You can win races and events using a less powerful vehicle against better competitors by using the Nitro appropriately. Draft, drift, perform jumps, go though Nitro Boost (the blue arrows), and attempt near misses to increase your Nitro. Performing those actions also increase the amount of money awarded after the race is completed. You can use Nitro at any point in the race. Do this as often as possible, as soon as it is ready. The best method to fill it is to drift, however be careful when doing this on sandy track surfaces.