Joy Ride Turbo

To unlock this achievement, you have to finish in the top three of the 3 sets of races in the 300 HP category (White Knuckle Nightmare, Wrecking Ball Showdown & Technical Summit) to unlock the final set, 300 HP Grand Prix. You also have to place in the top 3 for this final set of races for the achievement to unlock.

You will need to use the most expensive car of the corresponding category, so you should go for this achievement after getting the car parts you need to be able to buy those cars. Also, some of these tracks are hard, and the AI seems to be super-human sometimes, so if you're having trouble with getting 3rd or better in the general position, go to time trial and learn the track, look for the shortcuts and detours that work best for you using the same car that you will be using when racing.

For me, the most difficult set was the second one because I'm useless in the third track of that set, so I needed to place either first or second in the first two races. Fortunately, in the first one you can skip a long curve by just smashing some fences and going in a straight line just before the finish line, and in the second one there is a great detour through a tunnel to the right very close to the starting point. You can go at top speed without bumping into obstacles and there's almost no cars there.

Finally, for the 300 HP Grand Prix (the final set) you can pick any car category, so be wise about it. If you are like me, i.e., not a very good driver, you might want to sacrifice speed for stability, which is what I did & ended up first for the event (I picked the most expensive truck model, the yellow one to the right)