Needle Valve Injector (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 engines? The reason for my question is that, during injection, the "needle" in the needle lift injector moves and communicates the amount of fuel injected to the control unit via a change in resistance. The control unit then adjusts the injection quantity up or down using the quantity adjustment mechanism. Please correct me if this 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 designed with larger dimensions to achieve a similar "needle lift" with a higher fuel volume?
If you were to theoretically install a naturally aspirated engine (NHG) from a 110 horsepower engine into a 90 horsepower engine, but use the fuel injector size of 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 flow meter in 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 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 to be complete: 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 injection holes. The injection holes are opened when the needle lifts from its seat.
In the VEP-TDI injectors, 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 recommended here, for example, on Rainer's website.

Regards,
Alex.

@donalexo and the other readers.

When I wrote about the channels in the NHG (High-Pressure Gasoline Injector), I wasn't referring to the ones in the nozzle itself, but rather the area where the needle sits. The standard nozzles are actually composed of a nozzle and a nozzle holder, and I assumed that the NHG was similar. Regarding the function of the NHG, I meant something along the lines of what you described; my explanation might have been poorly worded. I thought the control unit received signals about the amount of fuel injected, not the start of injection. Anyway, I spoke briefly with the local Bosch service center about it, but they couldn't tell me whether the signals from the 90 and 110 HP NHG injectors are similar or completely different. It's possible that someone there might have dealt with them before you decided to install the larger nozzles.
Are there any more accounts of people who have installed larger injectors in otherwise stock 1Z engines?
Are there actually any injector nozzles from other manufacturers that have a diameter between 0.184 and 0.205 mm, which are compatible in terms of opening pressure, and also match the shape (I suspect that, for example, Bosch specifies the nozzle shape to the engine manufacturer)?
I hope this time it's accurate and technically correct.

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 fail quickly!

Quote:

I was previously at the local Bosch service center and discussed it with them [/b]roughly[/b].

...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 modification will affect the system, I suggest you avoid making any alterations.
Please don't misunderstand my tone; I'm just offering some well-intentioned advice before you damage your engine.

Regards,
Alex.

[Translating...]

Siehe Info zum Nadelhubgeber: https://community.dieselschrauber.org/en/viewtopic.php?t=19155

Only the 150-degree spray angle injectors designed for the 4/5-cylinder VEP-TDI engines will fit, specifically those with the part number DSLA 150Pxxx.
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, as well as experiences with jet tuning.
In short, injectors with a flow rate of 0.205 usually work quite well in the 1Z engine, while those with a flow rate of 0.216 are somewhat borderline in terms of EGT (exhaust gas temperature), soot production, and air mass.
When experimenting, avoid using used, larger, or unverified nozzles, as the engine is very susceptible to damage.