The Viair 400P portable compressor kit, currently priced around $180 on Amazon, offers a balance of speed and value for airing up tires. While not the fastest, it efficiently inflates 33″ tires from 16 psi to 35 psi. The 400P-A, with its automatic shut-off feature, adds convenience for around $35 more. Both models share identical performance specs: a 33% duty cycle at 100 psi (max pressure 150 psi), 2.30 CFM at 0 psi, and 1.75 CFM at 40 psi. Fill times range from 1:35 for a 31″ tire (15-30 psi) to 5:20 for a 35″ tire (0-30 psi).
A Viair 400P portable air compressor.
In real-world use, the 400P’s 33% duty cycle hasn’t presented any issues. Four 33″ tires can be inflated from 16-35 psi in approximately 12 minutes, well within Viair’s recommended 20-minute cool-down period for this duty cycle at 100 psi. While 100% duty cycle compressors exist, their lower output often results in longer overall inflation times. For instance, the Viair 450P, with 1.80 CFM at 0 psi and 1.39 CFM at 40 psi, takes 2:50 to fill a 33″ tire from 15-30 psi, compared to the 400P’s 2:05.
When comparing compressors, pay close attention to the pressure at which CFM ratings are measured. Some manufacturers, like Air Zenith and Smittybilt, advertise seemingly high CFM numbers at 0 psi, but lack data at working pressures – a crucial performance indicator. Conversely, the Puma compressor, often compared to the Viair 400P, boasts a 1.36 CFM rating at 90 psi, hinting at a slightly faster inflation speed, but potentially not enough to justify a higher price tag.
Checking tire pressure with a gauge
After extensive research, the Viair 400P and 400P-A offer excellent value. While onboard air systems with engine-driven or high-output electric compressors provide convenience, they often require significant installation effort. In scenarios where space is limited and permanent mounting is impractical, the portability and ease of use of the Viair 400P make it a compelling alternative to Air Zenith Obd2 12v Compressors and other more complex systems.
