I think you're underestimating how complex suspension, tire contact, and drivetrain models can be. Multi-link suspension, for example, tilts the wheels as a function of displacement and steering. This tilting will have an impact on tire contact, and cornering force will depend on this as well as the material of the road (dirt or asphalt, for example). When you're trying to model hundreds of cars according to factory specs, as well as under tuning, your model needs to be quite complex to be accurate.
A car's suspension is very easy to model, even if multi-link. For a given steering position, every suspension linkage in the world is a one degree of freedom system. You simply model the lateral displacement, wheel orientation, etc. as a function of vertical displacement. The moment of inertia and mass of all these elements are reduces to one effective mass. There's no need to simulate every element.
Similarly, you don't need to physically simulate every element of the drivetrain as that would be sheer stupidity. You just need a mathematical model from the pedals to wheel torque that uses some internal state variables like current engine RPM, turbo pressure, current wheel velocity, gear, etc.
A "complex model" capable of everything you said doesn't need to be computationally intensive at all. A hundred variable formula for each major part of the car can be handled with ease on a PS1. You just need a bunch of numbers to specify the effect of each vehicle/part/surface, and that's about content creation.
And while collision is simpler in a racer than in HL2, integration has to be a lot more accurate in a racer than an FPS. An FPS just has to look approximately right, but a racer better be able to reproduction acceleration times, stopping distances, cornering speeds, etc., accurately to real-world counterparts or players will gripe.
Sorry, I don't mean to be arguing with every other post of yours.
You don't need complex integration for reproducability. All the things you mentioned can easily match real-world values with simple Euler integration, let alone the far better yet still simple alternatives.
Physics is not hard because of accuracy. HL2 is harder because the types of physics are harder to solve. More objects have the possibility of hitting and being in simultaneous contact with each other. Free bodies have to react to impulse forces many orders of magnitude higher (relative to their mass) than what a car feels. Consider a stack of light, wide boxes, and dropping a heavy ball on top. What happens? In reality, the reason the stack doesn't move downwards is because the
ground provides an instant upwards reaction force. You have to propagate the forces down through the boxes, then back up to the ball. These are all free bodies so you can't take any shortcut or preprogram a particular path through the contact points as I just described. It's not an easy thing to do, and requires many iterations.
Now, for a racing game, you simply model the motion of the wheels independently along the aforementioned single dimension (assuming the car body follows the same trajectory as specified by the last update), then apply forces on the car based on the wheel position and the forces they apply to the ground. You can iterate to make it more accurate if you want, but I guarantee you that nobody in the world will be able to feel the difference playing the game.
Even at a 360Hz update rate and a weak processor like a 386, you have a hundred thousand cycles to spend on a few formulas. The quality of car behaviour has everything to do with the parameters in those formulas, not their calculation accuracy.
I've coded a simple car simulation (though obviously without the car data that PD has) as well as a general free-body physics engine. I know what I'm talking about. For the driving simulation aspect of a racing game, it's ALL about the model. CPU power gets you nothing.
