Updated

NASCAR took the final step toward setting its 2014 rules package with a critical test session Wednesday at Charlotte Motor Speedway.

The test featured four simulated races with four different configurations on the Gen-6 Sprint Cup Series car. Drivers had to attend a mandatory debrief with NASCAR following each session to give feedback on the aerodynamic, engine and suspension combinations.

NASCAR had 30 cars participating in the test, and planned to choose the configuration most favorable among drivers to test with a tapered spacer designed to reduce engine horsepower.

The goal of the test is to improve the racing at 1.5-mile superspeedways, which has been a stated goal of NASCAR chairman Brian France. He was scheduled to attend the test Monday, but rain postponed it until Wednesday.