The Secrets of IndyCar Aero Kits

There are secrets lurking on every surface of the new IndyCar aero kits. Be they flicks, or bumps, or whisps, or gaping holes. This is an explanation of how they all work and why they may just be enough to convince you to pay attention. Plus, there's lots of pictures of race cars in here!

It's once again time for IndyCar to take a stab at reinvigorating their sport, revitalizing their fan base, and drawing new viewers to venues and TV screens everywhere. (Except Brazil, of course.) And that means NEW CARS! Or, you know, just new aero kits.

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And you might as well be inclined to say "just new aero kits", but you'd be selling the changes very short. As far as IndyCar goes, this is the day 350 million years ago when a fish crawled out of the ocean and decided to be a lizard, or a bird, or a horse or whatever. They have evolved in the name of improvement and transcendence, and now they must race!

Before .........................................................................350 Million Years After

Or am I going too far? Well, that depends on how you look at it, or if you look at it. So, let's look at it!

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BUT WAIT - not before Slipstream Podcast gets their due. They are the brains behind all of this content. (And on that some token, they're responsible if it's all a bunch of bull! I kid.) You should Subscribe to their podcast, rate it (5 stars), follow @SlipstreamPOD on twitter, and head over their Kinja page to stay abreast of what they're up to.

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I never knew so much about what was going on in these new aero kits until I listened to Aaron Foster and Dusty Michael break down the details. And because Aaron is a real aerospace engineer, he speaks the truth. So there. The rest of what is contained herein is pulled largely from Episode 26, and you should go listen to that now.

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So...how did we get here from there? I thought IndyCar was a spec series?

Well, I'll tell you how. In previous years, the IndyCar rulebook (which is graciously published online for all to see, unlike NASCAR...booo!) prescribed nearly every aerodynamic surface with only some room for adjustment. As teams became more limited in how they could manage airflow over the car, IndyCar grew essentially into a spec series, and not one that fans were flocking to support.

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(Airflow under the car is due to the shape of the floor, and that is still prescribed by the rules though it does undergo one noteworthy change this year. More on that later.)

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"Spec series!? Come on! They're NOTHING alike! That one says Snapple!"

So to address that "spec series" stigma, IndyCar has handed this air management over to the engine manufacturers with the possible expectation of bring more engineering and innovation to the forefront and creating a truer test of man and machine. And, you know, hopefully making it way more exciting to watch!

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How IndyCar went about this was to essentially say to Honda and Chevy, "Look. There's is an invisible box around the front wing, an invisible box around the side pods, and an invisible box around the rear. Build whatever aero kits you want that bolt onto this car and that still fit inside those boxes." With that, the engineers were let loose with their slide rules and calculator watches, and went wild within the confines of a few tiny boxes. Works for me!

Okay, so engineers in tiny boxes. But what am I looking at?

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That's a bad photoshop, right? Right? It has to be.

Well, broadly you're looking at three regions where air is being manipulated over the car, and one area of compromise in the form of a change to the floor of all the bodies.

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Three regions and one compromise.

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Seen here on the Honda, the three main areas where changes were made are (1) the front wing, (2) the side pods, and (3) the "rear". The front wing is fairly straightforward as far as knowing what we're talking about. The side pod includes the radiator tunnel, and also incorporates the "sponsor blocker" (so called for "blocking the sponsor logo" when viewed at eye level). Calling the third area "the rear" is more out of ease than as an accurate description. The rear really refers to everything behind the driver from the engine cover to the rear wing and bumpers.

One compromise common to all cars, and one that eluded me until Slipstream pointed it out, is the gaping hole between the radiator tunnel and the sponsor blocker. Look below at this "floor" on the old DW12 (right) and the new hole on the Honda (left). The story goes that this solid floor is worth around 300-400 pounds of downforce(!) and that these new aero kits may be good for around 1000 pounds of additional downforce! Seeing as this is a LOT of downforce, a compromise was necessary somewhere. Cutting out that relatively small hole from between the blocker and the tunnel was a way of dialing back some of the incredible gains expected from these new aero kits. I could just be easily impressed, but those are some amazing numbers!

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The previous DW12 of those badass winners over at CGRT. And a Honda.

