Aerodynamics – Syndication Server

2024 Indy 500 aero adjustments

The IndyCar Series has made a few changes to the aerodynamic specification of its cars and a couple of mechanical updates for the 108th running of the Indianapolis 500. The largest involves an increase in potential downforce with the rear wing. …

The IndyCar Series has made a few changes to the aerodynamic specification of its cars and a couple of mechanical updates for the 108th running of the Indianapolis 500.

The largest involves an increase in potential downforce with the rear wing. Teams were restricted to a maximum nose-down angle of five degrees at the 2023 race and have been given an additional four degrees of inclination to use with the new 2024 limit of nine degrees.

Teams are allowed to continue using three Gurney flaps of varying widths atop the rear wing, with 13.2 inches, 24.5 inches, and a full-span Gurney at their disposal; all are 3/8th of an inch tall. With the former limit of five degrees, teams made use of the wider Gurneys to produce more downforce, but it came with a noticeable reduction in top speed. By allowing a greater wing angle range of up to nine degrees, a better compromise of downforce and top speed is made possible.

[lawrence-auto-related count=3 category=1408]

“A lot of teams will put the small Gurney on first because it’s a small and pretty efficient piece,” Arrow McLaren technical director Nick Snyder told RACER. “But as you go to bigger Gurneys, it gets less and less efficient, so there’s a trade-off in there somewhere. And each team is going to have their own wind tunnel data of when they start adding more angle or when they put the bigger Gurney on.

“If it’s a cool race, then you probably won’t see anybody putting a Gurney up there because you’re gonna have nice dense air. But if it’s a hot, sticky race day and track temps are 120 degrees, you’re gonna see guys pile on the downforce; probably a mix of who does a big Gurney versus who does more wing angle.”

The series has also removed the option of using the trimmed sidewalls at the exit of the diffusers — next to the inside of the rear tires–to reduce rear downforce and drag; full-length sidewalls are required. IndyCar has also deleted the use of Gurneys from the trailing edge of the underwing flaps.

Up front, the use of two miniature barge boards at the leading edge of the underwing has been altered; the inner barge boards are now unapproved, leaving race engineers the single outer barge board to install on the left and right side of the underwing to add downforce.

All of the newly prohibited items were rarely used, and as Snyder sees it, the changes were done to help IndyCar teams save money within their Speedway development budgets.

“I think that was a lot of the motivation,” he said. “As soon as you change anything around the floor of the car, you have to go map the car, you have to run through an entire right height map. Whether you are doing it in a wind tunnel, doing it with CFD (computational fluid dynamic software) or doing a straight-line test, every aero combination just adds a ton of runs you have to do they get the data.

“So if there’s parts nobody’s running and IndyCar takes those parts and makes them not permitted anymore, it actually saves us money by reducing the amount of testing and the amount of resources we have to put into it. The trimmed sidewalls was a desperation piece almost nobody really ran last year. I think a couple of cars dabbled with those inner barge boards, but nobody is embracing those. So they just took away pieces that nobody was using.”

On the mechanical side, stronger new rear suspension uprights were introduced at the rain-shortened Indy Open Test in April and are installed on every car in response to the rear upright failure that occurred last May when Kyle Kirkwood’s car was hit by the crashing car of Felix Rosenqvist. Stronger retaining rings for the wheel bearings are part of the upright revisions as well.

The new rear uprights also feature a change in how the rear tethers, which are designed to keep broken suspension attached to the chassis, are affixed. Previously, the tethers were mounted to the studs that hold the rear brake calipers in place, but with Dallara’s upright redesign, the tethers bolt directly to the rear uprights.

A number of changes to the Speedway rear wing mounting system complete the alterations for 2024; all have been done to improve energy absorption and distribution in a rearward impact.

A new front mounting clevis has been designed to spread impact loads more evenly through the attenuator, and at the rear, new bolts/studs for the wing mount have been installed that have a lower threshold to break before the wing and attenuator compress as a unit. Finally, the x-brace used to strengthen the Speedway wing mounting and adjusting system has been removed.

The combination of changes being done reduce the amount of damage the wing mounting system does to the attenuator on its own in a crash, and thereby allow the attenuator to better perform its job in isolation.

