>I'm writing a car racing computer game.
>In order to simulate the cars, I need some values for the car's
>parameters.
Lots of luck; I believe that 99% of the people who start this task
vastly underestimate its scope and fail to complete it. Not to
discourage you, but do have a realistic look at whether you are
skilled enough and have ENOUGH TIME to complete it.
Look in Road and Track, or the equivalent magazines, or go to a BMW
dealer. The sales pamphlets for the car will often have a horsepower
or torque curve for the motor. From this, you can derive pretty good
estimates. For a street car, assume 30% loses in the drivetrain.
I'll answer your question, but if you use the first part of my answer,
you'll REALLY be wasting your time. 1.1 or so, but could probably
range for 0.9 to 1.4. This varies far more by factors that you are
probably unaware of (slip angle, % slip, unit loading, etc.)
You really need to read a lot about tires, for the tire/road interface
is probably the most complicated part of getting the whole simulator
to feel "right." The only simulator released to date that has even
close to the right feel is [Hard | Race] Drivin' by Atari. Even the
Papy sims (to date :-) ) don't really get it completely right, despite
plenty of effort. GPL on the other hand...
1.0 G of deceleration. Thus, whatever the mass of the car is
multiplied by acceleration due to gravity in your chosen units. This
is largely independent of speed, but quite dependent on wheel loading.
Cd of somewhere around 0.33, but this is likely in the sales pamphlet
and in the car mags. This is quadratic with speed.
This is likely to not be in the mags, but might be (unlikely) in the
sales pamphlet. Most street cars probably generate negative downforce
at speed, as an accident of their streamlining. In any event,
aerodynamic loading for a street car is probably not much of a factor
until speeds of 75mph or so. This is quadratic with speed.
I've taken a shot at it, but you need to know a lot more than it
appears you do. It's not insurmountable, but it's a hard climb if you
don't have a solid math and engineering background.
Uhoh, long, hard road ahead...
Those are the natural (English) units for torque. Divide by the radius
to get the force in lbs. (300 ft-lbs operating at a radius of 2 feet
provides 150 lbs of force.) This question indicates a lack of
mechanical engineering background. To get a good simulator, you're
going to need some mech E background, or at least have access to a
patient person who does...
Load Index is a term that I'm not familiar with without the benefit of
the surrounding context. It probably covers the fact that a tires
coefficient of friction DECREASES with increasing unit load, but
again, with no context, it could be an English term for something I
know about, or it could well be one of the many things I still don't
know about tires...
---Jim