But more specifically than front, middle and rear, you're looking at wings and humps and bumps and probably wondering what it all does. Unfortunately, "what it does" cannot be answered all at once because Honda and Chevy dreamed up two wildly different ways of manipulating air to their will. So answering that will require two explanations, and to do that we'll have to take each kit from front to back. Aaron and Dusty from Slipstream - they will be our guides.

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But before that, one note about the engine: though all IndyCar engines are 2.2L twin-turbo V6s with around 550-700 hp (configuration depends on track), Chevy has traditionally made better use of that power than Honda, and that fact may inform some of the decisions seen here. And with that, we're off!

CHEVY: Aerodynamics Aaron says: "I...[as a genius]...see the Chevy kit...and to me it looks that they tried to focus more on reducing drag."

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Aaron goes on to explain how the (enormous) rotating tires create (enormous) aerodynamic drag and (enormous) turbulence. Blah, blah, math, math, etc. All you need to know is that giant spinning tires produce a LOT of turbulence and air should be kept away from them at all costs. (Or something.) From front to back, this seems to be a large part of Chevy's design.

Front Wing

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As Aaron points out, the purpose of the many elements of the front wing appears to be moving air over and around the front tires, simulating the presence of a front bumper. The most interesting element, and likely the key element, is the raised winglet that works in conjunction with the upper portion of the sculpted endplate.

Without that winglet, the air traveling up that endplate would simply be ejected upward, creating considerable turbulence that would go on to affect the aerodynamics of the many surfaces and elements along the rest of the car. Instead, the raised winglet is introduced ahead of the endplate in an effort to manage that turbulence.

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The winglet creates a ribbon of smooth, fast moving, low-pressure air (red) just above the sculpted endplate. As air is ejected from the endplate (yellow), that air merges with this low-pressure ribbon. The combined effect is the air ramping off the endplate, merging with the smooth low-pressure ribbon and then arcing over the tire undisturbed.

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The remaining wing surfaces achieve a combination of downforce and air smoothing around the tire and nose. The suspension components also contribute to smoothing the air between the wheel and the nose before it goes on to encounter the rest of the body.

SIDE POD

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Returning to Aaron's expertise, he points out that these side pods appear to be designed for drag reduction, accomplished by shaping the turbulent air into smoother flowing air before that air reaches and interacts with the surfaces at the rear. One glaring issue to contend with at this portion of the car is the aforementioned and elegantly named (by me) "gaping hole".

That gaping hole, as you'll remember, is a compromise, and one result of that compromise is a "crap ton of turbulence" created by air escaping from underneath the body. (Since Aaron is a trained professional, I am quoting his technical language here.) With turbulence being the enemy of speed, that crap ton must be sorted out. The solution appears to be strong-arming that dirty air into being nice smooth air by confining its travel to between the sponsor blocker(s), along the surface of the side pod, and beneath the upper flick.

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The side pod of the Chevy aero kit has earned quite a bit of criticism for being "ugly" and perhaps unsophisticated, and the flick protruding from the side pod seems to be the worst offender. While that may be true - it may be visually jarring, the problem it's designed to address is an inelegant one, and the solution seems commensurate. If pummeling the air into submission creates positive results at the cost of aesthetic, then count me among those that couldn't care less what it looks like. There are no points awarded for beauty, so move on.

Whether we see results, though, will depend on whether Chevy's solution for the rear end of the car works out.

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REAR END

This is where all the hard work up front and down the sides comes together. The ultimate goal of the front of the body is allowing the remaining rear aero bits to perform their functions to the best of their abilities.

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The upper flick (1), as explained, smooths the air before it reaches the bulge and main flick (2) ahead of the rear tire. The bulge/flick (2) is intended to address the same issue as with the front wing - to move as much air as possible around the spinning tire. The bulge acts in a similar manner as the winglet up front, accelerating the air before it passes over the tire, thus extracting and smoothing turbulent air from off of the tire. Behind the tire, the top flick/tunnel (3) and the bumper pod (4) further smooth the exiting air to reduce drag.

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The additional surfaces in front of the rear tire (5) along with what appears to be a tunnel curving around the side pod and inboard of the rear tire, accomplish the feat of moving air around the rear tire.

