High Diesel Temp AJM: Causes & Effects

Hello to all you experts.

First of all, I have to admit that I also used this '10c measure.'
But I'm starting to get a little worried about this. I once logged the diesel temperature while the engine was idling and the outside temperature was -1°C ---> ooohhh!!!? +129°C. I think that's probably a bit too much, isn't it? I actually thought the temperature increase would be in the range of 50 Kelvin, but +100°C or more?

I usually fill the tank completely or at least halfway to prevent fuel tank damage.
Now, here's my question for you: What are your current temperatures?
And how does this relate to the engine control unit and data synchronization before the cold start?
He doesn't really need to pre-glow, even with the cold outside temperature, because of the hot diesel mixture he's injecting. However, in reality, it's still -1°C.
I was just thinking that it started with a slight shudder in the cold.
I charged the battery again last night, but it's already been in there since 2000.
I'll disconnect the plug-in connection again.

Gibt´s da eine Verbindung im Steuergerät zu o.g. Wcertain?


I would be grateful for your explanations.

How did you measure that? Could it possibly be the temperature reading from a faulty temperature sensor?

Yes, exactly that fake sensor.
Comes with a built-in control unit (ECU). I now have about 2000 km of experience with the control unit. It runs noticeably better, but of course, I also wanted long-term stability. Current mileage is 115,000 km!
The AJM engine is designed to be quite stable from the factory, according to Volkswagen.
Apart from the timing belt drive, of course.

Yes, either I'm completely wrong and need to be corrected, or I'm not recognizing the problem.

The sensor fakes the actual temperature signal and tells the engine control unit (ECU) that the temperature is much higher than it really is. As a result, the ECU allows a slightly larger amount of fuel to be injected.

If you now log the temperature using VAG Com, you're not getting the real temperature, but a simulated one. Or am I misunderstanding something?

The fact is that the diesel temperature is rising, and that is unavoidable. However, I cannot say exactly how high it is.

matthiasTDI96 wrote:

Either I am completely wrong and need to be corrected, or I am not recognizing the problem. The sensor fakes the actual temperature signal and tells the engine control unit (ECU) that the temperature is much higher than it really is. As a result, the ECU allows a slightly larger amount of fuel to be injected. If you now log the temperature using VAG Com, you no longer have the real temperature but a faked one. Or have I got something wrong here?

No, it's fine .

Quote:

The fact is that the diesel temperature is rising, and that is inevitable. However, I cannot say exactly how high it is in reality.

Well, for that, it would need a switch. Then it could read the sensor values for logging.

I already understand how the fuel injection amount is increased.
I could also disconnect the device shortly after it starts up and log the data again.
(I'm not talking about minor deviations, but about significant ones. By 'significant,' I mean a difference of approximately 130°C at an outdoor temperature of 0°C.)
The full diesel tank won't immediately rise to +50°C in 5 minutes of idling; otherwise, we could solve the problem of morning coldness in the car by using the waste heat to heat the interior. (especially with PD injectors).
'No, I'm just wondering if anyone knows whether the preheating system uses the actual or simulated diesel temperature in its control, for example, during afterglow?'

I'm sorry if I didn't express myself clearly.
'Nevertheless, thank you for addressing this 'issue,' even though there might be more important things to do. However, I haven't been able to find what I'm looking for in the search function.'

Quote:

The full diesel tank won't immediately rise to +50C in 5 minutes of idling; otherwise, you could solve the morning cold in the car by using the waste heat to heat the interior. (especially PD elements)

No, the full tank won't warm up that quickly. But no one is saying that the diesel temperature in the tank decreases! The correct approach would be to have a sensor in the diesel return line, directly above the cylinder head. And it is quite possible for temperatures of almost 50°C to develop there in just 5 minutes.

Quote:

No, I just want to know if anyone knows whether the preheating system uses the diesel temperature, whether it's the actual temperature or a simulated one, in its control, for example, during afterglow?

Someone here definitely knows the answer. And if you use the search function more thoroughly, you can find out which component is responsible for the preheating duration...and that should answer your question.
Good luck.
Dirk.

Thank you for the explanation.

I've always thought that the temperature sensor was located in the supply line before the PD elements, sorry , I'm not an expert in the field, but I'm still interested in the technology.
I can picture that better now.
Then, of course, it becomes clear what's involved when it comes to cheating using the resistor.
The quality of this forum is what sets it apart from others.
Thank you.

