136 races x however many minutes it takes to do 1 race = approximate answer.
So Since My First post at 4:35 i have completed 51 Races In 2 Hours and 7 minutes
Track layout doesn't matter since it's Bspec. It's just a matter of using the race that takes the least amount of time to finish.It's not an issue anymore, but I'm thinking that something like the Supercar Festival at Daytona Superspeedway would be the easiest grind. High speed and not so many turns.