Go to the Driving Park Test course (large oval track) and set it up for two or more laps. Use your highest top speed scar and have a second player choose a slow car. Set the race to AI for both players and continue. Eventually you will get the jackpot race multiplier to "6". If it lands on you and you are in first place, you will win all of the player two's money, and it will add into yours then multiply by six.