R particle tracelimit
From FTE
Name: r_particle_tracelimit
Default value: "250"
Flags:
Stops particles from using traces if there are lots of particles, it can cause particles to drop out of the level, but on the plus side, it can stop 10000 particles from churning your computer too much.
It is not quite a "max particles" limit, you will still get particles, but with less slowdown.