AAZ 2 stage injectors? Anyone explain?

[Baxter]

I just had a search of the old topics and Im struggling to find an explanation.
Can anyone explain the 2 stage injectors fitted to the AAZ? Someone said it was 2 springs inside? How do you test them? What are the benefits/pitfalls?
Basically, Im just looking for a bit of a description, someone asked me the other day and I couldn't answer, I said I didn't know but would try to find out for them, so here I am!

[Baxter]

No one?

[QuickTD]

Quoting myself from another post,

The 2 spring injectors are pretty simple. At low flow levels (idle and light load) the injector operates on the primary spring in the same manner as a conventional injector. As injected quantity increases, pintle lift increases and the pintle contacts a second, heavier spring (through a shim) that increases the pressure needed to further lift the pintle. As a result, at high loads and throttle settings the injection pressure increases.

 The advantages of the 2 spring setup are, quieter operation under light load, better atomization under heavy load. Proper testing involves equipment that can measure pressure at a given flow rate, these machines are beginning to show up in diesel injection shops in north america. For our purposes, I think it's safe to just not disturb the setting of the second stage spring and just adjust the breaking pressure of the first stage when changing nozzles.

[Hey]

You will find your answer there: (toward the end)


http://vwdiesel.net/phpBB/viewtopic.php?t=3983