1/4 inch airbrake line for fuel pressure gauge

[015point9]

Anybody have a good memory?  Someone posted a pic of a brake airline they used for their low fuel pressure gauge.  I can't find it now.  The pic had name printed on the hose.  I would like to track some down.  Anybody remember the post or know what line to use? 

   

At my NAPA I asked for 1/4 inch airbrake line and they wanted to sell me what's listed below. After looking up what they sell I don't want to use it.  It's not even brake line and I've hit the "bold" to show where I think it is lacking.  Or if anybody's  used this, is it good enough?

 

Maybe just me but I was thinking there must be something better.

 

Thanks for any response.

 

https://www.haldex.com/en/North-America/search/?q=d1060401

 

 

Reinforced Nylon Tubing

Part no. D1060401

Air Dryer/Air Line > Air Line Tubing > Nylon Tubing (Bulk) > Reinforced Nylon Tubing > D1060401

 

Reinforced Nylon Tubing

• Meets Type B SAE J844 Specifications and FMVSS No. 106 Regulations
• Temperature Range: -40° F to +200° F
• Maximum Working Pressure: 150 PSI
• Not made for fuel

 

 

[Mopar1973Man]

1/8" air brake line of any brand name will work. Don't use 1/4" too big and will allow pulses travel farther to the gauge. The 1/8" air brake line will help in snubbing the pulse out some.

[BBHD]

I also used the 1/8" air brake line from Napa for my fuel pressure gauge routing.  It's holding up great now almost a year later and 24k 

[Ilikeoldfords]

1/8" would be perfect for your gauge. One question I have is about the fuel rating. Is anyone concerned that it specifies NOT FOR FUEL?? When I ran my gauges I made sure to get line made for oil and fuel use. If it were me personally I wouldnt want to risk that line failing in my cab or over the hot engine. Just a thought.

[015point9]

Op here....Sorry folks...I mis-typed.  1/8 inch is what I should of typed.

 

Mopar man...I'm a new member...Couldn't get the "donate page" to work about week ago.  And want to chip in something and have couple other questions. Time permitting at your end please PM me when convenient.  

 

Thanks

[KATOOM]

I've used both 1/8 and 1/4 inch air-brake line for fuel pressure gauges.  And I prefer the larger of the two because of these reasons:  Its less likely to kink, more mass to prevent unwanted rubbing through on other objects, 1/4 has better sealing fittings over that of the tiny 1/8 compression, its much easier to bleed air out of 1/4, its easier to plumb through and around things, and.....the hydrodynamic pulses are less.

 

Yes, I've argued this before but it seems to continually go unheard for some unknown reason too.  Larger diameter line will actually reduce the pulses traveling through the lines due to the larger volume of the static fuel inside over that of tiny little diameter lines.  Remember, the gauge line is "static".....  For the pulses to travel through larger lines takes more energy and force, thus they weaken faster.  And the change in diameter is greater through the snubber.  But hey, I'm obviously talking in some strong wind when this topic comes about.....

[TFaoro]

I agree with @KATOOM. Larger line will actually dampen the pulses more than a tiny line. I like my electronic one though.... No fuel in the cab for me  

[rancherman]

Friction boys...FRICTION, (Mike called it  'snubbing')    is  what  'dampens'.    Small lines have  a lot more friction  than larger ones.

 

PLUS,   the smaller lines have far less  inertia that  larger lines.  I should say the fluid  within the line has less inertia..  both from it's mass,  and  the  friction  factor.

[KATOOM]

Friction plays ZERO part in this equation.  Fluid friction is something you calculate when you're figuring how fast fluid can flow through a specific size line before volume and pressure are affected, and the fluid abrasively deteriorates the wall material.

 

Snubbing is whats happening when the fuel flows through a larger line through a smaller hole and then back to larger.  Thats not friction.

 

Instead we're talking around 15 psi of pressure here, and hardly any fuel movement at that.  A smaller diameter line will move more pressure faster and harder as there's less mass/volume to move within.  Physics.  Thus why the fuel injection lines on this engine are necessary to be the smaller diameter they are, and why most high pressure components/tools have smaller diameter lines.

Edited September 26, 2016 by KATOOM

[BBHD]

I was concerned about abrasions on my 1/8" line so it's sleaved from the firewall to my guage in 1/4" line. 

[dripley]

[TFaoro]

3 hours ago, rancherman said:

Friction boys...FRICTION, (Mike called it  'snubbing')    is  what  'dampens'.    Small lines have  a lot more friction  than larger ones.

 

PLUS,   the smaller lines have far less  inertia that  larger lines.  I should say the fluid  within the line has less inertia..  both from it's mass,  and  the  friction  factor.

Technically, a larger line would have more friction because it has a larger surface area under the same pressure. We don't use friction here though because the fluid isn't flowing at the walls of the hose, only in the center  

 

Inertia does not play a role here because the fluid isn't actually flowing.

 

F=ma or a=F/m.... Acceleration is what we're worried about here. If the fluid accelerates into the gauge, then that's where problems occur. The F remains constant as the pulses from the VP44 hit it, so the only thing we can change here is m. A larger line carries more mass, and thus damps more. 