A wide range of Indy 500 aero options for teams to ponder

If the 107th Indianapolis 500 is run in similar ambient conditions to last year’s race, NTT IndyCar Series teams will have the ability to apply approximately 250 additional pounds of downforce to their cars if all the new and existing aerodynamic options are installed for the May 28 contest. All of the items will make their debut at this week’s Thursday-Friday Indy Open Test.

The biggest year-to-year change is found at the rear of the Dallara DW12s, which wear the sleek UAK18 bodywork that was introduced in 2018. Two downforce-adding items have been produced by Dallara, starting with new rear wing pillars which enable a valuable increase in wing angle range. The idea was originally suggested to the series by Arrow McLaren driver Alexander Rossi.

Previously limited to a maximum of two degrees of positive inclination, the new rear wing pillars make it possible to crank up to nine degrees of downforce-increasing angle into the rear wing, but for this year’s event, the series is limiting a maximum of five degrees.

Attached to the rear attenuator with a sliding mounting mechanism, the pillars (in blue) can be quickly adjusted during a pit stop with a socket on a speed-handle to increase or decrease the rear wing angle to suit the driver’s needs.

The move to the new pillars and a higher ceiling for rear wing downforce will be useful in Indy 500 practice sessions when drivers run in packs and work with their teams to refine the car’s aerodynamic balance in turbulent air, and on race day. No changes have been made to limit going in the opposite direction on wing angle for qualifying, where teams run at negative numbers — nose up — to shed downforce for the four-lap blasts.

According to A.J. Foyt Racing technical director Michael Cannon, who earned the last two Indy 500 pole positions at Chip Ganassi Racing with Scott Dixon, the new pillars will have a surprisingly large impact on the race.

“In the past, you were allowed a maximum of plus-two degrees and after that, you start putting Gurneys on to make more downforce because you were limited on wing angle and the Gurneys were a workaround to get more, but it didn’t help the cars behind,” Cannon told RACER. “So with what they’ve done here in giving us up to plus-five, we have more steps of downforce we can go, and each degree is a nice little increment.”

By giving teams three extra degrees of rear downforce to use, the reliance on wide Gurney flaps should subside, and as a result, turbulence should be reduced, which could inspire more passing attempts.

“Ever since we’ve had the aeroscreen, if you’re the leader, life’s not so bad,” Cannon said. “If you’re second, you’re starting to get some turbulent grief. And when you’re the fifth car in line, you’re losing over 20 percent of your downforce. So that’s why you’ve seen people [when the maximum was plus-two degrees] rock up during the race with full-span Gurneys on the rear wing and they’re competitive because they’re living back in misery-ville. They’re in the big vacuum.

“The guys that have the big rear wing Gurneys on have that much more grip, and when the guy in front of them that’s on a little bit less downforce has to lift, the big Gurney guy just leaves his foot in it and gets past him.

“It’s not the race-winning downforce with the big Gurney, but it’s good survival downforce. What they’ve come up with is the ability to take it to a higher angle and have more downforce while also keeping the efficiency of the car decent and reduce some of the turbulence. And it’s the turbulence coming off the cars that’s bouncing you around and making the car nervous because if you’re running behind somebody that’s got a full-span Gurney, there’s a lot of tumbling air behind there and it’s pretty messy to sit behind. So, giving us some extra range to make more downforce with the wing should help everyone to go away from those full-span Gurneys.”

The other new allowance for the Speedway is the optional use of one-inch Gurney flaps at the trailing edge of the diffusers (in blue), which is a carryover from IndyCar’s road and street course rules. Use of these Gurneys are a nice way to add downforce through the car’s underwing, and since these tall flaps aren’t sitting up high in the airstream like a Gurney affixed to a rear wing, they do not create an excessive amount of turbulence.

With the new five-degree rear wing angle maximum and the optional diffuser-exit Gurneys, teams have newfound abilities to dial up downforce in race-day configuration, but since drivers need their cars to be balanced front-to-rear in order to have confidence in its handling, teams will need to add matching levels of downforce to the front of the cars.

Race engineers will use the familiar front wing adjusters to apply more downforce, and have a new option to install a second barge board (in red) which debuted at Texas Motor Speedway and mounts to the inside of the other optional barge board, which was used last year. Each barge board increases downforce, but also increases front ride height sensitivity, so it will be interesting to see if teams opt to run with the single barge board on both sides of the car, or try double barge boards and trade the downforce gains for imperfect handling.

