I have little knowledge about the blender game engine, as far as I know it has a physics module built in, however that might not be the PhysX Engine I now know thanks to Unity.
However, some basics will still apply.
1) You need to be aware, whatever you setup in the physics engine is a pure game logic representation / abstraction of your 3D Model (which in turn is kind of an abstraction of a real world object).
This is important to note. Attaching the Physics model to your game object mightnot move the 3D Model in any way ... this depends a lot on how the physics component works and the 3D Model parenting is done.
2) for example, If you want your 3D Model wheels to move with the Physics Wheels (Wheelcolliders in PhysX), you need to write "glue code" that gets the Physics Wheel position / rotation, and then applies that to your 3D Model.
This is at least true for the PhysX Wheel colliders.
2b) There might be some physics modules for your physics engine that already do part of this "glueing together" out of the box. In PhysX, for example, there are "joints". these will combine 2 colliders with a joint. As long as your colliders parent object contains the right 3D Model, the joint will affect the 3D Models without "glue code".
3) For the driver, the simple physics stuff will not suffice anymore. If you want to go cheap, and are happy with a slightly odd (dead ) looking driver, you could try softbody or ragdoll physics.
If you want to go the full distance, and want a realistic look, you need to do real animation on your driver 3D Model. That is a whole new topic altogether.
For the simple vehicle physics (minus the driver), you will most probably find good tutorials on the web. For Unity there is about half a dozen really good car racing tutorials that explain this setup, and there is at least one discussion where the pecularities of a two wheeled setup (which needs some additional code in addition to the standart wheel physics to keep the vehicle upright) were discussed in detail.
I can't really help you on the Blender Engine, sadly. But I guess, given the size of its community, some tutorials must be around.
Last thing to note, be aware that anything besides the most basic unrealistic car racing will need some HEAVY scripting layer on top of the physics engine to get any realistic result out of the physics engine.
Just be warned: No physics engine will do 100% of the work for you. What you see in all the good racing games with physics out there is more hard work of programmers and designers than Havoc or PhysX at work.
Edited by Gian-Reto, 28 July 2014 - 09:45 AM.