This cheat involves getting a gold medal on the B-5 license test. I've heard that it is nearly impossible to get a gold on this test, so i found this online. First, you must turn the traction control off. Then, as soon as you start driving, keep your steering hard to the right and keep on the throttle. There is a lane of asphalt that leads to the sidewall on the right of track. Hit the wall as hard as you can in this area. I think that this only works if you have enough speed to make the rear of the car jump. Anyway, my record for this license test is 3.078 seconds, 19 seconds being the gold time
. There's a video on youtube titled "Gran Turismo 5 GT5 Funny Fail License Test" which shows this cheat in action in case you don't understand. Enjoy!