Gee I hope I read the post right.
Anyway: Here are some fairly challenging races.
3 laps at Tsukuba
Nissan Race
1:Nissan Cube
2:Nissan Elegrand
3:Nissan Stagea
4:Nissan Fairlady Z Version S (Z33)
5:Nissan Skyline GT-R V-SpecII Nur (R32)
6:Nissan R390 GT1 (Race Car)
(*Give them a 37.5 second head start)
(**Add 12.5 seconds for every extra lap the race is)
Mazda Race
1:Mazda Cosmo Sport
2:Mazda Roadster RS-II (NB8C)
3:Mazda SAVANNA RX-7 GT-X (SA22C)
4:Mazda RX8 Type S
5:Mazda RX7 SPIRIT R (FD3S)
6:Mazda 787B (Race Car)
(*Give a 40.5 second head start)
(**Add 13.5 seconds for every extra lap the race is)
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All you really need for these fun races is a brand with R, A, B, C, D, and E class cars. You can then improvise (ex. Replace Nissan Cube with Nissan Moco etc.)
The fun part of these is you never know if you'll win because all the cars are seperated. Plus, your are passing someone on almost every lap.
Edit: You don't neccisarily need all the same brand, you can use the same country, or even just the same color etc. But it's usually more fun if they have something in common.
Edit 2: Hmmm, seems I may have made a mistake. Is this going to be a competition? Because it would be hard (impossible) to get the head start perfect. If it is a competition I will rethink it and come up with something else.