Needle Valve: Types, Function & Applications (07-12-2003, 15:49)

hello

"Does anyone have experience with needle lift injectors? Are the internal channels in the 110 HP engine injectors larger than those in the 90 HP engine injectors? The reason for my question is that, during injection, the "needle" in the needle lift injector moves and, through a change in resistance, informs the engine control unit (ECU) about the amount being injected. The ECU then adjusts the injection quantity up or down using the quantity adjustment mechanism. Please correct me if my understanding is incorrect."
With the 110 hp engine, more diesel fuel must flow through (at least when using full throttle) in the same amount of time. Do these control units use different resistance values, or are the injectors sized larger to achieve a similar "needle lift" with a higher fuel volume?
or, to put it another way: if you were to theoretically install a naturally aspirated head (NHG) from a 110 horsepower engine into a 90 horsepower engine, but using the injector nozzles from the 90 horsepower engine, what would happen?

best regards, christian

@audi 80 tdi:

Your understanding of how an NBF works is unfortunately incorrect .

The NBF (Nozzle Back Pressure) sensor does not control the diesel injection quantity; it only provides a feedback value to close the injection timing control loop. This means that the movement of the nozzle needle generates an electrical signal, which is used by the EDC (Electronic Diesel Control) to regulate the injection timing. The injection quantity is controlled by the quantity control mechanism of the pump. The NBF has absolutely nothing to do with this!
Based on your explanation, it seems you believe the NBF functions similarly to a potentiometer. However, this understanding is also incorrect. It's a non-contact method of signal generation (inductive), where a permanent magnet attached to the extended nozzle needle enters a coil. The movement of the nozzle needle then induces a voltage, which is interpreted as an opening pulse by the EDC.

Regarding your other question: The NBF (Nozzle-Based Fuel Injector) for the 110 horsepower engine variants, of course, has larger spray holes in the nozzle. Just for the sake of completeness: The NBF consists of a nozzle holder with integrated electronics (sensor) and the actual fuel injector.
The injector nozzle protrudes diagonally into the combustion chamber and typically has 5 nozzle holes. The nozzle holes are opened when the nozzle needle lifts from its seat.
In VEP-TDIs, two-spring nozzle holders are used, which enable a pre-injection and a main injection (pre-stage and main stage).

I hope I was able to convey the most important information to you. For more detailed information, I can recommend relevant literature, which is, for example, recommended on Rainer's website.

Regards,
Alex.

@donalexo and the other readers.

When I wrote about the channels in the NHG (high-pressure gasoline injection system), I wasn't referring to the ones in the nozzle itself, but rather the ones in the area where the injector sits. The standard nozzles are actually composed of a nozzle and a nozzle holder, and I thought the NHG system was similar. Regarding the function of the NHG, I meant something along the lines of what you described, although my explanation might have been a bit unclear. I thought the control unit received signals about the amount of fuel injected, not the start of the injection. Anyway, I was at the local Bosch service center and briefly discussed this with them. However, they couldn't tell me whether the signals from the 90 and 110 HP NHG systems are similar or completely different. It's possible that someone there might have worked on these systems before you decided to install the larger nozzles.
Are there any more user experiences available regarding the installation of larger injectors in otherwise standard 1Z engines?
Are there any injector nozzles from other manufacturers that have a diameter between 0.184 and 0.205 mm, that are compatible in terms of opening pressure, and of course, that have the correct shape (I suspect that, for example, Bosch specifies the shape of the nozzle to the engine manufacturer).
I hope this time it's accurate and free of errors (in terms of content).

best regards, christian

@audi 80 tdi:

Quote:

I suspect that, for example, Bosch, the engine manufacturer, determines the shape of the nozzle

.

I think it's quite the opposite. After all, the engine designer determines the shape of the piston recesses, and thus the combustion chamber geometry. The ESD (Electro Spray Deflector) must then be precisely matched to this geometry. That's why you probably won't be able to install nozzles from other manufacturers in your engine. Even a small change in the nozzle installation angle in the cylinder head would result in a completely different arrangement of the spray holes. If you were to install such an injector, your pistons would likely be ruined very quickly!

Quote:

I was previously at the local Bosch service center and discussed it [/b]roughly[/b] in detail

.

...that's exactly what it sounded like!

Here's my advice: Before you start making any changes to your fuel injection system, I would strongly recommend that you familiarize yourself with how it works. The relationships involved are quite complex, and even the smallest change can have a cascade of consequences. Until you understand how each change will affect the system, I would advise you to leave it alone.
Please don't misunderstand my tone; I'm just offering some friendly advice before you ruin your engine.

Regards,
Alex.

See information about the needle feed mechanism: https://community.dieselschrauber.org/en/viewtopic.php?t=19155

Only the 150-degree spray angle injectors designed for the 4/5-cylinder VEP-TDIs, specifically the DSLA 150Pxxx type, are compatible.
I am not aware of any sizes between 0.185 and 0.205.
There's plenty of reading material available here about the pros and cons, and experiences with jet tuning.
In short, 0.205 injectors generally work well in the 1Z engine, while 0.216 injectors are somewhat borderline in terms of EGT, soot, and air mass.
When experimenting, avoid using used, larger, or unverified nozzles, as the engine is very susceptible to damage.