slightly better (data not shown here).

Let’s ignore cooling for now and just look at the performance numbers. The double vents made about 25 lbs of downforce at 100 mph, and added two pounds of drag. The triple vents had 35 pounds of downforce the same speed, and only one pound of drag.

Why the difference? Probably it’s the efficiency of the center vent. The most important place to extract air is directly behind the radiator, and side vents just aren’t as effective as a center vent.

Note that more downforce is possible using the taller RX louvers. The louvers Al tested on this Miata were NASA ST/TT 4-6 legal and only 3/8” tall; if your car is unbound by silly racing rules or in NASA ST/TT3 and faster, you can use the full-height RX louvers and gain more downforce.

So how did the Singular triple vents compare to the Race Louvers triple vents? They made almost half the downforce, at 16.5 lbs, and reduced drag by 3 lbs over Race Louvers. That drag reduction is worth about .6 hp, and not a bad tradeoff. Whether you want double the downforce or half a horsepower is up to you, but I would personally take the downforce.

But these were two different Miatas on two different days, and so there may be some minor differences associated with that. Both cars had the same 9 Lives Racing front aero, and I’d guess the variability between the cars isn’t worth a re-test.

DIY Solutions

If you’re more concerned with price than performance, or need to work your hood vents around a custom motor swap, then you may want to design your own. One thing I learned from the JKF Aero course was that you don’t absolutely need louvers, you can make a big gaping hole in the hood, and it actually works quite well. The main problem is a loss in rear downforce from turbulent air exiting the duct, but that can be an acceptable trade for more front downforce.

Hood vents in general have been shown to reduce rear downforce, but it’s less than a 5 lbs at 100mph. It’s unclear how much of that is due to the leverage effect versus dirty air hitting the wing, but in either case, the loss in rear downforce is usually so negligible that you can ignore it.

My Miata has a Hayabusa swap from Spec13, and the engine sits quite tall at the rear of the engine bay, but leaves the front completely open. For an application like this, a fully ducted extractor hood makes more sense than hood vents. Although I will still need vents on the side of the hood to make sure the engine bay itself is cooled, from the heat dumping off the headers.

For side vents, the obvious solution is Race Louvers, but the cheapskate in me isn’t ruling out 3D printing, Amazon shit, or just using a can opener on the hood.

Best practices

The number one piece of advice I can give you is to buy Race Louvers hood vents, they have been designed to outperform every other hood vent on the market, and the data is clear in this respect. For the cheap bastards who DIY their own aero (ahem, my people), here are some guidelines.

• The rule of thumb for hood vent placement is to go as wide as you can, starting the vent 2″ behind the radiator. The vent should extend no further than 20″ from glass in the center, 15″ on the sides. Bigger is better so long as the vents are behind the radiator and not too close to the high pressure cowl area.
• Use louvers that extend both above and below the hood. The larger the louver, the better the performance. Note that if you race in NASA, they complicate the shit out of it. In ST/TT 4-6 louvers are limited to 3/8″ height above the surface of the hood. In ST/TT 2 and below, hood vent size is unregulated. In ST 3, you need to use the ST 4-6 rules if you choose BTM aero, otherwise use the ST 2 rules. Sigh.
• Add a 1″ tall vertical Gurney flap in front of the hood vent opening (although see above if you race in NASA). A taller Gurney adds more downforce, but there are diminishing returns, so stick with 1”. Note that on a poorly designed hood vent (what Al calls time-attack style), a Gurney flap will only add drag, so don’t bother.
• More is better: More height, more depth, more area. Don’t scrimp on the size of the vents.
• Duct the front of the radiator, so that all the air goes through the rad and not around it. You can use canvas instead of sheet metal, which survives crashes better.
• Seal all gaps in the nose. Air that enters the engine bay bypasses the heat exchangers and pressurizes the engine bay. This creates lift and reduces cooling.

