I have read and keep reading on forums that the high the pressure the lean the tune up.. This only holds true to a point if your guage is off. I have personally flowed more nitrous than I can remember. Setting up jetting patterns and checking customers intakes.
On our test bench once we got past the 1050 psi we saw a nitrous fall off in realtion to pounds.. Now we made jumps of 50psi and for our jetting and our systems 1050 is that magic number that yeilded the highest lbs. lost for 10 seconds...
Now to the chassis dyno, Hp difference on a honda direct port was 1 hp from 900-1050. what does this mean not a lot since not sure the accuracy of the nitrous gauge itself.. Lets face it if the gauge is under 100.00 the accuracy might not be on the chilly, but close enough not to hurt anything....
Now I am no scientist or chemisty or anything like that just a hot rodder, I am sure some other can help with all the math stuff... I just know what the bench shows me..

Now lets see about a cold bottle filled but only has 600psi in it.. That nitrous mixture should be more dense than the hot mixture yet it yeilded less lbs lost. Maybe should set the system to work at that pressure and see if the hp changes do to a more dence charge... hmmmmm




Ricky

 

Good post Ricky. I see a lot of people at the track trying to run 1200 PSI of bottle pressure, not realizing that they're shooting themselves in the foot.

 

These tests have been done by many people many times and a long time ago.

A higher pressure means at least two things.
First is a higher flow rate, or more nitrous per second. Raising pressure is roughly the equivalent of increasing jet size.
Second is that the higher starting pressure means more energy is absorbed at the time of pressure release, or vaporization. This means a colder and denser intake charge in the manifold, and more power.

Pretty much the only downside of running higher pressure is that the smaller bottles will lose more pressure by the end of a run. This isn't always such a bad situation as the engine generally needs more fuel on the big end. If your tune was very close to begin with, then leaner at launch and richer on top can net you even more performance gain by having the tune change dynamically as you make a run.

If your tune is the recommended jetting for the 'kit' at that increased pressure, which is usually at least 15% too rich to begin with, then you're screwed and may very well run slower overall with the higher pressure, though your launch should definately improve.

This is real-world in a car, and not on a dyno or a test bench.

Some people go the other route by running a very large bottle and larger jet, but at a lower pressure which ensures that the pressure will not drop significantly during a run. This gives a very even and consistant tune. There's really nothing wrong with this if you're staying on the conservative side with the tune. It's easier for a lot of cars to hook this way as well.

About the only reason most people would go to a dynamically changing tune would be to squeeze 100% of the performance out of the car.

the only other downside I know about to running higher pressure is that rarely some solenoids do not operate correctly at very high pressures. the bigger solenoids generally don't have this problem.

In summary, the amount of added heat required to increase bottle pressure is very small compared to the amount of heat absorbed when this higher pressure is released. People are not shooting themselves in the foot by running higher pressure.

 

White2001s10, once past 1050 the bench showed less lbs flow... The nitrous liquid changed to a gaseous state less weight left the bottle.. i can not explan completely it just happened, time and time again... I under stand that more pressure usually equals more volume, but not in this case..
Ricky

 

The reason the "more pressure = more volume" doesn't hold true in this situation is that because at approximately 1051psig nitrous oxide undergoes a phase change into a supercritical fluid, it's neither a gas nor a liquid. This means that theroetically any amount of increase in pressure beyond 1051psig will not result in any increase in volume flowed. However, I have seen guys make more hp, less, hp, and have hp stay the same when they increase pressure beyond 1051psig.

This is why Ricky got the results that he did repeatedly.

 

Are you saying that hp was not effected going up and down with pressure? if so wer you changing fuel jets to be relative to pressure changes ie: same a/f. Also, what was the effect on torque? I would say the torque is where the main differences lie? I know as a fact that increasing bottle pressure on a dry hit will yield better ETs, so increase in hp/torque must be taking place.
Robert

 

Maybe your gauge is off and you were not at max rec. pressure to start with..
The honda testing was same curves just less 1 max hp...
Ricky

 

Hey Robert how many kits you got on that.
Ricky

 

Three set-ups that I have personaly done. It just makes sense, more pressure, more n2o going into engine, and being a dry hit and variable reading by maf you maintain your selected a/f whether going up or down in pressure. Should have seen the new best time my buddy ran on a dry when his pressure was at 1300psi (sitting in sun), he got busted for the no roll bar rule. Ricky, by the way, please don't say honda civic on our site, that's blasphemy.
Robert

 

Okay, if i'm going to ask my wife (Microbiogist/Chemist) about this what am I going to say it is is not liquid or gas?

 

I just answered you Macon, haha

 

And so it begins....

 

I personally and others have run in excess of 1500+psi with very significant gains fairly proportional to the pressure increase. Everytime with any configuration I've seen power go up with pressure. That's only been for about 15 years though, so call me a newb.

 

ok newb,, 1500+ really amazing lol and 15years to boot.. and if you double your burst discs, now thats just stupid..
hey do not knock the testing thats what makes the world go around, and I have seen a few hondas goes with the territory..
Ricky

 

Good, calling me stupid isn't helping prove your point. Whatever floats your boat.
No harm to me.

 

maybe there are more variables to be considered here. Like CFM, and temperature

For example

Pushing "x" CFM of nitrous @ 1300psi
Pushing the same "x" amount of CFM of nitrous @ 1050psi but with a bigger jet

which will make more power?

pushing "x" bottle pressure @ "y" temperature
pushing the same "x" bottle pressure at a higher temperature.

which will make more power? probably the cold bottle cause it's more dense, but then again N02 is wierd.

But in real world situations, you probably wont have a temperature AND a pressure guage AND a way to know the actual volume of N02 you're using. I dont have the equipment to make the test or else i would.

 

I'm curious, what size solenoid do you normally use when the bottle pressure is that high? Also, here's something that was brought up by someone else here. By raising the pressure to an excessive amount above the supercritical point you are actually running richer rather than leaner. This could account for the hp gains. So the gain is actually coming from running a little richer tune rather than actually moving more nitrous through the motor.

On a side note, why double the burst disk when they normally rupture at approximatley 2800psi? By doubling that rating you just raised the rupture point of the disks above what the bottle itself is rated at. I personally would much rather have the burst disk let go instead of having the bottle explode. That wasn't a bright idea at all.

 

This is why I chose to use elctro temp transducers on my heaters, instead of pressure based mech transducers. A thermo transducer at 85* will heat bottle to 950psi, and a 95* thermastat will heat a bottle to 1150, which I run.
Robert

 

But what about when the bottle runs low. Wont it have lower bottle pressure @ 95º?

 

Oh yea, when it no longer will heat past 800psi it's time for a refill, no more weighing to figure out where I am at. Works great for a dry set-up as the maf can figure this out. whereas, a wet your prob better off with a pressure based transducer that will heat what ever to pressure, but no way to know when getting empty.
Robert