Hardware:
Processor: Intel Core i7-2600K @ 3.40GHz (4 cores, 8 threads)
Memory: 8192MB, Disk: 256GB Samsung SSD 840
Graphics: MSI NVIDIA GeForce GTX 570 1280MB (732/1900MHz)
Software:
OS: Ubuntu 14.04
Kernel: 3.13.0-32-generic (x86_64)
Desktop: Xfce 4.10
Display server: X Server 1.15.1
Display driver: NVIDIA 331.38
OpenGL: 4.4.0
Screen resolution: 1920 × 1080
Game is in 1920 × 1080, fullscreen. Compositing (desktop effects) of Xfwm is enabled. The track used is I6-Flooded, at start position with default camera settings.
Default settings (the ones used when you first start the game):
110 FPS. 117 FPS with static car reflections (+ 7). Disabling water reflection and reflection goes to 140 FPS (+ 23). Disabling shadows goes to 178 FPS (+ 38).
FPS with different shadow sizes, from lowest to highest: 146 FPS, 145 FPS, 142 FPS, 138 FPS, 122 FPS (with shadow count 2). Thus, 1024 shadow size is the most efficient one. Using 1 shadow instead of 2 makes distant shadows uglier, but is only slightly faster. Using 3 shadows is slower for no benefit.
FPS with various graphic presets (after a track restart, so all presets used the high-quality textures):
Lowest: 431 FPS
Low: 371 FPS
Medium: 194 FPS
High: 135 FPS
Higher: 100 FPS
Very high: 75 FPS, without effects: 99 FPS
Ultra: 45 FPS, without effects: 66 FPS
Impossible: 25 FPS, without effects: 53 FPS
Playing the game with Impossible preset is actually possible, Stunt Rally doesn't need very high FPS after all.
Effects:
Lowest + all effects: 42 FPS
Lowest + all effects but god rays: 80 FPS
“God rays” is a very expensive effect (disabling it gives you + 38 FPS), it's buggy anyway and generally does nothing.
Vegetation:
It seems to be hard to get reliable data on the performance impact of vegetation, but using the “Impostors only” setting will be quite faster, almost as fast as disabling all trees. However, with this setting, trees won't cast any shadows.
You too can try contributing by making your own benchmark like that one. Just test all presets, changing from one preset to another, then pressing F5 to reload the track.