If you read Grassroots Motorsports, you’re probably familiar with Andy Hollis’ Triple Threat MX-5 Miata. This is an ND2 Miata that has evolved over time to showcase the benefits of small, incremental improvements to suspension, safety, and brakes, while serving as a test bed for various wheel and tire combinations. These basic modifications enhance performance on track without sacrificing much comfort on the street. I’ve followed this GRM build, this has been much of my philosophy with my ND Miata too – take a simple approach to modifications to have an HPDE and time trial competitive car that can still be enjoyed on the street. 

Having owned several older Miatas over the years, I now strongly prefer mine to have a warranty, cold AC, Apple CarPlay, and 40 mpg fuel economy. I roll up to the track, turn a few knobs, put down a lap, and drive home in relative comfort. For me, I consider this to be the sweet spot for enjoying motorsports in a relaxed capacity. No wheel-to-wheel racing risks. No dedicated race car towed with a truck and trailer. A casual approach with a dual-purpose car checks several boxes, keeping costs relatively low. But when time trial competitors take a more serious approach, sometimes it requires stepping outside of that comfort zone.

When I started running time trial style events at Pineview Run a few years ago, I relied heavily on “cheater tire” mechanical grip and driving my ND1 Miata in a way that only an extended drivetrain warranty and a AAA membership could permit. I didn’t want to potentially sacrifice reliability with additional horsepower and I didn’t want to disfigure stock body panels with lips, vents, and wings.

During this phase of aero reluctance, I still managed to get good enough at the short course to set a class record, win my class, and the overall Challenge Cup series championship for 2021. Pineview (at least in its legacy short course configuration) is a very Miata-friendly track. The past three champions can confirm. 

I’ve since moved back to central Florida and consider the Florida International Rally and Motorsport Park (or better known as the FIRM) as my new home track. The FIRM is a fun and challenging track in its own way, but makes me really miss having some elevation changes. For the most part, the layout favors horsepower, not Miatas.

The main straight is more than three times longer than the one on Pineview’s original 1.1 mile short course. There’s just more speed available to make a strong case for aerodynamic assistance. And that’s what many of my TT5 class competitors have opted for – big wings. When you see these wing-equipped cars running nearly four seconds faster, you realize it’s time to stop being so stubborn about aero. 

At this stage, I had a stiffer front anti-sway bar and a set of Sakebomb Garage tuned Ohlins DFV coilovers – which I give most of the credit for shaping what a dual-purpose ND2 Miata should be. The stock dampers and springs on NDs just make them downright hazardous. The softness can be masked with a good 200 treadwear tire, but quality coilovers absolutely transform these cars. Eliminating the unpredictability of stock suspension allows the car to communicate and quickly inspire more driver confidence and control. If you’ve ever been at a track day and seen an ND do a tank-slapper following some oversteer correction, I’ll bet it was on bone stock suspension.

During pre-season testing at the FIRM, I barely broken into the 1:19s on 15-inch 225 Yokohama A052s. I knew the addition of aero would be necessary to chase some of the faster cars in my class, but I still wasn’t quite ready to start drilling holes in my three-year-old Miata.

In early 2023, I finally broke down and purchased a Nine Lives Racing Big Wang kit. I also found a spare trunk lid on eBay to be the sacrificial new home for the 68-inch rear wing. The downside to this trunk-mounted wing setup is a lack of rigidity due to flimsy hinges, but in the spirit of a dual-purpose street car (and not wanting to permanently draw Fast and Furious style attention on the street), trunk lids with an extra pair of hinges can be swapped in a matter of seconds by undoing four 10mm nuts from the interior of the trunk.

In order to balance out the new massive rear wing, I picked up a sheet of half-inch birch plywood from Home Depot and spent a weekend in the garage building a basic splitter. To be honest, this wasn’t something that I did a ton of research on before just diving in. I would have been content to buy a splitter kit designed to complement the rear wing, but there still isn’t much available in the aftermarket for ND splitters. Thanks to some helpful posts in the MX5 ND Track & HPDE Junkies Facebook group, homemade examples aren’t hard to find and duplicate. For ND owners who track, and aren’t afraid to rub through some fender liners, this is a fantastic community of like-minded members.

