383LQ4SS

iTrader: (33)

Theres alot to this question of pressure and flow. Normally its higher pressure = higher flow through a given orifice. But in this instance we are operating with a gas that will change properties rapidly...and sometimes more than once.

Stored in a bottle at 1000 psi its liquid
coming out the nozzle its a "fog" of liquid rapidly becoming a gas
over 1050 psi its a supercritical phase shifted "soup"

Definately makes it difficult to predict behavior and density as its flowing from high pressure to low.

If the nitrous does go supercritical at 1050+ psi than of course the flow will drop. The reason is that the liguid nitrous that normally flows out at 1050 and below is much more dense than the supercritical soup of just above 1051 psi. At that magic point you have just redistributed all the nitrous mass that was in the vessel equally over its interior. So the avg mass per given cubic inch (density)has just dropped probably 50% (guesstimate). But I bet that the flow of mass over time is not reduced 50% since the flow velocity rate picks up with the less dense suprcritcal n20.

So if this is somewhere close to being true...you would see a drop in flow from 1050 to 1051. But at some point it seems you again would begin to get more mass flow over time as pressure increases. Probably right where the higher pressure is increasing flow of the supercitical n20 enough to compensate for the reduced density. Who knows what that would be...1200,1400,2000....

Then you have to think about the fact that the supercritical nitrous flowing out the bottle valve will amost instantly recombine to non critical before it gets to the nozzle when the noid is open. When and where that takes place will be dependant on how high the pressure was in the bottle to begin with, the lenght and volume of the line, temp, the size of the orifice at the other end and velocity of the nitrous through the line.

This whole thing is too much to fathom. Funny thing is there is probably a text book somewhere with formulas to figure all this crap out.


I think for a wet kit its just best to stay within the manufacturers specifications to be consistant. Whatever you do though just be sure its the same everytime. As Ricky said...I would not be raising my bottle pressure from 1000 to 1200 to compensate for a rich condition. Thats better suited to a jet change.

white2001s10

iTrader: (4)

It was NOS part# 16000 or sometimes known as the Cheater solenoid is what I use most of the time because I've had great service from them so far.
I was definately running leaner with the higher bottle pressure. There is no question about that at all.
I've been to both extremes more than a couple of times.
My power tuning has always shown more power the leaner you go, even up to the point where you start melting ground straps on the plugs. Anytime I've increased fuel I've measured a power drop.
I'm not speaking for anyone else right now, just my own results.

I was also surprised to learn something about burst disks. They aren't all rated at the same pressure. Some are made of different materials, and third is that the pressure that they blow at changes with temperature. The hotter the disk, the less pressure it takes to pop one.
I've never told anyone else to run two disks. That's my business.
Anytime you mess with pressurized gas you are in danger, and I'm well aware of that part.

At no time did I tell any other poster here that they were wrong about their own testing. I just stated that my testing methods were different and that I got different results. I didn't expect that would be unwelcome.

As far as I'm concerned, the more testing the better. Eventually someone will learn something new.
If Ricky's test results conflict with mine and others, then maybe the reason for the difference will uncover something new.

Ben R

Your power gains were found because increasing the bottle pressure to 1500 (Read, decreasing the amount of liquid nitrous 'fogged' into the cylinder) you ran a N/F ratio that was more effecient for making HP.

860 Performance

iTrader: (1)

I’m reading this post and this topic has always interested me, and was wondering what would be a good accurate way to test this out. I have some special 12V one-shot adjustable time delay relays which can activate a solenoid for an exact repeatable amount of time, and an accurate scale. So… I wired up an NX purge solenoid (.062 oriface, or about a 150hp shot) directly to a full 10lb bottle with a flow-through manifold and a pressure gauge. I figured if I set the bottle pressure to 800,900,1000,1100,1200,1300 psi filling the bottle between tests, I can measure the amount of nitrous used in each test to determine what pressure flows the most mass. Pretty simple accurate test.



So I set everything up and figured I’d start at the highest pressure then work my way down. With the bottle warmed up to 1300psi, I set the time delay relay to exactly 10seconds and fired it off. What I immediately noticed was the pressure droped down right away to around 1,000psi and by the time the 10 seconds were up the pressure was stable at 975psi. It stayed at 975 after the nitrous stopped flowing.

