Here's a bit more information.
The R-4 compressor's displacement is 10 cu-in. I couldn't find a chart, but it's power consumption is 9.4 hp at 2000rpm. The SD5H14 compressor displaces 8.4 cu in while the SD7H15 displaces 9.5 cu in. As you can see in the below chart, at the same 2000 rpm, the Sandens are consuming 3.75 and 4.0 hp respectively (1 kw = 1.34 hp)
The Sanden's are quite efficient as shown by the C.O.P which is the coefficient of performance ( calculated as power in/power out )