Finally, the main event of any IndyCar in my opinion, is the multi-element rear wing. In previous years, as mentioned above, the rear wing was prescribed and included a single primary element (the flatter bottom piece) and a single secondary element (the angled piece above the primary). (See the 2014 cars above). This year, manufacturers are permitted to incorporate their own designs for managing airflow over and around the wing. In both cases, the result is a more efficient and aerodynamic multi-element rear wing and, in Chevy's case, vented end plates.

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This is where Chevy pulled the most from Formula 1 and, as you might have guessed, did so in the name of reducing drag. To begin with, the secondary element (6) is now made of two pieces. Without knowing what degree of adjustment might be allowed here, we do know that this design is going to allow more air to escape through the secondary element and produce far less drag than the previous years' single-piece secondary element. Furthermore, the vented end plates (7) will allow air to escape from the sides and result in less air moving more slowly over the top of the wing. That, along with more air moving faster beneath the wing, results in more downforce without creating too much additional drag.

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There are, of course, implications form all all of this. First, however, let's take a brief look at Honda who have employed a possibly simpler, though perhaps more esoteric, strategy.

HONDA: Aerodynamics Aaron says: "It comes as no surprise that you see a lot of F1 experience in this Honda aero kit design."

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Honda contracted with Wirth Research - the designers of the 2010-2012 Marussia F1 car, and so there's no surprise that certain details from the Honda aero kit are reminiscent of features now common in F1. (Wings. Cough cough. Lots of wings!)

Front Wing

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The name of the game here - and indeed throughout the rest of the body - is downforce. As Aaron point out, there are numerous very small and very specific components that contribute to the overall design of this wing, thus revealing its F1 heritage through Wirth Research.

If you begin by breaking the wing up into the ends and the middle, it might at first appear that Wirth failed to "spread the wealth", leaving the middle of the wings comparatively bare. As it turns out, there may be a reason for this. (Who knew!)

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With formidable downforce comes formidable drag, and this front wing looks like it produces formidable downforce. In a possible effort to reduce some of the overall drag produced by the aero kit as a whole, Honda designed smaller radiator openings and thus a narrower, sleeker profile.

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The bare middle section of the wing, therefore, is designed to cope with the smaller radiator openings. As Aaron explains, there is nothing on the wing to "bar any kind of entry [of air] into the radiators" and nothing to "trip the [air] flow into turbulence".

Whether the wing necessitated the radiator opening, or the radiator opening necessitated the wing, the result is the hallmark of the Honda aero-kit - the so-called "wings on wings on wings (on wings)". But that title also leaves out the very prominent endplates on said wings.

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Here's Aaron: "When you get to the tips of a wing, . . . the air is going to want to swirl from where there is higher pressure to lower pressure. So what these end plates end up doing is preventing all of the higher pressure air over the top of the wing from swirling down underneath." What remains to be seen is whether the apparently lopsided - both front to back, and side to side - design will cause the wing to flex under extreme pressure.

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Side Pods

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The side pod issue on the Honda aero kit is a boring affair, at least relative to the Chevy. This could come down to how air is managed at the front of the car, necessitating fewer "solutions". It could also come down to the overall aero kit strategy as Honda is clearly in the downforce corner while Chevy is in the low drag corner. Regardless of the differences, both manufacturers have to cope with the gaping hole.

While Chevy employed their flick, Honda's winglet behind the sponsor blocker appears to accomplish the same goal of smoothing out the turbulence. Honda seems to be accomplishing from below what Chevy accomplished from above.

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Or will Chevy stick with the flick? Scott Dixon's car, below, may beg to differ.

Rear

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Again, going back to the F1 heritage via Wirth, one of the most prominent features of the Honda rear is the shark fin on the engine cover and behind the driver.

According to our resident expert, Aaron: "When air is escaping a [aerodynamically challenged] body [such as the driver's canopy], the flow from one side to the other takes turns generating these massive vortices. The further you can push that point back and try to smooth the shape out, you can ultimately prevent that from happening, . . . and you can prevent throwing that turbulence over the rear wing." Clearly this was designed to deliver the cleanest air possible over the rear wing.

