I tried the latest version (0.5.1), but in my Opinion it's barely playable, the car is just out of control.
However, this is certainly just a bad choice of your ODE Parameters, try to fix this for the next release, I might even help you out with this, because I created an ODE-based Car-Driving demo recently, that does fairly well in this respect I think.
BTW. I like your Project being that active, Keep it on.
PS.: Any Chance that it'd be possible to switch to the Irrlicht Engine for 3D? (http://irrlicht.sourceforge.net/)
This might make it easier to concentrate on gameplay and features.
I agree, the physics still needs a lot of improvements. I think that the current problem is in my (self-made) collision detection code, but if you've experience with making ODE simulations, then I'm sure that you can help.