“If you’ve got a bunch of rear wing angle on the car, you’ve got to find a way to get balanced at the front,” Cannon noted. “So it’s great that we can have more rear wing, but you might have to do some things to balance it at the front that aren’t great, so I don’t think everybody’s going to pile on everything they can get, but it all depends on the weather because you never know what you’re going to get. But it’s nice to have a range of downforce options, even if we don’t use all of it.”

Finally, teams have the optional Gurney to install on the wing-shape infill at the outer portions of the front floor section, and in a mandatory addition for every team, stability Gurneys (in green) make their debut along the top outer edges of the sidepods and rear tire ramps.

The series will also introduce a new and taller cockpit head surround at the Open Test. The revised design was done to prevent a driver’s helmet from scaling over the back of the longstanding design in a rearward impact.

Production is ongoing, with a plan to have one for every entry as the month of May begins, so for the test, IndyCar will distribute 18 of the new safety devices (in blue) — ensuring every team has at least one — with the hope for multi-car teams to ensure each driver samples it at speed before they become mandatory for the start of official practice in just under a month.

IndyCar tech download: 2023 Texas aero

Aerodynamics will play an increasingly important role during this weekend’s NTT IndyCar Series race at Texas Motor Speedway. New allowances for the fast 1.5-mile oval will give the 28 drivers on the entry list and their race engineers the potential …

Aerodynamics will play an increasingly important role during this weekend’s NTT IndyCar Series race at Texas Motor Speedway.

New allowances for the fast 1.5-mile oval will give the 28 drivers on the entry list and their race engineers the potential of adding up to 10 percent more downforce than last year’s aero specification could produce, which equates to approximately 250 pounds of downforce.

At the front of the Dallara DW12’s floor, the Italian firm has produced a second optional barge board (above, in red) that adds downforce. With the increase in downforce, an increase in front ride height sensitivity also comes as part of the puzzle to solve.

On the outer flanks of the floor’s forward section, the infill Gurney flap (below, in blue) has been changed from mandatory to optional.

And at the back of the cars, the outermost portions of the diffusers have gone from an optional trimmed sidewall to channel the air leaving the bottom of the cars to optional full-length sidewalls which do a more effective job of concentrating the air and making more downforce.

The new aero options have been put through intensive computational fluid dynamics, simulation, and driver-in-the-loop testing prior to Saturday morning’s lone practice session, so most teams will have an idea on what they’ll want to try for qualifying and race setups.

But with the short 50-minute session serving as the only on-track outing for the series prior to qualifying, teams will likely be rushing to give the barge boards and Gurneys and sidewalls a try along with all of the other to-do items on their run plans.

“Texas is actually pretty interesting because of the new aero bits we get to play with,” Scott McLaughlin’s Team Penske race engineer Ben Bretzman told RACER. “What’s interesting is there’s not much running. It’s really limited and it’s gonna push everybody pretty hard on Saturday, because obviously we start running so early and you have to decide if you want to do qualifying work, race work, or both.

“The sidewall bits bring a pretty substantial chunk of downforce which also changes the ride profile on the car. So the teams have to figure out where do they want to run the cars and where do you want to take advantage of those sidewalls. Texas is different than any other oval track from the standpoint of that type of underwing configuring the right height profile of the car. We’ll see what people do with the little Gurneys; there’s a downforce gain there but will people take those off?”

Factor in the time required to get a handle on the correct pressures for Firestone’s tires along with refining camber settings, damper settings, damper builds, springs and the rest of each car’s mechanical setup, and the new aero options are part of a bigger menu of to-do items to cover from 8:10-9am Saturday morning in Texas. Qualifying for the 250-lap race starts soon after at 11:15am.

“And the new inner bargeboards are one step more you can go than just the single ones we had last year,” Bretzman noted. “The cars were really sensitive to one, so two will make it even more sensitive. With all of the steep banking that Texas has and the speeds we go and the compression we deal with in the corners, ride heights are really important to get right.

“So like with the full sidewalls at the back (above, in blue), we have to be careful to hit the optimal ride height at the front of the car with the barge boards in mind because their full effectiveness is affected by right height as well. Nailing both ends is critical, so there’s a lot for us to sort out in less than an hour of running.”