So even though N20 gets funky above1050psi, as soon as it starts to flow the pressure dropped below that point. As long as you are running a good sized shot, I think its ok to keep your ‘static’ pressure above 1050.

I only did the one test and stopped there after seeing the pressure drop and figured we could discuss before I wasted more nitrous.

I have some pics I took with my phone camera, I’ll post them if I can figure out how to do that out.
Vinny

383LQ4SS

iTrader: (33)

when did you do this test? Is it still setup?

Can you do it with a 15 lb bottle and maybe put a jet in for a 50 shot and reduce the time to 5 seconds and repeat the test?

Robert56

iTrader: (2)

I have/or had the math for pressure relation to hp/flow/temp, and I'll see if I can find it.
Robert

white2001s10

iTrader: (4)

Just curious here. Did someone call you over so you could post this and add the laughing smiley for me?
That's sweet of you to come and tell me exactly what I was doing.
Thanks!

Stupid me. I was making much more power by using less nitrous. I'm such a moron.
I should of read up about this supercritical mass theory you guys have explained to me. I'll do more homework next time.
Where the hell was the internet when I was learning this stuff wrong with practical tests?

cyipher

iTrader: (1)

How about a bottle at 1050 psi at 30 degrees F? nitrogen push is the only way i know of doing this but it would be interesting to see if there is a hp difference.

383LQ4SS

iTrader: (33)

White...if you missed it. I happen to agree with you to some extent. I think you get more flow as pressure increases. Then right at 1050 it may take a step backwards...but I think as you continue to increase pressure again it continues to rise.

Id like to see the tests done at 800/900/1000/1100/1200/1300/1400/1500 just for reference. I personaly think you will see a steady gain in flow at each level except maybe a platue between the 1000/1100 range. But then continue to climb after that at some point.

NXRICKY

iTrader: (1)

I think everyones testing from one point of testing to another can very, just posting what I saw. The way 860 describes is how our bench is set up, so to take out as much of the oooopssss factor as you can... Also our testing with the .093 and the .125 noids from a stage one efi to a direct port kept showing the same type of results..
But alast thats not the end of the story... With a direct port you can go from a 600hp shot to a 400hp shot with just the wrong style of fittings.... So there is a lot to learn and for each person the knowledge he or she has for there car is warranted and I would like to think welcomed, as long as its not puting two blow off discs in one bottle.. Man be carefull with that, would hate for anything bad to happen just becuase of that. happy racing to all and to all a good night.
Ricky

Matt@HSW

iTrader: (14)

I’ve been working with this for quite some time now…still a work in progress so bear with me. Now if you are to base nitrous efficiency solely off of volumetric flow rate then the obvious result would be that higher pressure would yield better results. As seen here: Vdot = A(v). Increase the jet size (area) yield more volume flow, increase the velocity yield more flow also conversely true. However, volumetric flow rates neglect some important aspects of thermodynamic efficiency…ie density, the mass per unit volume of a substance under specified conditions of pressure and temperature. Density is a very important factor in achieving efficient nitrous delivery. For example, here are some densities of nitrous at pressure/temperature (attached below).

As you can see density severely improves as temp/press go down from the critical point. However there is a breaking point. The problem is that you’re decreasing pressure which as a resultant loses velocity, another important factor in volumetric and mass flow rates. I feel that one needs to view the mass flow rate of nitrous more so than volumetric and to do this density is a must. Mdot = Rho(Av). Can also be written as: Mdot = Rho(P1 – P2)/R , where Mdot is Mass Flow Rate, Rho is density, P1 and P2 is change in pressure, and R = (8(n)(L))/(Pi(r^4)). Visually it’s easy to see what happens when you plug different numbers in…density and pressure are going to fight each other. Physically and mathematically speaking, you can achieve poor results with too high of pressure and too low of pressure. At 600psi I think you will see a slightly poorer result than at normal bottle pressure only because the density change cannot make up enough room for the pressure change. As far as what pressure nets the best thermo efficiency, I’m still working on that, but 900-950psi seems to net positive results. Keep in mind, and as Ricky pointed out earlier, just because your gauge reads XXpsi, does not necessarily mean that a) its accurate and b) that’s what the pressure is at the solenoid(s) and nozzle(s). I’ve seen poorly plumbed systems drop in excess of 200psi from bottle forward. I would be interested to see your results Ricky, keep us updated.

