Driving in the SoBe Beverage-sponsored RX-8 with the "Grey’s Anatomy" star will be teammates Joe Foster and Charles Espenlaub, Mazda said a statement.
They will be competing in the Grand-American GT class of the Sunchaser 1000K.
Dempsey is also expected to drive solo in the 45-minute Mazda MX-5 Cup sprint race at Miller Motorsports Park on Sept. 15.
Muniz has put his acting on hold to pursue a racing career full-time, Mazda said.
Rosie O'Donnell unveils nearly 50-pound weight loss
Putin thinks Obama would save him if he were drowning