General air compressor question

[TonyJ]

Compressor discharge size ( between pump and tank ) why are some really small like 3/8 - 1/2 and others like say mine on my Quincy 230 is 1 1/4 ? Would it be for cooling or for back pressure or what. I know even smaller pipe would carry the rated 24.8 cfm and I have seen other units being sold that has a much higher rated cfm using pipe smaller than 1 1/4. So my question is what’s really the point of such a large discharge. Intake is also 1 1/4. Point of note 230 is single stage

 

[The Cobbler]

it could be to enable the compressor's motor get up to full speed before it hits compression in the discharge line

 

[TonyJ]

it could be to enable the compressor's motor get up to full speed before it hits compression in the discharge line

That would be the unloaders job but however those old quincys didn’t have a tank check valve so the discharge line would always be under pressure because the exhaust valves did the job of holding the tank pressure

 

[The Cobbler]

yes & no.
while the unloader does unload the feed line to the tank check valve, if the line is larger vs smaller, when the motor starts, there is more volume in a larger pipe than a smaller pipe, so the motor has a chance to get up to full speed before it's met with more compression on the discharge side. I hope I explained myself! LOL

 

[TonyJ]

yes & no.
while the unloader does unload the feed line to the tank check valve, if the line is larger vs smaller, when the motor starts, there is more volume in a larger pipe than a smaller pipe, so the motor has a chance to get up to full speed before it's met with more compression on the discharge side. I hope I explained myself! LOL

I get what your saying and it does make sense BUT the older quincys don’t have tank check valves therefore the the feed line to the tank is always at tank pressure. The unloaders on the quincys and other models id say only holds the intake valves open until the pump gets up to speed and has oil pressure then allows the intake valves to open and close thus begins to build pressure. But maybe the idea behind the big 1 1/4 pipe is where it is always at tank pressure that the wall thickness of the pipe will withstand the constant pressure where a smaller line only has pressure when the pump is running when a in tank valve is used

 

[The Cobbler]

Thanks. I get you too!