Another phenomenon | Beiträge 16+

[b]Another phenomenon[/b]
Can I contribute to the discussion: Despite the otherwise flawless cold start, the following behavior was noticeable: Starting at -5°C after a maximum of one second, and then after another second, it goes into a higher idle speed with a noticeable surge of gas:?: From then on, everything is normal. However, this was not the case in the last winter.

Regards, Andreas

[quote="Gremlin"]
The injection start or, more precisely, the position of the fuel injector for the injection start, depends on the pressure in the pump's internal chamber. This pressure is proportional to the pump's speed. That's why a minimum speed of 300 (starter) or 150 (pump for a 4-cylinder engine) is specified. Otherwise, the pressure generated by the fuel pump is not sufficient to initiate injection early enough.
Okay, I understand. Please provide the German text you want me to translate. I will translate only the readable text, leaving the HTML tags, BBCode tags, and URLs as they are.
Hi Gremlin,

I didn't expect the early adjustment to be active even at low idle speeds, although that's where there should be the least amount of spray and ignition delay (in degrees). :

Or should the fuel injection be initiated earlier when playing the organ, compared to, for example, during idle, so that the full injection volume is in the cylinder when the compression temperature reaches its maximum?
[quote]
It's possible that it could eventually start working, perhaps because the flaps of the pump aren't sealing properly, and the prolonged operation causes them to eventually make good contact with the wall, increasing the pressure. At normal operating speeds, this isn't a problem (due to the centrifugal forces). This is a conceivable possibility...
Sure, that's possible. But what should the impeller prevent, in the worst-case scenario, from attaching to the housing wall for 5 seconds or longer?

[quote='ulf']
Possible, perhaps. But what should the impeller prevent, in the worst-case scenario, from attaching to the housing wall for 5 seconds or longer? [/quote]
Hello Ulf,

Could this be related to the viscosity of the diesel? Doesn't the lubricating effect decrease with increasing temperature? Since diesel has become less sulfurous, it should also have significantly less lubricating effect.

Best regards,

Eike

[quote='ulf']

I didn't expect the early adjustment to be active even at the low starting RPM, although that's where there should be the least amount of spray and ignition delay (in degrees).
[/quote]
Yes, that makes sense. The pump is designed so that the injection starts earlier if the valve is NOT activated. 'NOT activated' = closed = the internal pressure is fully transmitted to the plunger.

When starting a cold engine, it is activated to 'maximum early' (this maximizes the ignition delay!), and when starting a warm engine, it is activated to a less aggressive setting. The injection start is only controlled during the pump's ascent, as there are no reliable signals from the NBF (presumably a sensor) yet.
[quote]
Possible, perhaps. But what should the impeller prevent it from sticking to the housing wall for 5 seconds or longer in the extreme case? [/quote]
Wear?
The VP44 even has notches on the wings to prevent camming due to the high internal pressure.

What's still on my mind: this problem seems to only occur at higher mileage (according to what I've read).

Theory:
The leaks in the pump and the wear on the nozzles are such that there is not enough injection at warm start. A cold start is possible because the maximum starting amount is set here. Perhaps the (already low) pressure is not enough to allow a good spray pattern. This would be further worsened by a low engine speed, as the steepness of the pressure increase depends on the speed of the pump plunger (= pump speed).
With a hard 10-cent coin, it should start immediately.

CU Gremlin

[quote="Gremlin"]
Yes, that makes sense. The pump is designed so that the injection starts earlier if the valve is NOT actuated. "NOT actuated" = closed = the internal pressure is fully directed to the plunger.

When starting a cold engine, it is actuated to "maximum early" (this maximizes the ignition delay!), while a warm start requires a less aggressive setting. The injection start is only controlled during the pump's ascent, as there are no reliable signals from the NBF (presumably a sensor or control unit) at this stage.
Hi Gremlin

These facts were already known to me.

But the early adjustment is actually meant to be used when [b]high [/b]
Balance the rotational speed and operating time of the "pressure front" from the pump to the nozzle (start of flow --> start of spraying).

Now, the starting and operating state with the lowest rotational speed, where the aforementioned time losses in degrees represent the lowest error.

Therefore, one could design the pump so that, for example, up to 500 motor rpm, the hydraulic pre-adjustment is still active even with the spray valve closed (= the internal pressure of the pump does not yet overcome the spring force on the spray valve piston), because later spraying starts are, in my opinion, never really needed :

For example, at idle (approximately double the starting speed), a small pre-adjustment could be used.

