Why is pressure in a common rail fuel system so much higher than in an air compressor or supercharger?

Superchargers in cars are bulky, expensive, consume considerable amount of engine's power and yet they generate only about 6-9 psi boost. On the other hand, modern common rail diesel engines inject fuel into the cylinder at 36,000 psi. Naturally, superchargers handle a much larger volume, but still the discrepancy is shocking. I suppose it is easier to generate pressure with a liquid which is not compressible, but why exactly is that?

• Just consider the differences in volume flow rate, then think about density and viscosity... All the reasons are there. Sep 13, 2021 at 12:21
• @SolarMike a lean air-fuel ratio is 14.7:1. But it is mass ratio. When we convert that to volume ratio, because of the air's 625 times lesser density (compared to gasoline), we get volume ratio of 9187.5:1. Okay, now I think I get it ;) Sep 13, 2021 at 12:51
• Isn't 14.7:1 stoichiometric? Sep 13, 2021 at 13:16
• Have you even looked at the size difference between a car and a rail locomotive? Sep 13, 2021 at 13:27
• @CarlWitthoft I mean en.wikipedia.org/wiki/Common_rail Sep 13, 2021 at 13:49