NASCAR competition officials have scheduled a two-day test this week at Phoenix Raceway to evaluate potential updates to the Next Gen car’s rules package, including possible aerodynamic alterations, trial runs using mufflers for select races, and efforts to curb rubber buildup in wheel wells.

Six Cup Series teams are scheduled to participate in the testing sessions Tuesday and Wednesday at the Arizona oval. Officials plan to divide the test days into five sections – an initial practice run with the current rules configuration to establish a baseline, and then four additional sessions with different combinations. The changes are intended to improve the quality of racing on road courses and oval tracks measuring 1 mile in length or shorter, but officials indicated that any benefits found on those courses should carry over to all track types.

Teams, drivers and officials will aim to assess any aerodynamic improvements in traffic and passing ability through changes in the car’s floor, or underwing. The updated underside uses some facets that have been developed in the Garage 56 Le Mans project’s test car, reshaping the area behind the engine panel and extending the diffuser strakes downward but leaving the current splitter in place.

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Dr. Eric Jacuzzi, NASCAR Vice President of Vehicle Performance, says that computer modeling of those changes created more downforce overall, but that those demonstrations also showed a radical difference in traffic behavior. “It doesn’t lose as much front downforce when it’s behind another car, so it doesn’t push as it gets closer,” Jacuzzi said.

To offset the additional downforce, three of the four new trial configurations will evaluate the use of a smaller rear spoiler – reduced from the current 4-inch height to a 2.5-inch size. It’s a potential change that’s supported by anecdotal driver feedback and data analysis; this week’s real-world test at Phoenix should provide another measuring stick.

“You can tie it back to if you watch the cars run on the track, right? You notice they run ‘nose up’ a lot, and it’s because the more air you can put to the diffuser, the more downforce it makes in the back,” Jacuzzi says. “So we made these changes that put more air to it, so that lets us knock the spoiler height down and still be at roughly the same downforce that we were at the start of the year. We assume that teams have gained a little bit, just optimizing where they can build things. So we’re roughly in the same spot that we were at the start of last year, but with a much smaller spoiler.”

The test’s second day will also explore the potential use of exhaust mufflers to reduce engine noise for two unique events set in metropolitan areas – the Feb. 5 Busch Light Clash at the Coliseum in Los Angeles and the inaugural Chicago Street Race in the Windy City’s downtown. Jacuzzi said competition officials do not have a projection in mind for the sound reduction, “other than to not impact the engine such that it needed to be mechanically altered, so any changes they need to make will be electronic — tuning and things like that.”

Jacuzzi says he expects mufflers to create a 6-to-10-decibel decrease, which would be a small but significant number in the car’s sound. But he also was quick to add that officials would take care not to lose the V8 rumble that has been a trademark of the fan experience.

“It’s a little less harsh,” Jacuzzi said. “It’s still going to be loud, and you should still wear ear protection, all those things, but it’s just going to knock some of that edge off. It’s not quite as aggressive, but it’ll sound the same.”

Officials will also work with the teams to address the accumulation of tire rubber underneath the car and in the wheel wells, a buildup that created the potential for fire hazards during the Next Gen car’s first season last year.

“What we’re doing is we have these panels that essentially seal the front splitter to the hood, if you will,” Jacuzzi says, “and we’re hoping that the rubber that normally would get thrown onto the splitter and then sort of make its way under the car will be mitigated. We’re going to run the first day without them, ask the teams not to clean anything up so that we can photograph everything, and we have a lot of pictures throughout the year. But then the second day, we asked them to clean everything out and then install these panels. And at the end of the day, we’ll revisit and see, have we affected this and we’re pretty confident that this will solve a lot of our problems.”

Select teams at the test will also try out potential updates to the car’s steering and braking systems. A larger-bore steering rack will be tested as a possible solution for issues at tracks with higher cornering loads. Teams will also try different brake rotors to improve consistency with wear.

“We’re having some warping issues and things like that, so essentially where one side of the disc is getting cooler than the other side, it causes it to kind of bend over and push the pads away, so that when they press the brake, the brake doesn’t respond, it’s been moved away,” Jacuzzi says. “So the intent is to deal with some of these thermal issues and see if we can get it consistent. It’s not a uniform issue; it kind of depends on what brake pad they’re using and all these things, but we’ll pick some teams who have been vocal with their issues and try to get them to help us address this.”

Officials plan to test each configuration with two types of sessions – a 90-minute open practice followed by a group run of 30 to 40 laps each to simulate race conditions. Drivers, crew chiefs and officials will debrief after each day of testing.

From there, the implementation of any potential changes to the seventh-generation Cup Series stock car could come as early as this season, pending further evaluation and testing.

“I don’t think we would dismiss it,” Jacuzzi says. “I think one of the things we were concerned about is making sure that everybody had the opportunity to evaluate it. So we would probably move forward with some sort of organizational test, TBD on that, and then sort of decide what the rollout plan would be, to be most efficient to the industry and make it fair for everybody. Obviously in the past, we’ve used the All-Star Race (as a testing ground), but that I don’t think fits with what we’re trying to do. The priority would be to make sure we have an org test and get buy-in and then sort of figure out a logical rollout plan from there.”

NASCAR officials’ list of teams expected to participate in the two-day test include:

• No. 1 Trackhouse Racing Chevrolet
• No. 6 RFK Racing Ford
• No. 20 Joe Gibbs Racing Toyota
• No. 22 Team Penske Ford
• No. 43 Legacy Motor Club Chevrolet
• No. 47 JTG-Daugherty Racing Chevrolet

Additionally, the two-day session will include track time as part of a “select driver test” for seven-time Cup Series champion Jimmie Johnson and his Legacy Motor Club group. Johnson has planned a limited Cup Series schedule this season, returning to NASCAR for the first time since the end of his 2020 campaign. Kimi Räikkönen and Mike Rockenfeller had similar test sessions ahead of their Cup debuts last year, using on-track time reserved for elite drivers with no experience driving the Next Gen stock car.

The Phoenix facility, which has hosted NASCAR’s championship weekend the last three seasons, was also the site of a Next Gen organizational test last Jan. 25-26.