Re: high pressure vs high volume
High volume is measurement of how MUCH fluid a pump can deliver in a given period of time. A bilge pump is usually rated at (for example) 500 gallons per hour but its output is at relatively low pressure (PSI). High pressure means a fluid is being pumped into a specific cavity at (for example 100 pounds per square inch (PSI). Your home water system contains water under approximate 80 PSI for example. The oil pump in your engine creates pressure in your engine at approximately 40-60 PSI. The amount of oil (volume) in the engine doesn't matter unless there is none in the crankcase in which case oil pressure goes to zero (a bad thing). Therefore pressure and volume are really unrealated. You can have a small pump that creates very high pressure but doesn't deliver much volume (gallons) like the fuel injection pump on your car. Or you can have a pump with relatively low pressure that delivers very high volume of material (like a bilge pump).
