Setting up my personal garage with a proper air compressor and set up for painting my project car and potential future projects, I have done alot of homework and checked numerous avenues for inputs. Here is what I learned and consolidate it into one post.
1 – the Compressor – The Compressor size besides the tank (go 60 Gal or bigger) is more about the pump itself. The volume of air the pump produces is what matters. Most 60 Gal compressors on the market I found produce over 11 CFM at 90 PSI, some do more. The HP of the pump does help and will ensure the tank gets filled with the least amount of power needed. The downside of having to go this big on a compressor is you need 220v.
I tried spraying primer on my project car using a 26 Gal 1.5HP compressor rated at 4CFM at 90 (the same as the Concours gun I use) and it ‘applied paint’ but by no means painted the car. The primer, the Contour Poly from Eastwood required a 2.2 fluid tip on the gun. Because the air flow was not the best it came out splotchy and the car looked like the textured walls in my house. I was able to easily sand it…after HOURS of sanding, but I could have saved myself HOURS of work had I used the larger compressor. Go 60 Gal or bigger, dont even waste your time with anything smaller unless you are doing spot work. Smaller projects, individuals pieces, will do fine but a whole car requires more than 60 Gals. The calculations I later found was take the CFM of your tools, multiply it by 1.5 and thats the CFM you want out of your compressor
2 – The airlines – 3/8 inch seems to be an industry standard. Every part I found (regulator, filters, tubing kits) seemed to max out at 3/8 for fitting sizes. If you put a 3/8 fitting on a 1/2inch pipe, the air flow is restricted to that 3/8 fitting….so just go 3/8 all the way through. You will get the most consistant pressure/flow of air to the end. I have seen Kevin Tetz videos where he talks about the temp of the air and having a run of air line to allow the air to cool. Even my 26 Gal compressor tank would get warm….so I can see his point.
3 – The fittings – I never thought about air fittings prior to this. I always went to the hardware store, most stock 1/4 IM fittings for air hose QDs. They work great….but they are 1/4 inch. If you use a 1/4 inch fitting on your wall or compressor than no matter how big of a hose you use, the 1/4 is restricting. make sure you go 3/8T for your air fittings. I kick myself now because I have been doing automotive hobby work for years and never realized I have been choking my airflow with the wrong fittings.
I played with air pressures during my last primer application with my 26 Gal compressor, I increased my pressure and paid close attention to how the primer was spraying. With the maximum airflow (full tank) and a slightly higher pressure (80 at the regulator – 26 at the gun with trigger pulled) I saw awesome flow. As the tank emptied and the compressor kicked on I saw a decrease in smoothness of the primer application and the texturing got worse the more I went. I bit the bullet and picked up a 60 Gal compressor for under $500. I invested in a Rapid Air garage line kit, so now I have 3 fittings in the garage to hook up to. Wiring the garage for 220v cost me less than $100 doing it myself, but my fuse panel is right on the other side of my garage wall, so easy to trace the wiring. If you are investing the time and money into a large project….do it right and invest the money in your air set up