CRD pumps - Why such a high pressure?

More or less - it's direct injection against combustion pressure after all....

...and diesel fuel is, like, a heavy oil or something!

Higher pressure = better atomisation = better burn = more power = better fuel economy = better emissions

Simple really, the smaller the droplets and hence the more quantity of droplets per say ml of fuel injected has a much greater surface area for the oxygen around them to burn more completely with.

As a rule the smaller the hole you force the fuel though the finer the mist you get, so to do it in a very short window you need immense pressure.

Results in cleaner, more efficient burn, and more work generated from the fuel injected. Tim..

Yes. That's basically what Diesel injectors do. The accelerator setting controls the length of the burn. And it's got to be injected against the pressure of any already-burnt stuff.

John

Dont forget that the most ancient and basic inline injection pumps running at only 1000psi, if that, are still capable of injectiing fuel into the cylinders against compression and combustion pressures.

Tim..