Lost and Found Race (1 lap):
At level 20, RP payout was 1000.
At level 22, RP payout was 1050.
At level 100, RP Payout was 3000.
This leads me to believe that the base RP would be 500, then 25rp for each additional level up to 100. Maybe someone rank 120 or so could see if alters past or equal to 120. I have a feeling this info is probably common knowledge but I haven't read anything here to suggest that, then again I'm kind of new around here...
level 65 = 2125
level 66 = 2150
so yeah pretty spot on
nice find op
The race RPs seem to be scaled to the amount of RP needed to move up one level, so it takes about 9 to 10 solo races to advance one level, high or low. One thing that matters (or used to), however, is that when you are racing solo, don't cross the finish line before 4 minutes of race time. You get more RP after 4 minutes, and you get a little more money after waiting until 6 minutes.
I just multitask doing computer stuff while doing those solo races, so most of the waiting time to reach 4 minutes is not wasted. I did about 80 tedious levels, 800 to 900 solo races, to get to my present level.
Also, you need to cooperate with another player, to trade wins, so you can get your 50 race wins to unlock all car mods. The GTAF Meetup topic is good for arranging that.