Nitrous pressure should be kept consistent to obtain optimum performance. All NOS systems are designed to work best with a bottle pressure of 900-950 PSI. Pressure is determined by the amount of nitrous contained in the bottle and temperature. The chart below shows what happens to nitrous at various temperatures. Accordingly, it's a good idea to use an NOS bottle heater and/or blanket. Likewise, maintaining consistent line filling is important...which is why most racers use an NOS purge valve to release nitrous vapor from the feed line. This provides liquid nitrous to the inlet of the solenoid(s) for better consistency and repeatability.