I just B speced Sathe Circuit 24H II (the long straight ) in a Nissan R92 (won from 1000 km race) with the Turbo stage 4 added and with super hard rear tires and hard front.
Left settings at default and let B spec go for it.
The AI challange was a Mazda 787 B and Sauber Mercedes.
Finished first by not much more than a minute over the Mazda.
My car would lose 10-15 seconds every 10 laps as it made a turn on the straight where the 2nd chicane is located on Sarthe I.
I was pitting every 7 laps on pace 3, the Sauber pitted every 8 laps, and the Mazda every 9 or 10 laps.
B spec was about 5 seconds per lap faster than the Sauber and Mazda.
B spec points were 7064, with skill at 85 , 69 & 69 at the start.