I recommend making the camera a fixed camera. So it will not sway around when you turn or crash, it makes it kinda hard to see. Also the Z key is a glitch factory on my computer. It makes all the cars move to the exact same spot, therefor causing a ton of lag. I sometimes need to force quit the game to get it to stop. You might also want to increase the visibility, things are a bit blurry when they are far away.
Other than those things it is a pretty awesome game! The physics are amazing and the crashes are great! Hope to see future updates! (New maps and cars would be really awesome!) :)