Use your nitrous oxide injector (ctrl key) for a speed boost. The indicator on the right near the speedometer shows how much you have left. I'd only use it when you are entering a straightaway and are lined up ok at first or you won't be able to control it.
The are a couple U-turns in the forest track where you have to slow down a lot or you will crash every time. They are the first 2 turns you come to after the long straightaways. I just let go of the gas pedal completely quite a ways before I get to them and don't hit it again until I'm more than halfway through the turn and I'm headed the other way.
I'm not the greatest driver but I can beat the street track almost every time and beat the forest track pretty often now.
If you still have a hard time, there is a shortcut on hte last turn before the end of the lap right before you go back on the street. There is a pile of logs that angle up to the side of a truck. Go straight at the logs and up them to jump over the truck and you won't have to make part of the last turn.
This comment was edited on Nov 5, 00:24.