The chassis-mounted brackets were constructed with 1×1 inch angle aluminum – the height of which determines the splitter’s proximity to the ground. I targeted around four inches of generous ground clearance on stock-sized 17 inch wheels and tires, but this drops down half an inch when switched to my 15×9 setup.

I gave the splitter blade roughly 3.5 inches of length beyond the bodywork and painted it with some cheap exterior latex paint. I used garden edging and a cardboard-traced strip of 1/8-inch HDPE from Speedway Motors to make an air dam – sealing the gap between the splitter and front bumper that now lacked the OEM Club lip. Overall, this DIY effort is still in the Occam’s Racer D+ grade range, but similar to the trunk lid, it can be quickly dropped with the removal of four bolts. It also helps that it was built for less than $150 in materials. 

The 2023 Time Trial series season at the FIRM was still a struggle to try to get to the front of the pack, especially during the summer with a heat-intolerant tire like the A052. I played with rear wing AOA, stiffened rear suspension to leverage the dose of downforce, and even reluctantly cut some holes in the hood to further optimize my basic splitter.

But after putting it off for so long, I’ve become a firm believer in aero. I initially noticed a slight drop in top end speed, but looking into the data, more than a second was found with the increased cornering speed. 

I’m pretty pleased with the personal improvements made during the season, but the car still wasn’t fully optimized for the TT5 class, leaving some headroom for horsepower, and tire width. I ended up placing third in class overall without doing anything to the stock engine – mostly in an effort to preserve the allegedly fragile manual transmission.

But the FIRM demands horsepower. So for 2024, the car got a header, tune, and full exhaust. The updated dyno numbers didn’t show much in peak power, but looking at AIM data, there’s certainly a slight improvement to corner exit acceleration. I’m still running a 225 tire, but made the switch to a more forgiving RE-71RS.

The FIRM management made the wise decision to avoid scheduling events amidst the blazing summer temperatures in Florida. But once things cool off, there are still a couple more rounds of time trial competition remaining this fall. I believe I’m on target to run my first 1:16 on this combination of aero and a modest 10-15 hp bump over the stock engine. This was a lap that seemed impossible to me a couple of years ago – especially with what I still consider to be a casual approach to track driving, data coaching, and aerodynamic “development.” 

To summarize my rudimentary introduction to aero: a little bit goes a long way. It’s certainly a slippery slope, but you don’t need to run some wind-tunnel-perfected setup on the first pass to see significant results. My Miata still has a basic, user-friendly aero-on-demand package.

Could it go faster with more expensive, race-focused improvements? Totally. Do I want it to become a car that loses streetability and lives on a lift or trailer? Absolutely not. Maybe this is an easy stance to take on a car that still has less than 30,000 miles on the odometer. Perhaps I can get away with drilling a few more holes while retaining a reasonable trade in value. But in the meantime, I’ll keep enjoying the best of both worlds. 

This tire test starts with a rant; bear with me for a minute while I get this off my chest.

Once upon a time, treadwear (UTQG) meant how long the tire would last. A 300 TW tire lasted longer than a 200 TW, which in turn lasted longer than a 100 TW. Grip was inversely proportionate to wear, and so 100 TW tires gripped more than 200, which gripped more than 300. Makes sense, right? Wrong. That ship has sailed, and it ain’t coming back.

These days treadwear values are total bullshit, especially in the popular 200 TW category. Back when treadwear meant something, honest 200 TW tires, like the Falken RT615k, Nitto NT05, Yokohama AD08R, and other similar tires lasted 20+ hours on track, had good heat tolerance, and respectable speed. Crap can racing series like 24 Hours of Lemons and Chumpcar standardized on the 200 TW tire, and you could chose any of them with relative fairness.

