Depends on engine curve, the one I’ve found were all in N*m, so conversion is just multiply by 100.
If you have some gear connected after gear box but before deferential - then yes. The point is to select some part of transmission as a reference for integrating angular velocity, I choose to do this right before differential and reverse gear (actual mechanical gear) as left and right track can be rotating with different velocities and in different directions. This way axle always rotates in the same direction, regardless which way tracks rotate.
angular_acceleration_of_axle = Torque / Moment_of_Inertia_of_Transmission; wheels are not involved in anything yet, at this point we are rotating clutch-gearbox-axle, so we need their moment of inertia, not wheel’s. I calculated MOI offline using simple primitives and guesstimation.
angular_velocity_of_axle = angular_velocity_of_axle_on_previous_frame + angular_acceleration_of_axle * delta_time; that’s what it means by continuously integrating axle velocity, we keep track of it on every frame and capture any changes that happen to it.
Relative velocity consists of two part: linear velocity from car’s movement and linear velocity from wheel rotation. First one you ether calculate yourself by taking into account linear and angular velocity of the car or just use GetVelocityAtPoint() function.
Linear velocity from wheel’s rotation is simply wheel angular_velocity*radius. Both terms give us a complete linear velocity of the wheel at collision point, but as collision surface can be sloped and wheel might be moving not in parallel to it we need to project everything into the plane defined by collision normal. Final expression will be like this:
Wheel_velocity_at_point = GetVelocityAtPoint() - Car_X_Vector * (wheel_angular_speed * radius);
Relative_wheel_velocity = ProjectVectorOnToPlane(Wheel_velocity_at_point, Collision_Normal);
It’s a bit more complicated as friction might not be aligned with the X axis of the wheel. After you got friction force you project it first to the X axis of the wheel and only then you calculate torque from it.
It’s not about limiting RPM but limiting Torque, without red zone you will be always getting torque at top RPM, so you will be accelerating without need to shift gear.
Velocity doesn’t convert into force, “propulsion” comes from friction force resisting movement of the wheel, you could take into account torque in friction calculation but together with wheel’s velocity.
Hope this helps!