What Size Air Compressor Do I Need To Paint A Car?

If you are not experienced in auto painting, you may need to perform a little research on the best compressor to use first, because what size air compressor you need is not a straightforward answer.

The air pressure, tank capacity, airflow, and other aspects are all part of the answer when consider which size air compressor for auto painting you’ll need. Please read on for our comprehensive guide, or for more information on the right size air compressor for any job, please see our huge guide What Size Air Compressor Do I Need? You may also be interested in other guides in the series such as What Size Air Compressor Do I Need To Fill Car Tires and What Size Air Compressor Do I Need For An Impact Wrench?

Selecting the Right Size Air Compressor for Painting a car

Does the tank size matter when it comes to painting a car? 

Yes, the tank size matters a lot when painting a car. The tank is the reservoir for pressurized air that you will need during periods of peak air demand. You will find paint gun types that are extremely demanding so you will need a good supplement.

The larger the tank, the higher the amount of air it can carry, and the easier it is for you to use demanding paint sprayers. If you want to spray your car at a go, you would want to go for a larger tank. A small tank is undesirable because it not only will do an uneven job, but also probably not finish the job.

What CFM rating do you need to paint a car? 

It is equally important to consider the CFM (Cubic Feet per Minute) rating of a compressor for spray painting. CFM indicates the amount of air the device is capable of delivering per minute. A high CFM rating is recommendable because it helps you have more air pressure, and therefore are able to paint thoroughly in a single stroke. Poor finishing is associated with low CFM rating. Therefore, if you are after the best results from your painting efforts, choose an air compressor with high CFM rating.

A rating of about 18cfm is usually applicable for big car painting jobs. It gives uniform and fast results. Casual painting jobs and retouches can work with a lower rating, say 4cfm.

What PSI do I need to paint a car?

PSI rating is the common definition of air pressure in an air compressor. Ideally, a compressor for spray painting should have a large capacity and at least a medium pressure rating. You want to achieve the best results without creating excessive pressure. The best air compressors for painting car are able to deliver excellent results with minimal pressure.

What does PSI to the cap mean?

The air cap is a crucial factor of the spray gun because it determines the speed of painting as well as the quality of the finish. This component comes into focus when painting during the pressure measurements.

Some spray guns come with air pressure maintenance from the manufacturer and they work just fine. However, the manufacturer cannot account for all the variables – length of air hose, amount of thinner included, thickness of coat of paint, temperature changes and so forth. Moreover, the manufacturers often don’t tell where they took the pressures at. It could be PSI to the cap, regulator, or the inlet of the spray gun.

Since you want to adjust the PSI at the cap, measurement at this location becomes necessary. Instead of buying a special cap, you can use the regulator in a few steps to determine the PSI at the cap.

What size tank do I need? 

The actual tank capacity is a big part of the answer to what size compressor for spray painting as you will need a fairly large volume of air, therefore high capacity air compressors are best for this job. Typically, a unit with at least a 30 gallons air compressor tank is suitable for painting a car. You only need the CFM ratings of the compressor and the painting gun. For the best performance (a situation whereby the compressor doesn’t have to run continuously during the painting process), make sure that the compressor’s maximum output is more than the requirements of the gun.

I found a great video where someone proves you don’t need a huge compressor for auto painting – in fact they used a tiny 6 gallon pancake compressor! Video credit to The Paint Society.

What about duty cycle? 

Some air compressors need to rest for some time during their operation to cool down. This is important for prevention of breakdown and enhancing product life. While this concept is easy to understand, you cannot easily read the value on the air compressor because it is rarely indicated.

The most popular representation of duty cycle is in terms of percentage of period, for instance 10 seconds. However, there are times when it is given as time. When the duty cycle is given as a percentage, it is the ratio of the runtime to the cycle time. If a compressor for auto painting has a 50% duty cycle, then it means that for an operating time of 20 minutes, it runs for 10 minutes and rests for the next 10 minutes.

Does an air compressor for spray painting need a specific amount of horsepower (HP)?

The horsepower rating is also a primary consideration when choosing which size air compressor to you need paint a car. Horsepower refers to the amount of work that the air compressor can deliver.

Typically, air compressor meant for spray painting feature horsepower of utmost 6.5hp and not less than 1.5hp. If your air compressor will draw from a standard electrical outlet, choose a rating of up to 2hp.

It is important to note that usually, different types of air compressors have different HP compressor ratings. For instance, for a diesel-driven air compressor to perform the same amount of work as 5hp electric version, it needs to have a 10hp motor.

This demonstrates the difference in efficiency of the two types of air compressors. The diesel-based air compressor works through combustion while the electric one depends on an external source of power.

Recommended size air compressor based on the type of spray guns 

When considering the best air compressor size for your car painting application, the type of spray gun will also matter a lot. There are two main types of spray guns in the market today namely high volume low-pressure (HVLP) and low volume low pressure (LVLP). Below is a brief review of the types of two spray guns:

Air compressors for HVLP spray guns

With this type of paint gun, you need to have an excellent air compressor to get the best from the tool. Most of guns in this category work at about 50PSI and 20cm, meaning that the tank should at least have 80 gallons capacity.

Air compressors for LVLP spray painters

For these spray guns, the common airflow rating is about 5cfm and pressure of between 10 and 25PSI. With these characteristics, it is clear that these tools can pair with more air compressors than HVLP spray painters can. Therefore, you want to go for these ones if you are looking for a convenient spray painting process.

Can you paint a car with a portable air compressor? 

Yes, you can paint a car with a portable air compressor, provided the compressor is reliable enough for this demanding job. The BOSTITCH Pancake Air Compressor, Oil-Free, 6 Gallon, 150 PSI (BTFP02012) is a perfect example of a portable unit that does the car painting job well. This machine is equipped with a powerful motor that starts effortlessly in all type of weather.

With its 150 PSI maximum, this air compressor offers more than enough air pressure for the painting task. Its airflow at 90PSI is 2.6cfm, which is also suitable for a professional touch.

A 6-gallon tank offers the adequate storage that ensures that the job runs smoothly. If you order the premium kit of this product, you will receive a 50 foot 1/4 inch air hose. Also in this air compressor for painting are couplers and a flow regulator.

What is the smallest air compressor to paint a car? 

The BOSTITCH Pancake Air Compressor is small, but there are even smaller air compressors that can still be enough paint a car. The smallest size compressor you should be considering should be rated at least 14PSI. Note that it will mostly be usable in applying the base coat, but not the finishing paint job. You can use it to paint car parts, but extensive surfaces will take a long time to complete.

Conclusion

You will never regret buying an air compressor for painting cars, as in addition to being great for spray painting, an air compressor can inflate tires and support many other power air tools.

By understanding the technology behind air compressors and choosing to own one of these machines for your DIY projects, you are avoiding the trouble of having to find an auto shop every time you need to paint the car.