# Increasing CFM in air compressor



## shelly_b (Aug 8, 2012)

I have a 6 gal PC air compressor. I would like to be able to use it with a spray gun for finishing, but I'm pretty sure the CFM is to low (2.6 @90PSI). I really don't want to have to wait on it to fill back up, or listen to it run all the time. I saw in a magazine where someone made a really neat air tool station that included a portable air tank(not compressor) that was used as a resevior. Has anyone done this? If so, would a 10gal reserve tank be sufficient enough to run a spray gun that requires around 4.5CFM at 40PSI? Or do I just need to get a bigger compressor, or spray station?


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## Stephenw (Nov 14, 2011)

The output of the compressor must exceed the demand of the air tool.

You can get bye with a smaller compressor with tools that are used in short cycles such as impact guns, nail guns, and air ratchets. Continuous demand air tools such as air sanders and paint guns require a compressor that is sized for the tool.

You need a larger compressor.

You could also buy an airless spray gun or a spray gun system that includes it's own air source.


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## DIYaholic (Jan 28, 2011)

I have a 30 gallon oilless compressor, however I have not used it for spraying, so take this with a grain of sand. The manual (& chart on compressor) states that *intermittent* spray gun use is possible. So, I would say a ten gallon reserve would not be sufficient.
I'm sure others with actual experience will chime in shortly.


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## fge (Sep 8, 2008)

I don't think the extra tank will be the best answer. The pump on your compressor is not adequate. For 200.00 or a little more an adequate compressor is available.


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## JesseTutt (Aug 15, 2012)

I saw that article; I think it was in Shop Notes. Yes I have a 5 gallon tank that started its life as a portable tank for inflating tires. I converted it so I can connect it as a reserve (additional) tank for the air compressor or I can take it with me to inflate tires or drive a few nails.

Using it as an additional tank reduces how often the air compressor runs. But, it runs longer when it does run. This might give you another minute or two of spraying at full pressure. I agree with StepheW that the best answer is to buy a "spray gun system that includes it's own air source." This is what I did with the Earlex 5000 HVLP system and it has never disappointed me.


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## waho6o9 (May 6, 2011)

http://lumberjocks.com/reviews/3259

Here's a review on the Earlex Spray Station 5500

HTH


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## roman (Sep 28, 2007)

I've seen done, what you ask, many times. You just use your little pancake compressor to fill a larger tank (the bigger the better) and away you go……….works like a charm


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## johnstoneb (Jun 14, 2012)

You need a larger compressor. A larger or more tanks will make it longer before the compressor turns on, but it will not increase the capacity of the compressor to produce air under pressure.


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## davidmw (Feb 9, 2011)

10 gallons is about 1.3 cubic feet, so it would only give you a few seconds of extra use on the spray gun before needing to refill. That said, if your compressor puts out 2.6cfm @ 90 psi 4.5cfm at 40psi might be possible. I would check the specs on the compressor output at lower pressures before buying anything else.

I've used a 60 year old 1cfm @ 90psi compressor for spraying before, and the spray gun worked fine. My spray gun may not require as much air as yours though.


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## shelly_b (Aug 8, 2012)

Thanks guys. I haven't bought a gun yet, but found one on amazon for under $20 with great reviews. If it doesn't work, it's only 20 bucks…


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## Stephenw (Nov 14, 2011)

> David said "That said, if your compressor puts out 2.6cfm @ 90 psi 4.5cfm at 40psi might be possible. I would check the specs on the compressor output at lower pressures before buying anything else."


I think her compressor puts out 3.5 cfm at 40 psi. It is my experience that the cfm numbers on compressor spec sheets are a little higher than what the compressors can actually produce. The air tools also seem to use more air than the spec sheets claim.


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## CharlieM1958 (Nov 7, 2006)

I have to agree with those who are saying the extra tank is not going to help much.

The key is what you plan on spraying. For small projects like a box, or an end table, or a single cabinet, your compressor will work just fine. But if you plan on spraying an entire set of kitchen cabinets at one time, you need a bigger compressor or a self-contained HVLP unit.


