Nitrous / Purge Lines

The purge is used to get the liquid nitrous right up to the solenoid. The liquid causes the cooling (like A/C) when it changes state to a gas. The heat in the engine bay will cause the the nitrous to turn back into a gas after a while, so you need to purge out the gas right before each pass. With out the purge the car will run rich (and slow) until the liquid from the bottle works its way forward. It looks like it is just for show but it is necessary to make a good pass.