NITROUS OXIDE ( nos / n2o ) advice forum

In a full nitrous bottle, how far up the bottle will the level of liquid nitrous be at average ambient temperature?

I'm asking the question as i'm trying to figure out why my nitrous seemed to stop flowing on a recent pass (at 100ft out the engine went flat and O2 sensor shows it going off the scale rich). The only thing that was different on that pass was i couldn't get the bottle quite full (7oz short on a 2.5lb bottle) and wondered if the dip tube may have been exposed to vapour rather than liquid. Seems unlikely as there is still 1lb in the bottle when weighed?

I would expect (but can't be 100% certain), that when full the liquid level would be approx 2/3 to 3/4 full and I would expect it to be about 1/4 full when there's a pound left. Now that may sounds strange but you have to remember that as the liquid is used up, more of it converts to gas, which means a bigger percentage of the weight is gas and therefore a smaller percentage is liquid.

Do you know what the bottle pressure was?

Do you have the bottle mounted with the valve at the bottom or top?

Have you considered the possibility that the nitrous solenoid shut off for some electrical reason?

Thanks for the reply.
No, it's not strange at all, I wasn't sure how much space was allowed for expansion, and guessed that it would be fairly low when down to the last lb, and I've just re-weighed the bottle empty and it only had 11oz in it so even lower in the bottle. I know the dip tube is about 1" from the bottom, and allowing for g force pushing the liquid to one side and it's quickly becoming a possibility it gulped gas not liquid? What do you think?
I don't suspect anything electrical as it all checks out in the workshop, can't find any poor connections, and have never had issues before. It's very consistent normally. Pressure at the start was 900psi and I don't monitor pressure but can see it getting richer on a run so know it's losing pressure and at the end of the track its down at 750 usually.

At very least at 11 oz it was likely to be picking up VAPOUR (part way between liquid and gas), instead of 100% liquid which would have caused it to run richer.

Cheers, i think i'll go with that as the most likely reason it suddenly went flat.
It's 2.5lb bottle and i fill it every run, but it was a hot day and i found it hard to decant enough to fill it fully. It was the only thing that had changed from the previous run that i'm aware of.