BROOKLYN, Mich. — In an incessant quest to enhance passing at superspeedways, NASCAR tried divergent directions — from underpowered cars with high grip to ill-handling models — during a Monday test at Michigan International Speedway.

The nine-hour session, which included 10 Sprint Cup teams running several simulated races on the 2-mile oval, was critical to set the framework for next season’s rules. NASCAR vice president of innovation Gene Stefanyshyn, who oversaw the test, said teams want the regulations for 2015 cars finalized by early September.

As NASCAR weighs whether to detune its engines, add aerodynamic deflection devices or even allow drivers to make significant suspension adjustments from the cockpit, the ultimate goal is a combination that increases the likelihood of better action — particularly on the 1.5- to 2-mile tracks that account for 14 of 36 races on the Cup circuit.

“We’re looking for a fan-centric direction,” Stefanyshyn said Monday. “Fans have said they like a lot of passing, a lot of side by side racing, a lot of lead changes. That’s what we’re endeavoring to do.”

NASCAR has focused much of its attention on the aerodynamic effects on the front of the car, trying to lessen the impact of turbulent air on a trailing car (which upsets the handling of drivers trying to keep pace with or pass the leading car).

For part of the Michigan test, cars were outfitted with “dive planes,” tiny fins attached to the sides of the front bumpers that improve downforce (which helps keep a car glued to the track). Dive planes are found in many forms of auto racing, such as sports cars and rally cars.

“It’s a tool so the trailing driver will feel the car is more predictable,” Stefanyshyn said. “So the driver doesn’t lift off the throttle and that way can stay closer (to the lead car).”

Essentially, the objective is ensuring the leader has less of an advantage at aerodynamically dependent, high-speed tracks such as Michigan, where Jeff Gordon set a qualifying record at 206.558 mph last Friday. At high speeds, aerodynamically sensitive cars tend to spread into single-file lines because passing becomes difficult in turbulent conditions.

But fixing that also is a tricky proposition, given the plethora of available options and lack of definitive criteria for determining the best solution.

“I don’t know what defines if it’s working, necessarily,” Joe Gibbs Racing’s Matt Kenseth told USA TODAY Sports during the test. “But I think it’s a good exercise to run lots of stuff and see if they can find something that they like how it looks better.

“Racing from the start of time has been the fastest car is going to drive away anyway. You never want to make it where the fastest car can’t win. I don’t think a car that’s slower should be able to pass a car that’s faster and win a race.”

NASCAR also tested decreasing speeds through three horsepower configurations — 850, 800, 750 — through the use of restrictor plates. Sprint Cup cars roughly have about 900 horsepower. Stefanyshyn said if NASCAR elects to detune the engines, another method would be used.

The final configuration at Michigan restored horsepower but lessened downforce by 30%. Stefanyshyn said many drivers have advocated that approach because it reduces the importance of aerodynamics and puts more of an emphasis on the driver.

“I’ve always been a fan of less downforce and more horsepower,” Kenseth said. “I think the more time you’re off the throttle in the corner, and the more you have to drive the car and the more you can have a setup that saves the tires in the short run. For the fan part of me, that creates better racing because you can pass better in the corners.

“But this year they put a ton more downforce and drag on the cars, and I guess generally people thought the races were better. It’s always going to be hard to pass when you put the fastest car in the front. I don’t have a problem with that. I want to see the best car win.”

Danica Patrick, who also participated in the test, said it was important to avoid making too many tracks akin to the restrictor-plate racing. At Daytona International Speedway and Talladega Superspeedway, plates restrict airflow to the engine and greatly reduce horsepower, which keeps cars bunched into tight packs while running at full throttle.

“That’s easy to drive, but I don’t think it’s fair to have all the racing like that,” she said. “It’s entertaining, but you need tracks that are dedicated to getting the car really fast. Tracks where you slide around a lot, it makes for passing, too. I think we need to figure out how to make the cars transition from the beginning to the end of a run. That creates passing.”

Despite a few setbacks in the morning (a second simulated race was canceled after an engine failure for Kenseth), Stefanyshyn said this was the only test planned before next year’s rules are confirmed. NASCAR is planning to re-evaluate the efficacy of the new rules after the first six races on 1.5-mile tracks next year.

NASCAR also tested a cockpit-controlled panhard bar that would allow drivers to alter handling (which is more common in IndyCar-style racing). That adjustment currently is made by crew members with a wrench during pit stops.

“We’ve been hesitant to throw all kinds of adjustability on the cars because we like a pure historic form of racing,” Stefanyshyn said. “We’ll investigate whether giving that control to the driver is better rather than wait for a pit stop. By putting this in their hands, we can help them correct it on the fly.”

Kenseth said he wasn’t sure if in-car adjustments would help enhance passing.

“I haven’t put a lot of thought into that,” he said. “As a driver, sometimes it’s fun to have more toys to play with, but the crew chief would probably rather not have that.”

Other competition-related changes that NASCAR is working on for 2015:

–An online rulebook scheduled to go live in October that will offer teams access to computer animated drawings and 3-D illustrations.

–Officials equipped with Surface tablets at the track to help streamline inspections.

–A new video analytics system for officiating the pits will be tested during the Chase for the Sprint Cup (running in parallel to the current system that relies mostly on officials). The 2015 system will rely on enhanced cameras and software that will be analyzed by eight officials in a high-tech trailer.