Yea, so if you start at 6am (custom track) and you want to go to 8pm - thats 14 hours of "game time"- and from what I got from the OP, you want to do 2 hours (120 min) of real time during the race?
So, go to the Ring (in a car with a clock) or another track where you can control the start time and the "x1, x2, x3" settings and then play with them until you find one where 1 "game hour" equals 8.5 minutes of "real time".
With an 8.5 min "game hour" you will go 14 hours (day to night) on your custom track in 119 min (the 2 hour race).