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## shawnmasterson (Jan 24, 2013)

what you are referring to is called a "PIG" these are use in industrial settings. it is a 30 gallon tank with a supply line in and feeds out the sides. usually red in color and looks like a momma pig with babies on the side. they are set up when the compressor is to far away. 
I have a 30 gallon set up in the front of my shop to run my heavy demand tools, grinders and 3/4" impact, but it is fed by a 60 gal two stage compressor with a 3/4"line. In your situation a 30 would work for spraying but only in short burst. also it would take forever to fill up, and this will severely shorten the life of your compressor because they are designed to cycle, limiting the heat build up on the head. an oil type my last longer, but still wear faster.
your best bet is to go bigger. something like this would serve you just fine
http://www.ruralking.com/industrial-air-60-gallon-oil-lube-stationary-air-compressor-135-psi-c3706056.html

also the HF spray guns work great and can usually be had for $9.99 on sale 
good luck


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## JoeinGa (Nov 26, 2012)

I did exactly what you're asking … BUT… I had a small (2hp, 30gal) compressor to start with and I had a chance to get a bigger motor and pump (which I jumped on as it was free). Then I needed more VOLUME so I could paint bigger things (like my truck) so I got (again free) another 30gal tank and daisey-chained it to my existing unit.

The thing is, my 5hp motor/pump unit *WILL *supply the added capacity to my system. Your small pump/motor *wont *do what you want it to do. Here's mine before,









.

And after ..
.


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## cosmicturner (Feb 7, 2009)

I am by no means an expert but dot you just match your spray gun to the output of your compressor? You just can't spray the same volume…
Nice set up Joe hope that bad boy accumulator is attached real good.


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## Ken90712 (Sep 2, 2009)

Funny thing about air compressors, I have a good sized on in my shop as I plumed it for both the garage and woodshop with copper piping. I have a buddy with a machine shop who seems to never run out of air. When I looked at his comp, his tank was smaller than mine which surprised me. When I looked at the motor is was a 5hp much stronger than mine so when it kicked on it filled up the tank quickly & recovered quicker with no noticeable lag. Just food for thought. Good luck.

I have the Earlex 5500 and love that as well.


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## shelly_b (Aug 8, 2012)

Joe-thats a great set up. If I use what I have it would be a miniature version of yours lol. I have been looking at the 30gal CF from HF. It's only like $200…but I don't want to get it unless I absolutely have to.


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## shawnmasterson (Jan 24, 2013)

mine is very similar to joe's, but I put the tank in the opposite corner of the shop so I had an on demand supply at both ends it works great if your comp can handle it, and it keeps hose off the floor. on a side note to those who don't know you can use pex tubing on pressures up to 140 psi depending on the brand. mine is plumed with 3/4 pex from the pig to the comp. it does leak down slowly but I always turn off the valve at the comp when not in use. it is way more cost effective and easier to run/modify.


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## JoeinGa (Nov 26, 2012)

Thanks for the nice comments. I dont really have any "EXTRA" floorspace, so I wanted to get the additional tank somewhere out of the way. UP was my best choice. I took a few measurements and bolted some sturdy chains to the rafter.

I stripped everything off the tank that I could to get the weight as light as possible. Then I leaned my 10' stepladder against the wall and just muscled that tank up the "ramp". Then while holding it up there with my shoulder, I reached under and brought the chains around to the bolts. WAA LAA …. doubled my capacity.

I ran my hoses up along the rafters to keep them off the floor. I put drops in 3 places where I use it the most.


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## shelly_b (Aug 8, 2012)

jonathan- the extra tank doesnt change the pressure, just the capacity. If your tank holds more air, then it has to fill up less often, since you don't run out of air as fast.


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## shelly_b (Aug 8, 2012)

ohhh ok. sorry! I miss understood your question


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## shelly_b (Aug 8, 2012)

The way I understand is it's just for convenience, so he doesn't have a hose stretched across the garage since he has a tank at both ends. I may be wrong though…


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## fge (Sep 8, 2008)

The extra tank adds more capacity to hold air so the motor would have to turn on less, but the motor would stay on longer to fill the extra capacity. Also, it is your pump and motor that provides your cfm spec, not extra tank space. Chances are, if your compressor is too small to run a spray gun, adding a tank will not change that fact. The compressor will just continue to run non stop trying to keep up.

