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BROOKLYN, Mich. — NASCAR officials and Sprint Cup Series drivers will go racing off into the unknown Sunday here at Michigan International Speedway (1 p.m. ET, FS1, MRN, SiriusXM NASCAR Radio), equipped with an adjusted aerodynamic rules package and a lot of questions.

Few were answered on Friday, the first day teams rolled onto the 2-mile track with a package featuring a smaller rear spoiler as well as changes to the front splitter. Single-car runs dominated the lone practice session, no different than qualifying, which ended the first day’s action.

Instances of cars running side-by-side and/or nose to tail weren’t rare. They were non-existent. With two practices on tap for Saturday, some brave souls may yet emerge.

Speed was the topic of conversation on Friday as teams adapted to the changes.

“I am really excited about the fact that not only is it really cool to go 220 mph at the end of the straightaway, but then we have to slow down to 180 mph in the corner,” Aric Almirola, driver of the No. 43 Ford for Richard Petty Motorsports, said. “For a race car driver, 220 mph is fast and it is fun and honestly not that scary because you have to let off the gas to go in the corner.

“What is scary is running 200 mph at the end of the straightaway and 198 at the end of the corner and it really hurts when the right front tire blows out and you hit the wall.”

The discrepancy in straightaway speed vs. cornering speed is expected to open up passing zones. It creates “opportunity,” Almirola said.

“You can drive in the corner a little deeper,” he said. “You can lift a little sooner. It really opens up the driver’s tool box if you will.”

“It’s a nice change of pace,” said Brad Keselowski, a Michigan native who is winless in 13 career starts at the speedway. “We are all kind of learning together how that will affect the racing. I don’t think anyone will have an answer until they drop the green on Sunday.

“That seems to normally be the case here where races are different than practice and qualifying. … It is fun to drive. You enter the corner almost 220 mph and you turn left and the front goes and the back doesn’t always go with it. That is quite a feeling for sure. It is a unique challenge that I think will bring out some of the best racing we have seen in quite some time.”

NASCAR began tweaking this year’s lower downforce aerodynamic package at Kansas, requiring teams to weld rear trailing arms and brackets to limit offset and movement in the rear of the vehicles, decreasing sideforce.

Further changes were put into play for this year’s non-points Sprint All-Star Race at Charlotte Motor Speedway. The number of fans used for cooling purposes, which teams had begun using to move air from underneath the car and create downforce, was decreased and the rear toe alignment was reset in a move to limit sideforce.

The fan and trailing arm changes will remain in place but the rear toe alignment was only for the non-points event.

The latest moves, for this weekend’s race Michigan as well as next month’s event at Kentucky Speedway (July 9 at 7:30 p.m. ET, NBCSN, PRN, SiriusXM NASCAR Radio), consist of the spoiler, deck fin and front splitter changes in addition to those previously announced.

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Two years ago, NASCAR Sprint Cup Series cars created approximately 3,000 pounds of downforce. Rule changes for ’15 reduced that to 2,700 pounds, according to Gene Stefanyshyn, NASCAR Senior Vice President, Innovation & Racing Development, said Friday.

“They’re running the ’16 rules package at 2,000 (pounds), and the package we’re running here in Michigan will be 1,500,” Stefanyshyn said of the downforce numbers. “So it’s been a journey over three or four years.”

Those changes have also reduced sideforce by approximately 110 pounds, he said.

“Obviously we take the aerodynamic forces off the car, it makes the car a bit more difficult to drive for the drivers, but in taking those aerodynamic devices off, we do clean up the amount of air or turbulence around the cars so the cars should be able to move around each other better and pass. So that’s kind of the theory.”

Combined with a Goodyear tire matched more closely to the lower downforce package, the changes have resulted in closer competition on the track this season.

Friday’s activities were more about getting acquainted with the new package; how it will impact competition when cars are three- and four-wide, several rows deep, has yet to be answered.

“I think it’s difficult to visually see the difference, but when you look at the data from the cars, the speed trace is significantly different, the mid‑corner speeds are down a lot, the entry speeds are up a little,” Scott Miller, NASCAR’s Senior Vice President of Competition, said.

“And from some of the driver comments, having to use the brakes pretty hard and maybe even thinking about needing brake cooling and everything at a big track like this is a departure from where we’ve been before, and we’re really hoping that those things actually produce a really, really good race on Sunday.”