Ok so what GooseF22 said makes sense.

The old J79 smoked due to lower than optimum temps during combustion.

As most of our turbines have combustion chamber temps above 700C (EGT =650C + so combus temp must be higher) so no smoke.

For Todds issue as he does not have to deal with AMA legalitys so if one could make a mini afterburner that fed Kero and burned at a lower temp he might get black smoke. IE a little can with a flame holder attached to the end of the stainless smoke tube, it would be interesting to try on the bench.

Aloha

Duke