But the landscape completely changed when autocross-specific tires came out, such as the RE71R and Rival 1.5S. Like endurance racing, most autocross classes also require 200 TW tires, but with only half a dozen 45-second runs per day, durability didn’t matter. So the autocross “Super 200” tires were developed and became a completely different animal than any 200 TW tire that came before.

Because autocross is a competition, every autocrosser wants the fastest 200 TW tire. And since treadwear values are set by the manufacturers, they can take a domestic 140 treadwear tire, write 200 on the sidewall, and sell it in the USA as such. And thus began the idiotic 200 TW tire wars where tires got faster, less durable, and the treadwear number remained the same.

The result of that is you can buy a 200 TW Falken 615K+ that last two to three times longer than the 200 TW Falken 660. Bridgestone, Nankang, and Yokohama also offer an endurance 200 TW tire that lasts three times longer than their 200 TW autocross tire. And yet they all have the same treadwear rating. So much for treadwear meaning anything about wear.

So does 200 TW mean there are now two classes of tires? No. Because there are also tweener tires like the Kumho V730 and Nexxen Sport R, which are part way between an enduro and autocross 200. And then you have Accelera, Kenda, and Valino, who offer bargain 200 TW tires that are slower, but cheaper, than the enduro 200s.

Which brings me to a brand new 200 treadwear tire, the Armstrong Blu Trac Race. It’s certainly a bargain 200 TW, but I was curious to see whether it was also an autocross or enduro 200 TW. Or something else.

Armstrong Blu Trac Race

You may not have heard of Armstrong tires; I hadn’t. They are available through Tire Streets, who deal in lesser know brands, mostly from Indonesia, I believe. If you are in the drift community, you know Accelera tires, which are the official tire of the LZ World Tour. If you’re outside the drift community, you may not know Accelera or Armstrong or Tire Streets.

I ordered the 235/40r18 size, which were on sale for $135 each, shipping included. This is about half of what most 200 TW tires cost, and so you can see we are clearly in the bargain 200 TW segment.

The first thing I noticed about the Blu Trac is that the tread pattern looks a bit like the venerable Nitto NT05. There are two very wide center grooves, and a symmetrical tread pattern, so you can flip the tire on the rim and get a little more life out of them.

When new, they give off a low whoop-whoop sound like a helicopter. I found a resonant frequency at about 35 mph that was uncomfortably loud. But once the tires wore down some, the sound level went down to where I stopped noticing them entirely.

But the street is no place to test a track tire. To properly evaluate them, I’d need to take them to a racetrack, record lap times and G forces, and compare them to a known quantity. Before doing that, I heat cycled them with a few laps at Pineview, and let them sit for 24 hours.

Kumho V730

To see if the Blu Trac were any good, I compared them to Kumho V730s. I’ve been using the V730 recently, and I feel they set a new standard for track tires. I used to feel that way about RS4s, but a ridiculous sale price on the Kumhos got me to try them, and the gain in grip is an acceptable tradeoff for increased wear.

The V730 tread pattern isn’t symmetrical, and is similar to another ancient Nitto track tire, the NT01. Now there was never anything wrong with the NT01, and I think Nitto could have written UTQG 200 on the sidewall and nobody would have blinked.

V730s are well regarded in the track community, and inhabit the tweener space between autocross tires and enduro tires. The smaller tread grooves disappear quickly, leaving two off-center groves that could be mistaken for a Maxxis RC1. Like the RC1, these won’t work well in the rain. But I have other tires for that.

Pirelli PZero PZ4

To make this more interesting, I’ll also throw in a set of Pirelli PZ4 tires, which I bought specifically as a wet tire. The Veloster N originally came with PZ4s, and most comparison tests put them on par with the Michelin PilotSport 4S and Continental ExtremeContact Sport. The PZ4 is rated at 280 TW, and is not a dedicated track tire. It’s a good street tire, OK on a dry track, and great in the wet.

Track testing

For tire testing I go to Pineview Run, mostly because I’m a member and can go whenever I want. It’s empty on weekdays, so I can run as many laps as I want. They run a much shorter track during the week, and so I can get a lot of laps and normalize the data.

