My CS C-130 engine smoke effect lost, even in ACE, every model with engine smoke effect activated.
is there any necessary condition needed to activate the engine smoke effect? such as specific oil temp? weather? altitude? or ..?

I did see smoke on some model and on the other models there are no smoke. I try to use c-130 ACE to figure out what is the different between those models and try to activate the engine smoke effect. I found the smoke one with paint specular middle and the no smoke one with paint specular low, so I change the low specular to middle, then the model without smoke effect before became smoke. I thought I found the key, but I am wrong. I tried to change in ACE for many times but fail.   

anyone can help?