I'm pretty sure that the afterglow time uses the water temperature as an input, not the diesel temperature. The diesel temperature is only used for interpolating the possible density. As far as I know.

Okay, and one more thing.

The temperature sensor is located on the cylinder head, on the right-hand side of the engine block when you open the hood and look towards the front. To find it, simply follow the diesel lines from the fuel injection pump (DIFI). You'll need to remove the plastic cover, and then you'll see the part; it's located on the right front side and is somewhat hidden.
But don't worry, there's also a fuel cooler installed under the passenger seat.
And if you want to heat the tank contents to 50°C, consider how long it would take you to boil 50 liters of water with a regular kettle. No, a TDI engine doesn't produce that much waste heat with an output of x thousand watts. Besides, the ambient air is also cooling things down.

It's possible that damage could occur in the summer with a completely empty fuel tank and extremely high temperatures, but that's just speculation on my part.

Eclipse_Fahren_TDI_Know wrote:

Always fill the tank completely or at least halfway to prevent fuel tank damage.

How do you mean that? Surely you have a plastic tank, right?

Der Kunststoff des Tanks kann auf jeden Fall mind. 300° C ab. I don't think so.
that damage can only be caused by issues related to the diesel return system.
Unless the return line is on fire...

Best regards,
Stefan.

I recall reading about an incident where a Volkswagen caused significant environmental damage due to a faulty fuel tank. I don't know the details, or even if it's true. Normally, the tank should be able to withstand the conditions, but the question is what type of plastic it's made of. Usually, high temperatures of the fuel haven't been a major issue in the automotive industry. Perhaps, in this case, a plastic was used for better crash protection, but one that has less heat resistance.

The AJM engine is designed to be quite stable from the factory, according to Volkswagen.

nasowas....where did you hear that? That kind of thing always calms me down immensely, as an old AJM diesel .

Hi Markus,

The AJM engine is designed to be quite stable from the factory, according to Volkswagen.

nasowas....where did you hear that? That kind of thing always calms me down immensely, as an old AJM diesel .

hello markus

Yes, I can confirm that; at least it doesn't fall apart into its individual components when standing .

It sounds almost like it's from an advertisement, but it's supposedly from Volkswagen itself:

3.3 Crankshaft
The forged crankshaft is a modification of the crankshaft used in the 1.9-liter 81 kW TDI engine. It differs from the original crankshaft by having an additional rolling process applied to the first crankshaft flange.

3.4 Connecting rods
The connecting rod of the 1.9-liter, 85 kW common rail engine is designed as a trapezoidal connecting rod. This design allows for 10% lower stress on the piston crown edge, 15% lower surface pressure in the piston boss, and reduces the connecting rod mass by 50 g (approximately 4%) per cylinder. The connecting rod is forged and designed as a split connecting rod. The latter provides high precision in the large connecting rod eye.

3.5 Pistons
The piston was designed as a cooled piston due to the higher thermal load compared to the current Volkswagen production engines. The use of high-temperature resistant aluminum alloys more than compensates for the mechanical strength loss that inevitably occurs due to the incorporation of a cooling channel. The cooled piston reduces the temperatures at the edge of the piston bowl by up to 40 K, the temperatures in the first ring groove by up to 20 K, and the temperatures in the pin boss by up to 10 K. The piston bowl was adjusted to match the new injection quality.

3.6 Crankcase
The crankcase is a standardized part that is identical to the current 81 kW production engine. When this crankcase is used in the common rail engine, fluid jet honing is employed in parallel with the distributor injection engines that are already in production. This type of honing reduces the engine break-in period and leads to lower oil consumption. Fluid jet honing and surface finishing represent an expansion of the known two-stage honing process by two additional steps. In the first new processing stage, high-pressure techniques are used to remove indentations on the cylinder liner surface, and to expose smeared scratches from the previous honing process, as well as cracks caused by the alloy composition. The resulting surface is largely free of metallic contaminants. In the subsequent final honing operation, the fracture edges created by the jetting process, as well as the remaining surface roughness in the apex area, are smoothed. Due to the clean surface, extremely fine diamond honing tools can be used during the honing process.I came across this about half a year ago, but I don't remember the source anymore.
The PD drive itself seems to be more problematic than it initially appears.
I think this might not be new information for some people.