I use a pyrometer to properly set tire pressures, and bleed them down to get an even gradient, slightly hotter on the inside. I use an AiM Solo DL for lap times and data gathering, and then convert the lateral Gs into a CSV file. This way I can average the various peaks and valley, to find a more stable lateral G value.

I did the testing over two days, doing back to back runs an hour apart. Pineview runs their track sessions on the hour, and so I couldn’t get sessions any closer than that. However, weather conditions didn’t change much, and so I don’t think that was much of a factor.

All of the tires were mounted on 18×8.5” wheels. The Kumho tires were mounted on Koenig Countergram +43, and the Pirelli and Armstrong tires were mounted on Motegi MR140 +45. The wheels are all within half a pound of each other, and I feel the offsets are close enough that the differences will be down to the tires themselves.

But note that I also threw in a mismatched set of tires, to see how the V730 front and PZ4 rear would work. I reckoned that less rear grip would allow me to rotate the car easier, and perhaps set the fastest time. But it didn’t.

The fastest lap was the Kumho V730 all around, going about four tenths faster than the cocktail with the PZ4 on the rear. The handling with mismatched tires was a little too loose for my tastes, and I even spun the car once with the Pirellis on the rear.

With the PZ4s front and back, I went .8 seconds slower than with V730. People love to hate the PZ4, but it’s not a terrible tire. Compared to the V730, the PZ4 is noticeably less sharp everywhere, but especially on turn in.

Which brings us to the Armstrong Blu Trac Race, which where 1.2 seconds slower than the Pirelli PZ4, and a full 2 seconds slower than the V730. On a longer race track with a more typical lap time of 90 seconds, Blue Trac Race would have you 4 seconds off the pace of the V730.

If you look at the following speed trace, you can see where the Blu Trac (blue) loses out to the PZ4 (red) and V730 (green). Blu Tracs have a corner speed that’s similar to the PZ4, but I’m consistently later to throttle on these tires, which results in a lower top speed. The Kumhos have more grip and allow me to maintain a higher minimum corner speed, which results in the fastest lap times.

But let’s talk about how the tire feels and wears. I really like the way the Blu Trac Race tires break away early, and are predictable when sliding. I often use all-season tires for hooning, and the lateral Gs of the Blu Tracs are similar. The difference is, Blue Tracs have fewer grooves and wider tread blocks, and these combine to make a really friendly tire that begs to be driven sideways.

Pineview has a rough surface with a lot of right turns, and so the left tires get a lot of abuse. My Veloster is front-wheel drive, and the combined braking, accelerating, and turning with all the weight on the nose absolutely murders the front left. As such, I ruined my Pirelli PZ4s in just seven 15-minute sessions. I had bought them for rain use, but the forecast was wrong two Wednesdays in a row, and I ended up eating the tires before I got to use them in the rain.

Conversely, I ran eight sessions on the Blue Trac Race tires, and they are wearing superbly. They certainly have the durability to last an endurance race, but you’d be well off the pace of everyone on RS4s. However, there’s a better use for Blu Trac’s than racing.

The best HPDE tire?

I started this article by wondering if the Blu Trac Race was an endurance 200 or a Super 200. But what I found out was, it’s neither. It’s a HPDE 200. Yeah, that’s right, I’m starting a new category of 200 TW tires, and I’m putting the Blu Trac in there at the top.

HPDE stands for High Performance Driving Education, and if you want a tire that is exceptional for learning how to drive, this is your tire. The lower grip, predictable breakaway, and durability combine to make a tire that is perfect for the E in HPDE.

Armstrong Blu Trac Race tires are not going to win any timed competitions. Full stop. But they will help you learn how to drive your car at the limit, because the limit is lower, easy to find, and easy to recover when you invariably go over.

