Here's how it went down -- Keselowski tried to make a move to pass Joey Logano to get into first place. Instead, he clipped the back of his teammate’s car ... resulting in a 17-car wreck that caused several drivers to fall out of the race in the process.

Cameras caught Keselowski after the crash ... and the dude was straight-up PISSED -- he walks away disgusted from his wrecked #2 Ford, then takes off his helmet and smashes it to the ground with smoke coming out of his car.

Keselowski spoke out about the unfortunate ending on Twitter ... calling it a "heartbreaker."

"My body is fine but my heart is broke," Keselowski said. "Months of studying, months of tremendous car prep from the #2crew & in the perfect position at the end..."

"Yet, Another #DAYTONA500 slips away..."

Keselowski told reporters after the race he didn't regret the move and was just trying to win. "Don’t feel like I made a mistake, but I can’t drive everyone else’s car. Frustrating."

The wreck is especially sad for Keselowski, since he had the chance to become the second active driver to win NASCAR’s sacred unofficial grand slam ... having won the Southern 500, the Brickyard 400 and the Coca-Cola 600.

Once the crash was cleaned up, underdog Michael McDowell went on to cross the checkered flag for his very first NASCAR win. He was previously 0 for 357 until Sunday!!

Shoutout to Michael McDowell for sticking to and getting his first win ... and hopefully Keselowski and his car can sort it all out in couples therapy.