I hope everybody understands a doubler.

It takes the incoming air pressure and doubles it. It does not increase the volume of air. Where it can be best appreciated is using the aux air compressor that is set to cut off at 80 or 100 PSI and doubling the pressure to 160 to 200 so tires that take 115 to use Paul's example can be filled.

FWIW my aux air compressor is set to cutout at 80 PSI. So I run my engine and use the 125 PSI the bus compressor is set to produce to fill my front tires. A doubler has 1/2 the flow rate, but twice the pressure. For those few times when I use aux air for anything other than the built in systems I will just run the bus if I need greater pressures. It is often not the pressure I need, but the volume and the bus air compressor can deliver a lot of volume of air.