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Testing Viair’s 400P & 450P Portable Air Compressors

Testing Viair’s 400P & 450P Portable Air Compressors

Ali MansourPhotographer, Writer

Practically every time our tires hit the dirt, we air down. It makes such a tremendous difference in the ride quality and performance of the vehicle, it’s absolutely silly not to. Airing back up is probably one of our least favorite wheeling rituals. It signals our time in the dirt is over, and we have to wait (sometimes 30 minutes) to get our tires back to street pressure. We’ve tested an assortment of onboard and portable air systems over the years and one of the companies we’ve had great success with is Viair.

Viair offers a range of air systems, which span the spectrum from basic compressors to comprehensive dual-pump and tank combinations. The company even offers Jeep-specific kits. While we like the hard-mount systems, we were interested in testing the performance of the company’s portable wares. The major advantage of the portable system for us is that it allows us to have a compact air compressor setup for multiple rigs.

Choosing the right compressor can be a little tricky. While Viair does a great job suggesting the correct compressor kit for your rig based on tire size, understanding how the systems work can actually allow you to make the most informed decision. To delve a little further into this, we picked up two of Viair’s premium portable air compressors: the 400P and 450P. The 400P is part of the company’s Heavyweight Series and has a 33 percent duty cycle. The 450P comes from the Extreme Series line of Automatic Portable compressors and boasts a 100 percent duty cycle.

Duty cycle is something you’ll read about plenty when it comes to air compressor literature and is why we wanted to test both the 400P and 450P. Essentially, a duty cycle refers to the amount of time the compressor can be run before needing to cool down. Viair rates it 400P 33 percent duty cycle compressor with a use time of 15 minutes on and 30 minutes off. The 450P, with its 100 percent duty cycle, is designed to have a one-hour continuous run time. This rating is for 100 psi with a standard ambient temperature of 72 degrees.

On paper, the 100 percent duty cycle seems like the most logical option, as nobody likes waiting around for their air compressor to cool down, especially for 30 minutes. The difference between the two often comes down to speed. While the 450P can absolutely run long, it’s actually going to be slower than the 400P. To put this in a real-world comparison, we tested the two compressors on two separate Jeeps. Here is what we found.

Compressing Thoughts

So which compressor do we think is the better fit? Viair suggests the 400P for those running up to 35-inch tall tires. We tested both on 37s. There’s no question that the 33-percent duty cycle compressor is faster per tire, which we like. However, you could run into the situation where the compressor needs to cool down for 30 minutes before you can finish airing up that last tire fully, which would negate the speed advantage.

We found the 450P is like a steady workhorse. It seemed quieter and smoother, as well as cooler to the touch, over the 400P. Our average times were close to the best times we posted, but we found that the provided gauge was a couple pounds off of our other two tire gauges. As such, we spent some extra time double checking the psi for consistency.

We definitely enjoyed the clamp-on style inflation gun that both systems came with and found the extension hose was plenty long for both rigs. Ultimately, both are great compressors, but the consistency of the 450P might edge a slight advantage over the speed of the 400P.