Nick

860 Performance

iTrader: (1)

Great info on this post! I didn't realize how much the density of the liquid changed.

383- I did that last night and its still set-up.

cantdrv65

iTrader: (3)

Al 383LQ is right on in his thinking...I believe after you see the phase shift to supercritical state right around 1050 psi you will certainly see a decrease in mass flow. How much of which Im not certain. After that point as you increase pressure, flow HAS to increase therefore at some point you will again flow the same amount of N2O to the engine. As for the temp change someone mentioned of the N2O in the bottle....Believe it or not once you reach the supercrtical point temperature ceases to matter at least in the bottle. Once you hit approx 1050psi in the bottle you have a supercritical state period, no matter the temp. Also when measuring pressure while flowing you must have the gauge before the first restriction(bottle valve) in order to see the actual pressure in the bottle. Is this the way Ricky and 860 have set up the test? If so I think this is an excellent test experiment and is the only real world way to tell what is actually going on with pure N2O flow. An engine and power gains or losses again introduces too many variables. BUT, not only will each of these variables change slightly for jet design, it will also change for jet size. Fun stuff guys.....

cantdrv65

iTrader: (3)

Great post by Matt! Now we know the actually density loss when N2O goes supercritical....Since it loses so much density at the supercritcal point it seems reasonable you would want to stay just below it to get the most density directly out of the bottle. Which as it is, guess what, all manufactuers appear to be! That is unless you are crazy like white and want to just jack your pressure up to infinity. Good info by all.

860 Performance

iTrader: (1)

I agree pressure should be measured in the bottle before even the valve. The NX pureflow45 bottle would work for this since it haqs the portsd in the bottle, but its not the way I did it last night. But, seeing as though the pressure after 10sec of flow dropped down to 975psi that is certainly below the 1050mark.
It seems we need to measure bottle pressure when flowing. Because we always talk about bottle pressure as a single number.

For example: If whites10 runs 1500psi in his bottle but then runs a 500hp shot, his flowing his pressure might be only 900psi (just a complete guess), over the magority of his run. Point being- he is back below the 1050mark.

I think the next good test would be to record bottle pressure at a good sample rate of a few recording per second at few at different shot levels, starting them all at the same starting bottle pressure.

Ben R

You only wish you were that important. I put the laughing smiley because I found it humorous that you are doing things 100% backwards, and you're telling people it's the right way.

Admitting your problem is the first step to recovery.

Ben R

Bottle Temp °F Bottle Pressure (psi)
-30 167
-20 203
-10 240
0 283
10 335
20 387
32 460
40 520
50 590
60 675
70 760
80 865
85 950
97 1069

Ben R

Great post here Nick. What's important here is that we look at the systems overall effeciency. Measuring bottle pressure at the bottle via a Racepak computer is not the way I would recommend.

A few months back I had a very long discussion with one of the best nitrous tuners in the country (Think Pat Musi good) and he told me they have Racepak sensors measuring bottle pressure at the outlet of the bottle, before the solenoid, and after the solenoid. Part of this is done with Edelbrock in an attempt to design a more effecient nitrous system. It's also done to help them fine tune their system. They run the systems so close to the edge that the margin for error is very slim. They do the same thing with the fuel side of things. If they could measure pressure as the N20/Fuel were entering the nozzle they would do that too.

Another thing most people overlook is the way the system (speaking of a fogger here) is plumbed. A lot of times people don't realize that they're asthetically pleasing fogger kit is actually costing them horsepower and repeatability.

Nitrous is being used by some of the smartest guys in the industry, and they're using computational wet-flow systems to design distribution blocks and nozzles. It's pretty scientific stuff now-a-days.

95ttoplt1

iTrader: (3)

So from all of this I have developed a question, where would the pressure be the most important? I would think if you were 1050 at the jet its self would yeild the best flow as long as your plumbing was big enough to flow the supercritical juice that far? Also for those of us that only have one pressure gauge, where is the best place to T it in, and do we go for a staic or flowing pressure?

Ben R

For anything that isn't a real racecar where the tune-ups have to be 'on kill' putting the pressure guage just after the bottle is fine. You won't see bottle pressure until the bottle is open, and when you click the solenoids open you will see an initial pressure drop and then pressure will continue to decrease throughout the run. This can be minimized by many different things, but for a street car it isn't that big of a deal.