How important is bottle pressure?

As I use up the N2O and bottle pressure drops - can anything bad happen to my motor? In other words, can I keep spraying until I run out of N2O or do I need to stop and refill the bottle when pressure drops to some number (say 500psi). Will it just start running rich with no harm done? Fuel pressure should stay constant and jets aren't going to change so as pressure drops I guess it justs to run richer and richer.

This is a street engine with up to a 150HP spray on a plate system. There is a N2O pressure gauge on my dash pod.
Will a bottle heater keep the pressure consistant (say at 900psi) until I run out of N20? Is that purpose of the heater?

Remember that pressure is not directly proportional to content remaining.

Pressure affects the tune up, it is very important IMO. I try to shoot for around 950psi before I stage, its usually at or above 900psi after the run. Dont leave the pressure on the solenoid any longer than possible. I dont fill my bottles all the way up, I usually only go 9 lbs........seems to make the pressure not fall off as bad as one thats at full or over capacity. I dont use a lot but after 3-4 passes I put a fresh bottle in.


A side note you'll never get all the nos out before it flashes to vapor inside the bottle..............in other words a 25# bottle you wont get usable nos at 15.5#s, usually somewhere in the 18-19 # total weight the liquid is no more.....................

Pressure and volume are important. You want to maintain a consistent pressure at the start of each run. The volume of liquid in the bottle will in part dictate the pressure drop you'll see during the run as the bottle relies on this liquid to boil and help regenerate vapor pressure during the run. From what I commonly see once you take about 50-60% of the liquid out of the bottle, you'll see larger pressure drops.. Hope this helps.. SJ