In 1985, DiGard had Bobby Allison battling for the championship. For the Firecracker 400 at Daytona, DiGard set up and raced what is called a Research & Development car (a one-off car entered to a race primarily for team improvement) with Greg Sacks at the helm.
Instead of simply collecting data for the team, Sacks won the race.
However, it has been alleged -- reportedly admitted by DiGard crew chief Gary Nelson -- that the car sneaked through inspection with an oversize engine, and thus the team cheated.
The impact of the R&D car was significant: Reportedly angered that the team was focusing its attention elsewhere, Bobby Allison left the team mid-season -- two weeks after Sacks' July 4 win. Sacks was hired to race for the rest of the year, but never captured another Top-5 finish in 1985.
Richard Childress Racing has entered an R&D car sporadically since 1988 and up until the mid 1990s.
In 1994, an RCR car intended as an "R&D car" was entered into the last race of the season, and promptly dropped out of the race immediately after the first laps. It was extra security for Dale Earnhardt to win the championship: he needed to finish above 31st spot to mathematically win. The R&D car dropped out and took 31st, securing Dale the championship in case his car had any failures.
They do development work on the car in testing sessions throughout the season, and also travel to the Grand Prix in case the racing drivers are injured.
Test drivers sometimes get promoted to full-time drives. Sebastian Vettel, who substituted for BMW race driver Robert Kubica in 2007, was hired as a full-time race driver with another team later in the season.