The following part can be inserted into a mod's vehicle xml ("motorized" section) to modify the behavior of the smoke.
Attributes and individual factors can be left out when you don't want to override them.

<exhaustExtension excludeVehicle="false" intensityFactor="1.0">
    <motorStart factor="1.0" timeOffset="1.0" />
    <cutTree factor="1.0" />
    <delimbTree factor="1.0" />
    <engineLoad factor="1.0" threshold="0.5" />
    <nodeOffsets>
	<nodeOffset offset="0 0 0" />
    </nodeOffsets>
</exhaustExtension>

- By setting "excludeVehicle" to true, the current vehicle will be excluded from the ExhaustExtension script. 
- With "intensityFactor", you can modify the overall intensity of the smoke for this vehicle.
- "nodeOffset" controls the offset (x,y,z) from the basegame exhaust effect. You can add multiple "nodeOffset" entries when the vehicle has more than one exhaust effect.
- engineLoad threshold (0.0 - 1.0, default: 0.5) is the load value where the particle effect starts