stk-code_catmod/data/gfx/kart_exhaust.xml

<?xml version="1.0"?>
<particles emitter="box" box_x="0.05" box_y="0.05" box_z="0.10">

    <spreading angle="2"         />
    
    <velocity  x="0.0"
               y="0.005"
               z="-0.01"         />
    
    <material  file="smoke.png"  />
    
    <!-- Amount of particles emitted per second -->
    <rate      min="200"
               max="300"          />
    
    <!-- Minimal and maximal lifetime of a particle, in milliseconds. -->
    <lifetime  min="10"
               max="40"           />
    
    <!-- Size of the particles -->
    <size      min="0.05"
               max="0.1"         
               x-increase-factor="5"
               y-increase-factor="5"
               />
    
    <color     min="255 255 255"
               max="0 0 0"  />

</particles>