After meeting up with Chan he says he can't win without your help. You have to knock the racers of the track during the race. Get a fast car (for example the Comet next to Chan's garage) and head for the starting grid. When you get there you'll see the champ crashing his car and dies. Now only Chan and 3 rivals are left in the race. Crash into the cars to ram them off the track until Chan takes the lead. You'll need to maintain Chan's lead until the end of the race (3 laps). After you're done go and congratulate Chan with his victory. He'll say that he didn't need your help after all.