 

Think of it this way, if you have a 55 gallon drum of water and put a pressure sender on it then add 20psi and pulse it 5psi either way through a needle, you won't see the gauge bounce like crazy. If you do the same with a 1/8in line, you will see the gauge bounce much more. 

 

The other way to cut the pulses is to have a snubber, which cuts down the size of the orifice allowing fuel in, thus the needle used in the example above. 

[Dieselfuture]

You guys over thinking it, use a niddel valve and get your pulse frome vp to minimum and if you get a leak jump out and shut off the valve. I used 1/8" line and quick connect fittings, and ran the line through an old 1/2" fuel line through firewall and it fits perfect over quick connect that's on the guage, so if my fitting does leak all of the fuel will dump out 2" pass the firewall and dripping on the ground. Plus it's like a conduit for the tiny plastic line, less chances for it to get cut.  

Edited September 27, 2016 by Dieselfuture

[KATOOM]

55 minutes ago, TFaoro said:

Technically, a larger line would have more friction because it has a larger surface area under the same pressure. We don't use friction here though because the fluid isn't flowing at the walls of the hose, only in the center  

 

Inertia does not play a role here because the fluid isn't actually flowing.

 

F=ma or a=F/m.... Acceleration is what we're worried about here. If the fluid accelerates into the gauge, then that's where problems occur. The F remains constant as the pulses from the VP44 hit it, so the only thing we can change here is m. A larger line carries more mass, and thus damps more. 

 

Think of it this way, if you have a 55 gallon drum of water and put a pressure sender on it then add 20psi and pulse it 5psi either way through a needle, you won't see the gauge bounce like crazy. If you do the same with a 1/8in line, you will see the gauge bounce much more. 

 

The other way to cut the pulses is to have a snubber, which cuts down the size of the orifice allowing fuel in, thus the needle used in the example above. 

 

Precisely.....

But just to clarify for everyone else, the snubber is working based on the Bernoulli principle, not just because the hole is small.

[TFaoro]

1 hour ago, Dieselfuture said:

You guys over thinking it, use a niddel valve and get your pulse frome vp to minimum and if you get a leak jump out and shut off the valve. I used 1/8" line and quick connect fittings, and ran the line through an old 1/2" fuel line through firewall and it fits perfect over quick connect that's on the guage, so if my fitting does leak all of the fuel will dump out 2" pass the firewall and dripping on the ground. Plus it's like a conduit for the tiny plastic line, less chances for it to get cut.  

Where do you think that "answer" came from? Engineering my friend, and I'm an engineer. That's why I like to explain exactly how it works, not just it works because everyone does it  

 

1 hour ago, KATOOM said:

 

Precisely.....

But just to clarify for everyone else, the snubber is working based on the Bernoulli principle, not just because the hole is small.

100% correct. Guess I should have explained that too! As the velocity increases (going through the snubber) the pressure on the other side is decreased, and thus the "hammering" effect is decreased. 

Edited September 27, 2016 by TFaoro

[rancherman]

 

    just to clarify,  can you  post a pic of this 'Bernoulli's  device'  and how   you have it installed?   

 

 

 

[notlimah]

Sounds familiar eh @KATOOM!? 

 

[CSM]

25 minutes ago, rancherman said:

 

    just to clarify,  can you  post a pic of this 'Bernoulli's  device'  and how   you have it installed?   

 

 

 

 

You dont just ask to look under a wizards friggin hat, Sir.  

[TFaoro]

31 minutes ago, rancherman said:

 

    just to clarify,  can you  post a pic of this 'Bernoulli's  device'  and how   you have it installed?   

 

 

 

Here you are! It's a principle though ;)

[rancherman]

ok.  now  please  try  to explain how  Sir  Bernoulli's  Principle   works    in a  dead end  line.    this  should be interesting.   

Wizards hat?  cripes,  the man has been dead  for 200 years.  I think it's not the secret you think it is.

And yes, as a  matter of fact,  this  DOES  seem very damn familiar. 

 

As far as   pressure (head loss)  loss  due to frictional forces.   Diameter is  most certainly a factor.   Not as much as  I originally  thought however.

 hf = f (L/D) x (v^2/2g)

where:
hf = head loss (m)
f = friction factor
L = length of pipe work (m)
d = inner diameter of pipe work (m)
v = velocity of fluid (m/s)
g = acceleration due to gravity (m/s²)  

If  diameter was not a factor,  it  wouldn't be included  in this    formula.

1 hour ago, TFaoro said:

Where do you think that "answer" came from? Engineering my friend, and I'm an engineer. That's why I like to explain exactly how it works, not just it works because everyone does it  

 

100% correct. Guess I should have explained that too! As the velocity increases (going through the snubber) the pressure on the other side is decreased, and thus the "hammering" effect is decreased. 

true,  any FLOW immediately  in the  THROAT  area  is   by definition  reduced in pressure.     That's  a  given.     But every example of  Bernoulli's Principle  shows  the pressure  goes  right back up  downstream of the  throat area   

Gauges  are most  definitely  'downstream' of this  area.