Ridge Racer
48 Achievements
3-5h
Speed Demon
You reached the maximum speed with a maxed-up machine, and added a maximum nitrous.
7.1%
How to unlock the Speed Demon achievement in Ridge Racer - Definitive Guide
Note: You must be Level 7 to have the maxed-up machine upgrade. You also need Hi-Nitrous. It doesn't matter what the other upgrades are.
What you want to do is load up any track with a long straight (Highland Cliffs will do). Make sure you have Hi-Nitrous equipped and the auto or ultimate charge nitrous. You want to wait until all three tanks are full before reaching the long straight. As soon as you reach it, press L and R together to unleash all three at once (It's and if you have the other settings). You should reach around 280mph, which is the speed that I reached. Try this on each lap and then if you reached top speed, you will unlock the trophy when returning to the Main Menu.