Tryiing Finetune with TFD

I have a little Problem here. I made a Setup for a Explosion and i have toi Setup the Settings.

As soon as the Cloack gets Transparent the Programm is still rendering the Transparent Parts.

Can i somehow Clip the Settings with the Curve ?
I tried one. At 0/0 iput the Settings a little higher. But the Only Thing that has happended was that the whole Container was a Grey Mask.

I must somehow set the Transparency to Zero, that the Card or the Prozessor does only need to render the Opaque Places. One Frame costs me at least 9:50 Minutes. And i have 600 Frames. The Clouds is getting right, but the Transparent pieces are still rendered.

Set the left hand point on the density graph to 0.01 or 0.001 on the x axis
My Tutorials