20Silverado03

What is it? how is it defined? why is it important?

I finally figured out that fuel pressure is the resistance to the flow of fuel from the pump and that pressure is defined as resistance to flow.

Does the same definition apply here? I want to learn as much as I can.

MaroonMonsterLS1

Your idea of fuel pressure is not quite right. You're describing pressure head.

Fuel pressure, nitrous pressure, air pressure in your tires are all in the same units. Force per unit area.

Usually measured in psi (pounds per square inch) it's easy to see what these units mean. I could give a big physics lesson incorporating kinetic energy of molecules, and use analogies to make sense of it, but I don't think it would be of any real benefit here.

A simple visualization is a hydraulic piston with 1 square inch of surface area. Of you pressurize the fluid to 80 psi, the rod would exert 80 lb of force. Up the pressure to 300 psi and the rod would exert 300 lb of force.

If that's enough to describe what pressure is, what is your real question. Are you wanting to know the effects of more or less bottle pressure or??

20Silverado03

so why does fuel pump flow go down when fuel pressure goes up?

MaroonMonsterLS1

Pump flow in detail can get pretty complicated but a simplification is, as pressure increases, volume decreases.

This happens because it takes more energy to create a larger pressure differential. Energy that was previously used for moving a larger volume.

Imagine a balloon. Initially, when the balloon is empty, you can move ALOT of air into it quite quickly. Your lungs don't struggle at all to double the size of the balloon in a single breath. However, once the balloon is full of pressure you can feel your lungs straining against that pressure.

A fuel pump feels the same way. However, that is a very broad generalization because you have to consider dynamic losses, temperature, pump slip, micro cavitation, suction pressure, etc etc etc when dealing with a fuel pressure.

So the unit of pressure itself is pretty simple. Force per area. But pump efficiency, volume vs pressure capabilities, and head loss are much more complicated.

So, what are you wanting to understand with bottle pressure? Since it is a simple pressure vessel, it doesn't see the same types of problems as a pump. It does still see head loss, but the rest is just a function of pressure differential. Lower pressure, lower flow. Higher pressure, higher flow. It's just like that balloon we talked about earlier. When it's initially full, if you let go of the end, it will flow ALOT of air out, but as it empties and the pressure difference gets smaller, it's not pushing out as much volume.

Hope I made some sense haha

Any questions you're still curious about? Or why you really wanted to know?

20Silverado03

i just want to say thank you for being thorough in your responses, i appreciate that a lot.

-Manny

20Silverado03

so the definition of pressure as resistance to flow still applies right?
or is that definition for pressure head?

im confused

what about a fuel pump with no lines attached? is it still putting out fuel pressure?

MaroonMonsterLS1

Yes. A generalized idea of head is this. Connect your pump to clear hose, and run that hose straight up in the air. The pump will move fluid up that hose until such a point where the pressure head is equal to the pressure differential the pump can supply, then it will maintain at that level. This is why water pressure might be lower in an upstairs shower of your home than in the basement shower.

Fuel pumps see head losses from the fuel filter after it, the lines, any turns, tees, 90's etc. Those losses are usually fairly small, but they're still there.

Boost is a good example of a LARGE increase in head. Boost puts positive pressure on the fuel at the rail...that propagates its way back to the pump, and the pump has to work harder to maintain a pressure differential. Its the same as forcing the water pump in your house to now pump water up to the 15th story of a skyscraper.

also,Yes...without lines, there is still a pressure differential between the inlet and outlet of the pump

Are you just curious about how it all works, or are you trying to achieve a specific goal for your build? If you just want a science lesson, there are people much better at teaching than I am. There are whole YouTube videos, wiki pages, and even textbooks dedicated to explaining in detail what i'm trying to explain in a few short words on a forum. Most of what I've said here is generalized and not a perfect textbook representation of how pumps work, but I hope it gave a good idea of how things are supposed to work.

20Silverado03

so pressure head is resistance to flow AND pressure?

Nitro Dave's Nitrous Outlet

iTrader: (25)

Here at Nitrous Outlet we recommend our customers start off at 950 psi raising bottle pressure properly with a bottle heater wrap around system, billet bottle heater bracket, or using a bottle bath warmer. Torches are very frowned upon when it comes to heating a bottle to raise pressure.

20Silverado03

dave, that wasnt my question

VincesSS

iTrader: (1)

Troll?

MaroonMonsterLS1

What exactly is your question? I think I've done a fairly thurough job of trying to explain fundamentally pressure, pressure head, and given analogies for them as well.

Dave is incredibly knowledgeable and was giving you actual pertinent information to use for your car rather than a science lesson. So, if you wanna ask the same question over and over, and treat people answering you like that, you can head right on over to www.google.com to get your very own science lesson. Or, you can head to www.amazon.com and buy a $250 textbook on fluid dynamics and read it through like I have done.

drive_55_not

iTrader: (1)

When dealing with nitrous, the bottle pressure is just that, the pressure in the bottle, it is not measured as a resistance to flow but how much gas pressure head is in the bottle, and it doesn't correlate to the remaining weight of the liquid n2o in the bottle.

Remember, you want Nitrous held in a liquid state, and the head pressure is pushing liquid nitrous out the of the bottle,, to do that you need to know a couple critical pressure points, 750 and 1070psi, above/below that pressure it'll invert back to a gas

Nitrous is extremely sensitive to temperature, You want to maintain bottle temp as tight as possible to avoid surging. The higher bottle pressure you run, the greater the pressure drop . It'll hit harder on the front-end but fall flat on the back, especially the less nitrous you have in the bottle, the greater the pressure drop.

You can have 960psi bottle pressure with a full 10lb bottle @88'f, and you'll still have 960psi with only 1lb left in the bottle, Obviously when you open the solenoid, you wont have any nitrous flow with a pound left and pressure will drop to nothing.

And as Dave posted, 950psi is a good pressure to run, After a lot of trial and error I've settled on 925 with 82n/36f jets.

.

20Silverado03

so vapor pressure, the pressure of the nitrous vapor on the nitrous liquid,

MaroonMonsterLS1

If you can't wrap your head around a concept as simple as pressure I don't know how much more help anyone on here can give. Either Google a neat youtube video that can dumb it doen, or re-read the answers already given to you.

You haven't asked a question actually pertaining to any car, you just posted repeating questions about science lessons from middle school. Either get productive or End thread.

VincesSS

iTrader: (1)

I'm telling you, he just trolled the **** out of you guys.

20Silverado03

Butts that?