Been playing around with my 225LX and decided to turn the pre-flow knob up to
2 seconds. After about an hour I noticed my tungsten was still sharp and contamination free (A first for me). I've had the post-flow set at 2 seconds but never bothered with the pre-flow.

So, I'm thinking I should have been using pre flow from the beginning.

Is 2 seconds about average.

Welding mostly stainless with argon at 12 cfh