Best PSI to run the horns at
For actual train horns such as Leslies and Nathans, run them at 150psi or below. Running them at 200psi changes the tone of the horn, and actually decreases the decibel level. It is only louder to the human ear.

For the shocker series horns… The shockers are a tough horn and can be ran up to 200psi, with half inch line such as in the XL kit, it is suggested to run them at 150psi for an actual train tone. With the normal conductors special with 5/16ths line, 200psi sounds amazing, Its noticeably louder than 150psi and I highly recommend it.

For other horns such as Kleinn and such. I saw in the terror of the streets videos, Hornblasters used 175psi on the horn, I have used 200psi on the original valve for a couple of years and it still works fine and sounds great too. I would say 200 and below, just like the shocker series horns.

Best Air size to run horns at
For actual train horns such as Leslies and Nathans, ½” works great, anything less and your restricting the airflow to the horn.

For shockers and Kleinns, either the 5/16” or ½” line works. With ½” line, the horns will draw more air, making them louder, however since it draws more air, you will go through your air supply faster.

Optimum Tank size
If you own or want to own an actual train horn such as a Nathan or Leslie, 5 gallons is the minimum. Leslies use more air so I would recommend more than 5 gallons. The bigger tank the better for these horns. And as with VIAIR’s warranty, 5 gallons of tank per compressor. Oasis compress can handle a much larger tank size so that doesn’t apply to them.

For the occasional honker, who doesn’t go around blasting everyone, just uses their horn in emergency situations…
~2 gallons is fine, I used it for about a year and 2 gallons worked, I later upgraded to a 5 gallon because I was sick of hearing the compressor all the time.

What is CFM?
The notation CFM (Cubic Feet per Minute) refers to a volume of air produced by the air compressor at a given pressure or PSI (Pound per Square Inch)

What is Duty Cycle?
A compressor's duty cycle determines the percentage of run time in a full cycle. A full cycle is determined by adding the compressor run time to its rest time.

Does a compressor that has 100% Duty Cycle mean that I can run the compressor all the time? Can I run my compressor 24 hours a day?
No, you've got to remember that duty cycle is rated at 100PSI, at an ambient temperature of 72°F, but certainly a 100% duty cycle compressor can run for much longer periods of time than a 30% duty compressor under the same conditions.

I'm interested in a compressor for my on-board setup. Which compressor would you recommend?
We would recommend either the 400C 12V air compressor or the 450C 12V air compressor for your setup.

Does a new compressor have to be broken in?
No, they do not. Typically after an install, you should power up the system from 0 to whatever the cut-off pressure is and check for any leaks that may be present.

How do you check for leaks?
You can check for leaks by putting soap and water solution where the fitting connections are. If there are bubbles present that grow in size, then there are leaks.

Does it matter where I install my compressors on my vehicle?
This depends on several factors such as available space, whether or not the compressor is of a sealed or vented type, as well as personal preference and aesthetics. Make sure to utilize the rubber insulators to keep vibration and noise to a minimum.

How can I tell whether the compressor is sealed or non-sealed?
Manufacturers will normally specify if a compressor is sealed against moisture and dust, and in many cases, you can tell the difference by simply inspecting the compressor. If you see vents, cracks, or holes in the motor housing, then the compressor is not sealed and must be kept away from dust and moisture.

Why is it important to have a sealed and moisture-resistant compressor?
The preference of a sealed-type compressor is due to the fact that in mobile pneumatics, compressors are likely to be exposed to outside elements.

Is the 550C compressor sealed and weatherproof?
The 550C is not a sealed unit. If you want to mount a compressor under your truck, you might want to take a look at our 450 series. While it is not as fast as the 550 series, it is moisture and dust resistant and can be mounted under your truck. Also, we have new compressors that are more suited to exterior mounting (420, 460C, and 480C).

Is it possible to mount the compressor sideways? Must it be mounted with the cylinder upright?
Yes, you can mount our compressors in any direction or position because they are oil-less. The only position we do not recommend is an upside-down mount, since heat tends to travel upward.

If I mount my compressor sideways, like on the frame rail of my truck, is there anything I should be careful of when doing this?
If you mount your compressor sideways to the frame rail, you should periodically check to make sure that your compressor is mounted securely. Use a thread-locking compound to keep the screws from backing off and causing the compressor to be mounted loosely.

Is it possible to hook up more than one compressor to a single pressure switch?
Yes, it is possible to use one pressure switch on more than one compressor. You should always run a relay if you want to hook up multiple compressors to a single switch. You should check the amp draw on the switch first, and then you'll know how many compressors you can hook up to one switch.

Can I use an adjustable pressure switch with my compressor?
We don't recommend that you use adjustable pressure switches with any VIAIR compressor. If you use an adjustable pressure switch, you can set the pressure switch higher than the maximum pressure that is rated for your compressor, or you may exceed the maximum rated working pressure for your air supply tank. Doing so will immediately void your warranty, not to mention, it is dangerous.

Is amp draw of the compressor something I need to be concerned with?
Yes, the lower the amp draw, the better the compressor is. As a rule of thumb, the maximum amperage that a compressor should require is 30amps.