Online you can purchase a decent Rol-air compressor, twin tank, 4.5 gallon, 2 hp oil lubed pump, around 5 cfm at 90 psi. And you would get it for around 240.00 and likely free shipping if you look around. So for just a few more dollars, a much higher quality compressor would be in your shop then what is offered by harbor frieght.

I disagree with the idea of going with an Earlex for 300.00 or more. One can buy a good quality Rol-air that will last a lifetime if maintained and not abused, a good quality cup gun can be had from woodcraft for about 40.00. And the air compressor can be used for nail guns, airing up tires and toys, etc…


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## shawnmasterson (Jan 24, 2013)

~Jonathan~ I have tools like my 3/4" impact It uses a lot of air (very high cfm) and the longer the hose gets the larger diameter it needs to be to flow enough volume to run properly. if you put a framing gun on a 1/4" hose @ 50' long it will fire the nail, but make that same hose 200' now there isn't enough volume to fire that nail. lets say you set a pig at 150' then the pig will accumulate enough volume to work without a larger hose. by setting the tank in front of the garage it allows me to put the comp in the back corner of the shop so if I hook up in the front or back I have the same volume of air to run anything I want. also the impact requires a 3/4" line to run right ($$$$$$$) by hooking to the pig it saves me 30' of extra 3/4" hose. old compressor tanks work great, they are thin and you can weld a bung any where you need to tap in. just drill a hole with a hole saw and weld in a fitting. (don't try it if you can't weld)


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## shawnmasterson (Jan 24, 2013)

not yet but you may if you have it. I am a believer In go big or go home. I started with a 30 gal C-man oil less I rebuilt the head 3 times before the motor gave up (8 years). that was when I decided to go big. I helped my neighbor build a 260gal dual pump unit. the pumps were from a tire service truck it took 10 HP to power it, why cause he could. after setting it up we discovered he could leave the 1/2" drain open and it would cycle on and off. it is insane.


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## fge (Sep 8, 2008)

Nice looking air compressor Jonathon.


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## shawnmasterson (Jan 24, 2013)

why put it up in the air? we did that with my neighbors. is there a reason or just cause


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## Grandpa (Jan 28, 2011)

The extra tank is a reserve and when the reserve air is gone the compressor can't keep up. If the gun uses more air than the compressor can produce then it uses the reserve. How fast the reserve is depleted would depend the difference between the supply from the pump and the demands of the gun. If you were painting something large you would end up with dead places and dissappointment. Small boxes or something of that nature might work but why would we shoot small projects? Save toward a large compressor. 
Shawn is correct when he talks about longer hoses etc. You can overcome some of that by running high pressure out near the end of the hose then set a regulator. They make some with a belt clip.


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## SRRieman (May 31, 2012)

Shelly, there is a couple of things you need to understand and not overlook. Most people will sit here and say that volume will not increase your cfm and they are wrong. The volume will increase your cfm. However, it will not increase the running cfm. Think of it this way. If you had two air compressors, both using the same exact motor, but one having a larger tank than the other. The compressor with the larger tank would have a greater cfm rating, but the running cfm specs would be the same. Whether or not the system would work for you depends primarily on how you intend to use it, that is how much you intend on spraying. What I would do is give your current compressor a trial run. First try spraying with what you have, regulated at 40 psi of course. You can do this by spraying water through the gun and timing yourself or by actually spraying the project you intend on finishing. This will give you a better idea of what you will need. The larger the capacity, the greater amount of time you will have to spray. It's really much more simple than most people make it out to be. Regardless, I wouldn't go out and buy a new compressor. It's more than likely not needed if all you plan on using it for is finishing. And one more thing, a small fan directed towards your compressor motor will work wonders on overheating. Most compressors have one already but they don't barely work at all. A real fan, with good flow, will keep the temps down, and will do so a lot!

Good Luck!


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