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Additionally, instead of the flicks and bulges designed to usher air smoothly up and over the tires of the Chevy, the Honda is replete with wings both in front of and behind the rear wheels. And the goal of maximum downforce continues.

The theme of the Honda is downforce, and the tone of the Honda is simplicity. Ignoring the front wing - if you can do that - the rest of the Honda is a fairly straightforward and occasionally dull sight. There's a wing where you might expect it, there's not where you wouldn't. It's enough to wonder what Honda has up their sleeve. As a fan, I'm in deep with Chevy and I'm alway rooting for the ladies and gentleman at Ganassi. But this Honda kit gives me serious pause.

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So what does all of this mean for racing?

Well, for starters the point behind introducing these new kits has always been to inject new life and new variables into the sport.

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For racing in IndyCar, it means that there's no going back to the way things were. The only way is forward. IndyCar may remain the more "primitive" top-tier open wheel series, but that's not for the worst. Formula 1 is what it is. IndyCar does not need to be that as well. For everyone that says that F1 had become too technical, they should be reminded that there is a series where the drivers still drive the cars. (I'm actually talking about NASCAR now, but you get the point.)

Whether you like this kit or not, it should at least mean to the race fan that IndyCar is ready for the next chapter. And if nothing else, it means a bunch of untested tech on track while drivers, teams, and manufacturers attempt to figure it all out over the course of a season.

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So these aero kits are new and "untested". What issues can we expect?

Well as Slipstream points out a couple of times, the obvious question from all of this downforce on the Honda is whether the mounting positions of the front and rear components and the structural integrity of the wings can hold up. Will the kit remain rigid, or are we looking at another Red Bull front wing or Toyota rear wing?

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The IndyCar rules prohibit "devices that are movable or adjustable while the car is in motion" or that "may affect airflow or aerodynamics" - Rule 14.6.2, so the potential for serious penalties is certainly there.

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Furthermore, consider the overall purpose of the Honda versus the Chevy. While the Honda is gunning for maximum downforce, the Chevy is gunning for minimal drag. While the Chevy's have traditionally made better use of their power, that power is only as affective is the aero kits ability to keep the rubber planted. Recall the Chevy's raised front winglet and the crucial role it serves in cutting down on turbulence. Again going back to an excellent observation from Slipstream, if a Chevy ends up in the bumper of another car, damage to the front could spell disaster.

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Likewise, with the Honda designed to remain planted, consider the immense turbulence that it will leave in it's wake. Could it be more than Chevy can contend with and still extract meaningful speed from it's kit?

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Or has Chevy sorted out issues that Honda has yet to conceive? With Chip Ganassi Racing's access to a "secret underground tunnel", it's possible that the Chevy kits have an ace up their sleeve in the form of real world speed and real air over the body. It is not entirely clear from the IndyCar rules whether this kind of testing would be banned before open track testing. It's all speculation at this point.

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That's a lot of speculation. Is anything clear from all of this?

Well, we know that what we're seeing in the renders is not the final word. The kits may be added to or subtracted from as teams see fit. We know from Ryan Hunter-Reay that the lack of power steering may be a big issue, particularly in the Honda camp. And we know that it will be a long-(ish) road ahead to figuring out exactly what works where. The ability for teams and drivers to react quickly to the kits, and make the right changes may determine the whole season. Or it may not.

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Slipstream predicts that Chevy will win at most street courses while Honda will dominate at road courses, Barber and Mid-Ohio to be exact. There could be a number of track records that may be in their final days, as well. But you're going to have to listen to Slipstream for that. (Seriously, GO LISTEN TO SLIPSTREAM!)

Most of all, it's clear that we don't have the numbers yet. What we do have is frilly plumage and bumps and bulges that may add up to the IndyCar version of a flightless peacock. Or it may end up being the most exciting new chapter in IndyCar than we've seen in quite some time. It's doubtful though, whether it attracts new spectators or not, that the racing will be a dud.

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Oh, and it's CERTAIN that these cars look amazing! (Shut up, yes they do!)

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Scott Dixon's CGRT Target Chevy

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Ryan Hunter-Reay's DHL Honda

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Rear end of the DHL Honda

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The Honda in all black looks evil!

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Close up of the DHL Honda front wing, and other front wing, and other front wing, and....

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That's more like it.

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