Noozle / Injector for DB 990 Selectatatic

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JimCochrane
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Re: Noozle / Injector for DB 990 Selectatatic

Post by JimCochrane » Tue May 04, 2021 5:43 pm

See the service bulletin attached
Attachments
injector 1.JPG
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injector 2.JPG
injector 2.JPG (60.54 KiB) Viewed 165 times

JimCochrane
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Re: Noozle / Injector for DB 990 Selectatatic

Post by JimCochrane » Tue May 04, 2021 5:53 pm

Again see attached files re injectors
Attachments
1950-1988.JPG
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David Brown Injector Nozzle Tips 2.jpg
David Brown Injector Nozzle Tips 2.jpg (65.44 KiB) Viewed 163 times

JimCochrane
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Re: Noozle / Injector for DB 990 Selectatatic

Post by JimCochrane » Tue May 04, 2021 6:03 pm

A later service Bulletin . As you can see nozzles 6592 will service all earlier engines .
Attachments
injector 3.JPG
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rid54
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Re: Noozle / Injector for DB 990 Selectatatic

Post by rid54 » Tue May 04, 2021 6:07 pm

The amount of fuel injected, is determined by the injection pump, as long as the injectors are correctly adjusted (opening pressure). The spray pattern is determined by the nozzle design (needle and openings etc). Engine running depends heavily on proper spray pattern, as this will have an effect on combustion speed and starting properties.

If it is not totally impossible, it would be better to have the old injectors rebuilt by an expert, than to exchange them for newer, unless you can find the correct number of proper injectors and change them all out.

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db2d
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Re: Noozle / Injector for DB 990 Selectatatic

Post by db2d » Tue May 04, 2021 6:24 pm

It is not the size of the holes in the nozzle that determines the amount of fuel injected into the engine, it is the fuel injector pump that controls this.
The fuel injector pump delivers a precise amount of fuel and only this quantity enters the injectors and the combustion chamber. Use the CAV injector assemblies fitted with 6417 nozzles set at the appropriate pressure and this will be the correct combination for your engine.

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ollek
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Re: Noozle / Injector for DB 990 Selectatatic

Post by ollek » Tue May 04, 2021 7:23 pm

It has now been said several times that the hole size in the nozzle does not determin the amount of fuel injected to the engine and that the injection pump determins the injection prosedure has also been explained. A small variation (150 to 180 bar) in the injector opening pressure does not make any notable differnce to the amount of fuel injected or the injection timing but it will change the injection pattern. This is a diesel engine, not an petrol engine. Fuel injection does not work like carburators.

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cobbadog
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Re: Noozle / Injector for DB 990 Selectatatic

Post by cobbadog » Wed May 05, 2021 7:08 am

There is some really good information on those charts Jim, thanks for posting. Hopefully now armed with all the relevant information his injectors can be overhauled and work again.

bepel
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Re: Noozle / Injector for DB 990 Selectatatic

Post by bepel » Wed May 05, 2021 9:31 pm

Jim Thank you very much for your very helpful post.
That respond to my question and cleared some misinformation.
The nozzles are ordered and I await to see a improvement.

Thanks a lot

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