Join Date: Dec 2001
Location: Belleville, Illinois
Thanked 22 Times in 17 Posts
Re: New Warn Winch out
Actually that's a pretty common way to rate compressors, and not really a bad way of doing it since there are reasons for wanting compressed air at different pressures.
0 PSI Gauge is actually 1 atmosphere, or 15 PSI absolute. If you're filling tires to 15 psi, that's two atmospheres absolute, so the flow will be half of what it is unrestricted. Tires to 30 PSI is 3 atmospheres, so the flow will be one third. If you want to run air tools at 90 PSI or 8 atmospheres absolute, figure on 1/8 of the volume.
The hitch in that is that compressors lose efficiency as the output pressure rises. That's when it becomes important to know how many stages a compressor has. A two-stage compressor is pretty efficient at 150 to 175 PSI. A single-stage compressor might eventually get there, but only be pumping a fraction of it's theoretical putput.
Actually Warn deserves kudos for showing that the rating is at 0 PSI output. They wouldn't really have to, but probably do because they expect their potential buyers to not be familiar with how compressors are customarily rated.