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Engine Specific Info and Questions => IDI Engine => Topic started by: Baxter on May 28, 2006, 03:25:46 pm
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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!
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No one?
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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.
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You will find your answer there: (toward the end)
http://vwdiesel.net/phpBB/viewtopic.php?t=3983