Topspeed modifier

[freeman2344]

Hi,

how does the "topspeed=" modifier in the "gearedfor" section work? I have tried to set this infinitely low just to see what it does and it does not seem to bring down top speed significantly. Same goes for acceleration. Care to shed any light on this?

[Frankschtaldt]

In my fiddling I have found that many of the stats for individual components have a very small effect on the overall end result.
From what I can gather the game builds an aggregate multiplier from a number of different sources and applies it as one big number meaning that changing the number on one component has a very small overall effect.
So, in the top speed equation it might look a little like: top speed = (complex equations taking into account weight, power and drag) x (100 + (topsspeed= from gearbox) + (topspeed= from vehicle type) + (performance focus slider value)) etc etc.
The end result is that changing the number on one component has a very small effect unless you change it by a vary big value. If you want a slow gearbox try setting it as a negative value. When I was playing with my mod I set quite a few engine values at negatives to get the results I was after.

[Eric.B]

The topspeed modifier has been greatly reduced since I redid the top speed calculations for 1.12.

As it is now, it effects the performance rating of the gearbox, which gives a 1/16th bonus to the calculated top speed.

So pretty much as of now, it's nearly useless.


I still have a little adjusting to do in these numbers as evidenced in one of frank's posts. I will try to bring more gearbox numbers into the top speed as it was in previous builds. Hopefully without breaking anything more than it's broke!

[freeman2344]

Ah, that explains a lot, actually...if you have the time, would you mind deciphering to what extent certain components influence top speed and acceleration? Weight verifiably has an influence on acceleration, but how is "performance" actually defined in Gear City? Is it like top speed and such or rather handling characteristics? Maybe a combination of both?

[Eric.B]

As of right now the variables are:
RPM
Torque
Gear Ratio
Drag Coefficient
Gears
Gearbox Static Performance Rating.

It is then checked against a MaxSpeed possible speed formula: HP^(1/3) * 28*1.60934

And then it's checked against Terminal Velocity of the body: Drag * Area * 1.1644 * Engine Torque

If MaxSpeed > Terminal Velocity
Max Speed = Terminal Velocity


If Topspeed > Max Speed
top speed = max speed



This is subject to change of course. When the game is closer to finish I'll probably (not garenteed though) publish the formulas with mod tools.

[freeman2344]

Sounds great, thanks for your quick answers (as usual)!

[Kubby]

And then it's checked against Terminal Velocity of the body: Drag * Area * 1.1644 * Engine Torque

There is something wrong with this formula. I mean, does really Terminal Velocity of the body increase with drag or area? Common sense tells me it is somewhat wrong.

I think MaxSpeed and TerminalVelocity could get merged into one MaxSpeed value:

V = (P/(Cx*0,6461*A))^(1/3), where

V is MaxSpeed (in meters per second)
P is power after applying drivetrain losses (in watts)
Cx is drag coefficient
A is area (in square meters)

Formula does not take the rolling resistance of the wheels into account (as it is somewhat more difficult to take both of them into account), but it should be close enough, as tested on my own car values.

[Kubby]

Alternative formula, taking the rolling resistance of the wheels into account:

v=(P/(Cx*1,2922*A)+D^(1/2))^(1/3)+(P/(Cx*1,2922*A)-D^(1/2))^(1/3), where

v is MaxSpeed (in meters per second)
P is power after applying drivetrain losses (in watts)
Cx is drag coefficient
A is area (in square meters)

D = (((m*9,81*Cr)/(Cx*0,6461*A))^3)/27+((P/(Cx*0,6461*A))^2)/4, where
Cx, A and P are the same values as in previous formula
m is mass of the car (in kilograms)
Cr is rolling resistance for the wheels (0.01 - 0.015 for modern ordinary wheels, might be more for older ones)

It does not take the downforce into account though. However, it is relatively easy to account for it, if you want to go into such detail.

[Eric.B]

Implemented Kubby's formula from irc.

Thanks a bunch kubby, it works much better now. I will throw in a few modifications for gear-ratios and tweak aerodynamic drag some