You have surely seen that your air compressor has a CFM rating and the tools you use also require a certain CFM level to operate. Different tools require different CFM rating.
Sometimes you need increased CFM. Two of a good example is when you use your air compressor for impact wrench and spray painting.
So, how to increase CFM on air compressor? I am here to answer this question for you. But if you are not already familiar or clear about what CFM is, then here is a quick brief for you.
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What Does CFM Mean In Air Compressors?
CFM or Cubic Feet per Minute is a very important term for an air compressor. In a simple term, CFM is the flow rate of the volume of air that comes out of an air compressor.
If a compressor has a rating of 8 CFM, this means 8 cubic feet of air will come out in one minute, from that compressor.
CFM is directly connected to the application of the compressor. For different air tools you need different CFM, and so you have to get an air compressor according to that CFM level.
How to Increase CFM on Air Compressor
Usually, an air compressor is built with a specific CFM rating for a specific pressure (Like, 2.6 CFM at 90 PSI).
However, I found some ways that you can follow to make your compressor a high CFM compressor. These are –
Method 1: Decreasing the Pressure to Increase CFM
A compressor first takes air inside. Then it builds pressure in the tank. This pressure then helps the air to go out at a certain rate which we are referring to as CFM.
Every air compressor has a certain power level. This power depends on the pressure and the CFM. Mathematically speaking, Power = Pressure x (Volume/Time). Here (Volume/Time) is CFM. To keep this constant power, if you increase the CFM you have to lower down the pressure.
However, you cannot operate an air compressor beyond its power limit. So if you can build less pressure in the tank, then the CFM of your compressor will increase. And to do so, you need to dial down the regulator.
When you dial the regulator down, air flows into the tank slowly and builds a lower pressure inside. This lower pressure then allows you to have a higher CFM.
An example will clear this out for you. Let’s say you have a compressor with a rating of 5 CFM at 90 PSI. What does this mean? It means if the pressure reaches to 90 PSI then the compressor will provide an air output volume of 5 CFM.
Now, when you decrease the pressure from 90 PSI there will be an air output of more than 5 CFM. So this is one way to increase CFM on an air compressor.
If you follow this method, you can only reach a certain limit. But this is safe for your compressor and won’t damage the compressor anyhow.
Method 2: Connecting Two Compressors to Increase CFM
The previous method won’t be able to provide CFM higher than the maximum limit of your compressor. What if your compressor has a maximum limit of 5 CFM but you need more than that.
In this case, there is another method that you can follow. Here you will be connecting two compressors for more CFM. How does this work? Well, if you connect two compressors having 5 CFM and 3 CFM, then you can get 8 CFM at once.
So, how can you connect the two compressors? It’s very simple. Just follow these steps –
- Take two compressors and connect the tank of both compressors with two different hoses.
- Then take another hose, and connect the two hose with the third one.
- The third hose should have three holes so that two of the holes can be used as inputs and the third hole can be used as an output.
- Now connect the output of the third hose with your tool and you are done.
You can use this method if you need a higher CFM than your compressor can provide. But there is a thing you should keep in mind.
If you already have two compressors, and you need a higher CFM, then you can connect them. But what if you don’t have two compressors? Will you buy another one with a low CFM and connect them?
It depends on what type of works you do with your compressor. If you only do works that require high CFM then it is better that you buy a high CFM air compressor.
But if you have to do works with low CFM then having two compressors is a great idea.
FAQ Related to CFM of an Air Compressor
How do I know what CFM my air compressor is?
When you buy an air compressor, the CFM should be written in the manual. But if you forget the CFM level and lose the manual for some reason, here is a practical way to calculate CFM.
- First, find the volume of the tank in gallons.
- Divide the Volume by 7.48 and you will get the volume (V) in cubic foot (1 cubic foot = 7.48 gallons).
- Now empty the tank and refill again.
- While refilling start noting the time shown in the gauge. It is shown as PSI (pounds per square inch)
- Here take the time of kick in and kick out of the compressor and calculate the difference (i.e. if kick in time is 70 PSI and kick out time is 90 PSI, then the difference is 20 PSI).
- Now divide this value by 14.7 and you will have pressure (P) in ATM.
- Now simply multiply P with V and divide by 60 to get CFM (CFM = P*V/60)
How much CFM do I need for air tools?
Different air tools require a different level of CFM to operate. Like, a general ½” impact wrench requires about 5 CFM to operate. On the other hand, a framing nailer requires 2.2 CFM whereas tools like a pneumatic stapler require only 0.3 CFM to run.
What is a good CFM rating for an air compressor?
For an air compressor, 4 CFM at 100 PSI is a good rating. But there are a lot of different types and kinds of air compressors and they have different CFM ratings according to their application.
Low powered Compressors generally provide a maximum of 0.5 CFM and high powered ones can provide 8 to 10 CFM.
What’s the difference between CFM and SCFM?
CFM or cubic feet per minute indicates the volume of air that is flowing out of an air compressor. It shows how much cubic feet of air is blowing out in a minute. But there is not standard pressure or temperature set for CFM.
However, for SCFM or Standard Cubic Feet per Minute, there is a standard pressure and temperature set. Based on that standard, SCFM is measured and so it can vary from place to place.
What is the difference between PSI and CFM?
CFM or Cubic Feet per Minute is a unit that shows how much air is flowing out per minute. This is used to measure the volume.
PSI stands for Pounds per Square Inch which indicates the pressure level of air in a compressor.
A Final Tip
My final advice for you would be to match the CFM rating with your tool and get a compressor accordingly so that you don’t have to go through the troubles of increasing the CFM.
But if you do need to increase, following my methods will surely come handy for you. Hopefully, you will no longer have any doubt about how to increase CFM on air compressor, from now on.