My Veloster N is a well balanced car that doesn’t know it’s FWD. In fact it pushes less than many RWD cars. I can pitch it into a corner and get a four wheel drift, easy-peasy. Ergo, driving it on tires that have less grip is actually more fun. No tire has put such a big smile on my face as the Armstrong Blu Trac Race.

At the end of the session, many people came up to me to tell me how fast my car looked (because it certainly wasn’t fast on the stopwatch). And I think this was down to the car sliding everywhere, and just how loud the tires are. See and hear for yourself.

In the following video, I do some laps in front of and behind a Mitsubishi Evo X. He’s got a 400 hp tune and Kumho V730 tires; I’m 130 hp down, driving a stock Veloster N, with Blue Trac Race tires. I point him by part way through the session, and I’m able to keep a similar pace. So a decent driver can wheel the shit out of these tires and run with faster cars on better tires. And have more fun in the process.

Note this is on the shortest track layout at Pineview, which is about 6 seconds faster than the lap times in the previous table. To learn more about the track, see Pineview Run Layouts.

If you appreciate articles like this, and websites with no ads, no pop-ups, or other annoying shit, consider buying me a coffee. Thanks!

As a follow up to the previous post, I wanted to see how much aero was worth at various race tracks. To do this, I’ll build a Veloster N at three stages of aero development, and see how they compare in OptimumLap. Let’s call these aero packages OE, Sport and Track.

OE aero is simply the car as delivered. If you read my wind tunnel report, you’ll know the coefficient of drag is .421 and the coefficient of lift is -.027. The drag is higher than you’d expect, and the fact that the car makes a little downforce straight from the factory is remarkable.

Sport aero consists of parts you’d drive on the street, so I’ll add lowering springs, but not a splitter, because that would take damage on driveways. I’ll add top and bottom canards to get more front downforce, and I’ll balance that out with a wicker/kicker on the spoiler. Wind visors worked really well on my VN, so let’s add those, too. Given these modifications, we have a car with around .50 drag and -.50 downforce, not bad.

The more extreme aero kit I’ll call Track aero, and this is my curved splitter and a wing, plus hood vents. I’ll keep the canards as well, and this brings the drag up to an even .60 and downforce to 1.00.

I’ve tested all of these parts in a wind tunnel, and so the drag and downforce numbers are accurate to within a couple percent, even though it looks like I’m just choosing round numbers. To compare lap times on each aero build, I’ll throw them all into Optimum Lap and see the time deltas for different tracks. In the following table, the numbers represent the time advantage per lap versus the OE aero.

From this you data you can see a couple outliers, and the most obvious is VIR. Sport aero was a .7 second advantage over OE bodywork, but Track aero was only .3 seconds faster. Meaning, you’d go faster with the Sport aero than Track aero! This is the only track where this is true, and so drag is obviously a dominant factor at VIR.

Drag also plays significant role at tracks like Watkins Glen and Road America, and coming up with an aero package for these tracks is more challenging, because you really need to strike a balance between drag and downforce. Knowing exactly how much downforce and drag each part makes is essential, because then you can just put the numbers into OptimumLap and find out which aero will make you fastest.

On the other end of the spectrum are tracks where cars spend most of the time cornering, which makes it quite easy to design a car’s aero: add as much downforce as you can, and ignore drag completely. For example, at Palmer, the big aero build goes a full second faster than the medium aero build, which in turn goes 1.3 seconds faster than OE aero. That’s 2.3 seconds in your pocket from aero alone, that’s awesome.

That same strategy can be used for any race track where there are shorter or fewer straights, and more corners. And so Canaan, and Club Motorsports, Pineview’s various layouts, and Waterford are also tracks where you’d go after as much downforce as possible, and completely ignore drag as a matter of any consequence.

In the middle of these extremes are most of the race tracks in the USA, which have both fast and slow sections, but not too much of either. Tracks like Gingerman, Lime Rock, Mid Ohio, NYST, Summit Point, and Thunderbolt come to mind. At these tracks, the lap time delta between Sport and Track aero is around 160%, and for the most part, you can again ignore drag and go after as much downforce as possible.