Wow, that's a lot of interesting questions! I'll try to answer some of them. By the way, you probably already found it, but there's a description of the car parameters here:
http://wiki.vdrift.net/Car_parameters
I recently rewrote the car physics code so on the plus side it's on my mind but on the down side I'm sure it has a lot of bugs.
Tires:
As you noticed you can adjust all of the pacejka parameters in the .car file. The only thing you can't adjust is the way that the longitudinal grip (accelerating/braking) and lateral grip (cornering) are combined. The basic pacejka equation models each separately, and it's up to you to figure out how to combine them. I use a combination algorithm that Brian Beckman came up with and describes here:
http://www.miata.net/sport/Physics/Part24.html
The relevant function is CARTIRE::GetForce(). The Beckman method sort of pre-combines them by scaling the inputs to the individual pacejka functions. If you want you could try modifying the function to not do that and then try one of the post-combining schemes that's currently commented out.
Noises:
At the moment, the only supported noises are road noise, a "bump" noise that plays when the suspension compresses suddenly, a crash noise, tire squeal/dirt noises, and engine noises. If you're in a hood or driver view, most of the sounds play without any 3D positioning effects (which are expected to be baked into the sound file), otherwise they're put at the center of the car (the tire squeal/dirt sounds are always put at the wheel locations). I'd like to add a lot more noises but just don't have them. The engine noise can either be an engine.wav file that's in the same folder as the car (in which case it needs to be 7700 RPM), or a bunch of separate files. For an example of the latter, check out the TL2. It's got a sounds folder with wave files in it and a TL2.aud file that has a very similar layout to the GTR type .aud files.
Controller calibration:
No old-school joystick calibration options are used by VDrift anymore (you should use your OS's calibration tools), but individual controls can be adjusted for deadzone, gain, and exponent. To make those adjustments, just go into any "assign controls" type screen in VDrift and click on the little joystick icon for any control that you've added. It'll pop up a screen with adjustment sliders.
Button delay:
Good idea about making the "off" delay ramp out faster. The code for button ramping is in CARCONTROLMAP_LOCAL:
rocessInput(). One of the arguments that is passed in when this is called from game.cpp is the button ramp setting. It's used by the joystick button handling code to be passed into Ramp().
Engine inertia:
I think you've figured this one out. There used to be a separate setting for the engine friction (torque-friction) but I now ignore that setting and compute a value algorithmically in CARENGINE::SetTorqueCurve():
Code:
friction = max_power / (max_power_angvel*max_power_angvel*max_power_angvel);
That section of code in cardynamics.cpp@478 is ignored; frictionlimiting is always false so that block never executes -- so just ignore that.
First, there are a couple of parameters in the .car file that could be interpreted as wheel inertia: first, the mass parameters in the wheel sections, and second, the rotational-inertia parameters in the tire sections. By the way, you can see how the .car parameters map onto the car physics classes by looking at the mammoth CAR::LoadDynamics() function.
The mass parameters in the wheel section are used only to add to the computation of the body's inertia tensor and weight (unsprung weight is not simulated separately). The rotational-inertia parameters in the tire section are used by the physics tick of the ROTATIONALFRAME inside of CARWHEEL. This is the simulation of the rotation of the wheel in its forward axis only -- forces (from the engine, from the brakes, from the road) are applied to speed it up or slow it down, and it reacts accordingly based on its inertia. Don't set this too low or the whole simulation breaks down and you'll get wacky results. When I fiddled with the inertia parameter I found low settings caused more wheelspin when starting from a stop -- I think this is just because the engine can spin its wheels with less work and get them past that ideal, maximum-force longitudinal slip %. With a high setting it takes forever to accelerate. I'd expect a lower setting to make the brakes lock up more easily. What were you expecting?
Yes, the inertia could be calculated based on the wheel mass and radius by assuming a cylinder: inertia = mass * radius * radius * 0.5... but that seems to give too low of a value, so either my units are off or the rotational inertia of the other components of the driveline that need to be added in (diff, axle, etc) are much larger than the wheel inertia, though that seems kind of absurd.
