I’m getting ready to purchase and install a Viair 450c air compressor to the frame of my F-250 to fill tires back up to 70 psi and top off airbags as needed. I’m planning on using uplifter switch in the cab to turn it on and off. If I understand this correctly, I’ll need to run power to my uplifter and then to the relay. The relay is then grounded. I then need to run from the battery to a 40a fuse, to the relay, then out the relay to the compressor. I’m reading that it needs a pressure switch and it needs to be installed before the ground on the relay. Is this so the compressor doesn’t exceed its 150psi working pressure?
On Board Air Compressor Installation Questions
- Thread starter Pilotamis
- Start date
Martyn
Supporting Sponsor, Overland Certified OC0018
100% cycle duty is good but I think you will be waiting a long time to fill the tires up to 70 psi. The cfm rating for this unit is 1.8cfm at 0 psi. A single compressor like this with a 2.5 gallon air tank would help, but once the air in the tank starts to get depleted I believe things will go slow. I have an Extremeair Magnum with a 2.5 gallon air tank on my F250, it is rated at 6.0 cfm at 0 psi, and it still takes a while to re-inflate my tires for 20 psi back up to 55 psi. Have a good think and make sure you have done your research before installing your air system. Compressors and tanks are expensive and time consuming to install and after it’s said and done you need a system that performs up to your expectations.
shade
Well-known member
Good advice. When I was shopping, I was choosing between a VIAIR 400 & 450. When comparing the performance charts, it appeared that the way that they got 100% duty cycle out of the 450 was by detuning the 400 to reduce load/heat. For my use, the 400 was the better choice.
I have to say that I was kinda let down by the performance of my Viair 450P in bringing my 39X12.50R17's back up from 15PSI to 35PSI. I have a 7 gallon air tank and I believe I will be designing a system to utilize that in conjunction with the Viair and see how that performs.
I ordered the 450H. I wanted the ARB twin, but funds don’t really allow it. I’m worried without the tank that it’ll take a long ****** time to fill the tires back up, but for this trip we’ll have a lot of time on our hands. We’ll see how it goes. It should be here this week and I’ll give it a time test.
DaveInDenver
Middle Income Semi-Redneck
For a tank to help it needs to substantially fill the tires without making the compressor work. Have to figure out how much volume is in a 39x12.50x17 tire. If I did my hasty calculation it's about 5.6 cubic feet. Roughly speaking 7 gallons of volume is approximately 1 cubic foot. So if you keep the tank at 100 psi it will increase one tire 17.9 psi. After that it's just extra volume for the compressor to work to fill in parallel to the tire. That 5.6 cu-ft seems a bit high but I don't think it's grossly off.
You could say I kinda have a grasp on what I need. I'm a factory tech for a compressed air manufacturer. The Viair was a last minute add on to my packing list. V2.0 will be more than sufficient! ;-)
DaveInDenver
Middle Income Semi-Redneck
So you think 7 gallons is enough?
There is NEVER enough compressed air storage! But in this case I believe 7 gallons at ~150PSI will be sufficient to speed up the process a great deal. If space permits the tank may actually wind up being two-six gallon tanks, but I have to get under the truck and do some measuring first. I also need to try to wrangle an auxiliary gas tank under there somewhere. Space runs out fast on a standard cab compact truck!
The PSI is rated on my 450P at 150PSI so if I keep my tank(s) at close to that pressure it will improve the speed of filling that first tire. The compressor can keep going while my fat slow self gets around to the next tire. It's isn't as good as having a 10HP shop compressor with a 100Gal tank but if it beats the 30+ minutes tank-less normal time I will consider it a success.
DaveInDenver
Middle Income Semi-Redneck
Even at 150 psi I don't see how it will help more than one or maybe two tires at which point it's just extra volume for the compressor to have to work filling. The ideal gas law just reduces to this, right?
You are correct on the ideal gas law but you're missing the forest for the trees, don't be greedy. If it only helps with two tires that's at least a third, maybe even a half cut off refill time. To me that's a big improvement! I'm not building an F700 based Earthroamer sized outfit, I'm building a compact pickup into a road capable, rock crawling adventure rig.