Fluid systems - damage models?

[Luno13]

I think the thickness of the thin smoke you are referring to is caused by two layers of the regular thin-smoke texture (smoke in il-2 is rendered in 2-D, but always faces the camera to look more voluminous; this was important to save resources).

The two layers are coming from the engine and possibly fuel tank, or both from different parts of the engine. Because they are in line with each other, the smoke looks "thicker" even though it's the same texture.

This doesn't happen with most other planes. As such, there are still only 3 classes of fire: thin grey smoke, thick black smoke, and fireball. The only thing that really varies is the damage it does and how long you have until you explode. Still, it's not bad for a really old game.