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Discussion Starter · #1 ·
Hi all,

I have an Astro Evo 1.4mm spray gun. I am using 3/8" I.D air hose and I can't set the psi right...it always read at 8 psi with trigger pull..plus I turned the regulator all the way up...the gun stated air in 16-19 psi

I read the spec and it said Air Inlet I.D is 1/4"..

My question is does the air hose I.D matter?

My A.C is 8.6cfm @ 90 5.5hp 30gal
 

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Brian Martin,Freelance adviser
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No, NO, you don't want to downsize! You want at big a hose as you can haul around. You want as big of pipe, and as big of hose as you can get away with.

A quarter inch hose is WAY too small for any HVLP gun. You need VOLUME (the V in HVLP) and the larger hose gives you that.

Brian
 

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Discussion Starter · #6 ·
MARTINSR said:
No, NO, you don't want to downsize! You want at big a hose as you can haul around. You want as big of pipe, and as big of hose as you can get away with.

A quarter inch hose is WAY too small for any HVLP gun. You need VOLUME (the V in HVLP) and the larger hose gives you that.

Brian

it's not the HVLP. it is an Astro Evo LVLP
 

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The size of your air hose is not the problem. All my guns have 1/4 inch inlets and all my hoses are 3/8's.

You bought a made in Japan spray gun and probably purchased their regulator. The regulator is your problem.
 

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Discussion Starter · #9 ·
cjperotti said:
The size of your air hose is not the problem. All my guns have 1/4 inch inlets and all my hoses are 3/8's.

You bought a made in Japan spray gun and probably purchased their regulator. The regulator is your problem.
As you said I can't use regulator from HF or other brand...I have to buy same brand as the gun?
 

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Discussion Starter · #10 ·
AntnyL said:
What's the cfm rating of your gun with the trigger pulled? Does it exceed the cfm capacity of your compressor?
Spec data said 16-19psi. 9cfm

I have Digital Reg and with the trigger pulled it reads only 8-9 psi with 3/8" air hose

So I went to change air hose to 1/4" and it jump to 20psi
 

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What in the world are you talking about? If you want a decent regulator for your gun go over to Lowes and purchase their 1/4 inch inlet regulator for $14.95 and mount it on your gun. I have one on my primer gun and swear it preforms as well as my Devilbiss regulator on my spray gun.
 

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Do you actually have 3/8" ALL the way from the regulated source? It won't matter if you have a 1" hose if it is choked down by a small or obstructed fitting somewhere between the regulated air supply and the gun regulator. I have even seen Chinese made fittings that were so poorly made and rough inside that even though they may have been for 3/8" they would not flow the equivalent of a 1/4" fitting. Make sure you don't have a restriction somewhere in the system, it sounds as if you do.
 

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Discussion Starter · #13 ·
oldred said:
Do you actually have 3/8" ALL the way from the regulated source? It won't matter if you have a 1" hose if it is choked down by a small or obstructed fitting somewhere between the regulated air supply and the gun regulator. I have even seen Chinese made fittings that were so poorly made and rough inside that even though they may have been for 3/8" they would not flow the equivalent of a 1/4" fitting. Make sure you don't have a restriction somewhere in the system, it sounds as if you do.
I have 1/4" fitting and 3/8" air hose...it made by craftsman I believed...

When I switched to 1/4" air hose my guns work very good...so far i have test them and it works very well...I will try to shoot some clear tomorrow to see if i still get milky look...I always get milky look on clear..it seems like it lacked of air..
 

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Discussion Starter · #14 ·
cjperotti said:
What in the world are you talking about? If you want a decent regulator for your gun go over to Lowes and purchase their 1/4 inch inlet regulator for $14.95 and mount it on your gun. I have one on my primer gun and swear it preforms as well as my Devilbiss regulator on my spray gun.

Ok I bought a digital one from H.F..when I was using 3/8" it will never get to 20psi @ the reg..but then I switched to 1/4" I get 20psi with trigger pulled..
 

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For reference.

The 3/8" hole is twice the area of a 1/4" hole.

The hose will cause resistance. A long hose with 1/4" couplers will cause a significant pressure (flow rate) drop. This is a two fold problem as the 1/4" couplers can flow less air and there is friction loss from the long hose.

My experience with my HVLP guns all Devilbiss (mid range gun and a GFG) was a pressure loss when I was using the 1/4". The bumper demon does not need as much air. This gave me very inconsistent results as I would have the pressure and flow for testing and the start. Once the static pressure in the hose dropped the gun did not spray as well since the 1/4" fittings could not flow enough air to supply the gun properly.

Since switching over to all 3/8 couplers I have found all my other tools are more consistent.

Keep in mind I only have 3/8" hose, that is the most common hose and is likely what you already have.

I have also found that the gun regulators may not be able to supply enough flow rate to work on a big gun. Only the better regulators can give you the flow rate. The common ones you find work well on the small guns such as the Bumper Demon.
 

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What type of compressor do you use, what is the airflow stated on the compressor. With a small compressor it will not put out the volume needed to fill a larger diameter hose, that may be why you're getting a higher reading with the 1/4in hose.
 

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The Penny Pincher
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I switched to 3/8" couplers and it made a huge difference.
A larger hose than 3/8" made no difference.
It's the couplers that are the bottle-neck.
Look inside a 1/4" female quick disconnect and you'll see the actual
passage for air is choked down more than half.
the hole is only about 1/8" dia.
That's the restriction, switching to a 3/8" disconnect doubles
that opening. Still not as big as a 3/8" hose but more than twice
the volume of air can pass by than a 1/4" disconnect.



I made this and adjust my air at the wall until I get the right amount
at the gun, then I remove it.
Most regulators restrict air flow,
This is truely what I get when set.
 

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acquadigio79 said:
When I switched to 1/4" air hose my guns work very good....

So are you saying that your system works better with the 1/4" hose? There is absolutely no way the 1/4" hose would work as good as a PROPERLY working 3/8" hose. Either you have changed some of the fittings along with the hose and eliminated the obstruction or that 3/8" hose was plugged up somewhere along it's length. Like Shine said 1/4" hose is for airbrushes you need that 3/8" hose along with the proper high flow fittings.
 
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