# Does CFM of a compressor increase if pressure is reduced?

In product description of the compressor, CFM is mentioned to be 185 Liters per Minute. And pressure is mentioned to be 115 PSI.

Lets say, If I only need 30 PSI for my spray gun but CFM required by the gun is 200 L/M. Would above mentioned compressor be able to provide required air flow?

Compressor has a 2 HP motor.

Absolutely Yes, this is simple physics the air is not requiring as high of pressure the throughout increases. Most air compressors rate there pump rates around 50 psi, 90 psi and the max psi. Even my cheap little pancake oil less has a dual rating of 3/6 scfm I don’t know for sure the exact number but was able to find the formula on line. Just Google the ideal gas laws and there are many examples of this formula. PxV = nRT ; where P = pressure , V = Volume, T = Temperature, n is the amount of gas present and R is a constant depending on the units used for the other variables.

There is a practical limit my 5000 psi compressor is only rated at 6scfm the volume increases as I reduce the pressure but because of the volume of the pistons and motor speed it will not jump as high as my little pancake compressor.

Does CFM of a compressor increase if pressure is reduced?

No. If pressure is reduced, CFM is reduced. CFM is just a measure of pressure over time.

Would above mentioned compressor be able to provide required air flow?

Maybe.

• Yes; If the compressor has a chart showing the throughput at a range of pressures, and if the compressor is capable of providing 200 LPM at a higher pressure, then yes the compressor may be adequate - you would next need to calculate whether the storage capacity would allow for delivery of that volume for a practically useful duration. You will have to decide what a "useful duration" would be - do you need 30 seconds of continuous spray or 300 seconds? Additionally, the higher the pressure on an air-powered sprayer and the greater the cycle frequency, the greater the volume of moisture. That is to say, even if you can eke out the required performance from a given air compressor, the moisture content in the air might be incompatible with the product you're trying to deliver.
• Yes, possibly; If the performance specs are achievable, but the regulator is limiting, there are ways to modify a compressor's components to achieve greater throughput, but that would be a whole other post and line of questions. Not all compressors can be safely modified even if the technical specs are there.
• No; if the 185 LPM is the max output and/or it isn't feasible to modify the equipment to increase the max output.

Good luck @ishaan karnik

If it is for the compressor then no, the CFM is based on the delivery of the compressor .

If however there is a storage tank then changing the outlet pressure to lower than the storage pressure will make a difference to the CFM.

• hmmmm generally compressors are rated at a certain number of CFM (or L/M across the pond) at a certain PSI. At a much lower PSI, it's reasonable to expect a higher CFM (L/M) that might need the OP's needs. It'll be close. Worst that could happen is he might have to pause spraying for a few seconds for the compressor to "catch up" ...usually not a problem...but if spraying lacquer and trying to keep a "wet edge", it could be. Commented Feb 4, 2021 at 11:06
• @GeorgeAnderson are you talking about just the compressor part or when it is combined with a receiver or a hplv sprayer which can inject paint under the skin? Commented Feb 4, 2021 at 11:25
• @SolarMike I'm not clear on how the tank makes a difference here. The CFM rating is always given at a specific PSI and even if it's just a compress with a hose (effectively a small storage tank) you will get more CFM at a lower pressure than at a higher one. Commented Feb 4, 2021 at 14:53
• @jwh20 so take the demand from a compressor and reservoir, if the demand is less than compressor drlivery then the reservoir never gets emptied but if the demand exceeds the compressor drlivery capacity then the reservoir will be emptied and then the compressor cannot meet the demand by itself. Just down to max flow rates and vol delivery... And even trucks can run out of air under braking in some situations - but good drivers are aware of that... Commented Feb 4, 2021 at 15:09
• Got to down vote this is simple and most air compressors have multiple flow ratings. The change is the pressure not the tank or speed but how much compression is required. Lower compression = higher flow. Commented Feb 4, 2021 at 15:30