As mentioned: with the spray valve blocked = my warm engine does not start any better . . .

[quote='ulf']
But the early adjustment is actually meant to be used when the temperature is [b]high[/b]
Balance the rotational speed and operating time of the 'pressure front' from the pump to the nozzle (start of flow --> start of spraying) to minimize errors.

Now, the starting and operating state with the lowest rotational speed, where the aforementioned time losses in degrees of angle represent the lowest error.
Okay, I understand. Please provide the German text you want me to translate. I will translate only the readable text, leaving the HTML tags, BBCode tags, and URLs as they are.
...you have to read exactly what I write

The worst-case scenario for the diesel engine is the cold start, where the ignition delay is enormous (cold air, cold cylinder walls, poor injection, deposits on the cold walls...). Therefore, the injection start must be moved extremely early (the older diesels had a 'cold start accelerator' that did exactly that).

With a warm start, you don't need the extreme early adjustment ('with a warm start, accordingly less'). That's why I also have my theory about increasing leakage losses or poor spray patterns...

CU Gremlin

[quote="Gremlin"]
...you have to read exactly what I'm writing

The worst-case scenario for diesel engines is the cold start, where the ignition delay is enormous (cold air, cold cylinder walls, poor injection, condensation on the cold walls...). Therefore, the injection start must be moved extremely early (older diesel engines had a "cold start accelerator" that did exactly this).
Aha... I thought the cold start problems would already be solved with the pre-heating system.

The fact that the cold air still causes a significant ignition delay is new to me.

Because of the temperature increase due to compression...
[b]
IMO, it should always be the same.
And when the air in the engine compartment heats up by perhaps 40° (= difference cold - lukewarm start) in areas with hundreds of degrees, that didn't seem like a good "starting killer" to me.

But your argument from practice with the cold start accelerator is definitely unbeatable - I had completely forgotten about that, even though I once had a Peugeot 205 Diesel

[quote='ulf']

Aha... I thought the cold starting problems were already solved with the pre-heating system.
That the cold air still causes a significant ignition delay is new to me.

Because of the compression-related temperature[b]
rise
IMO, it should always be the same.
And if the air in the engine compartment heats up by perhaps 40° (= difference cold start - lukewarm start) in areas, then that didn't seem like a good starting experience to me
Okay, I understand. Please provide the German text you want me to translate. I will translate only the readable text, leaving the HTML tags, BBCode tags, and URLs as they are.
I'll see if I can get some protokoll data. But the fact that a completely cold cylinder can absorb a few degrees of compression heat in zero time is obvious. Otherwise, you wouldn't need to preheat

Direct injection injectors have the biggest ignition delay in diesels. If that's combined with a poor fuel spray pattern due to worn nozzles and low pressures...

But unfortunately, that doesn't explain the warm-start problems.
Suggestion: manipulate the temperature sensors to make the EDC think the engine is cold. If the start then goes smoothly, it's probably due to too low an injection amount. Or, try adding 10 cents to the fuel at start.

CU Gremlin

Hello everyone.

After my engine swap from 1Z to AFN, I also experienced the warm-start problems. It starts relatively quickly when cold, but it takes about 10-15 seconds to start when warm.
Then I read everything about it in this forum, and today I cleaned all the contacts and cables. And guess what!!: now it only takes about 3-4 seconds to start when warm. That's already a progress.
Maybe I'll replace the starter. The battery is new.

Regards,
Golfmann

The warm-start problems with the 66kw engine are a well-known issue and can be caused by several factors. Clogged fuel filter, faulty diesel return valve, worn-out 109 relay, and temperature sensor for the starter. The TDI engine's starting speed is temperature-regulated, as the engine starts better/worse at different temperatures. Addressing at least the first three causes will usually alleviate the problem.

[quote='Tagessuppe']The starting speed is regulated for the TDI engine, as the engine starts better/worse at different temperatures. [/quote]
I'd really like to get this explained.

I know how to control electric motors (it's my job), but without the right components in the car? Hmmmmmmmm....
I could swear that my TDI has a perfectly normal planetary starter

Looking forward to it

CU Gremlin

[quote="Gremlin"][quote="Tagessuppe"]The starting speed is temperature-controlled for the TDI engine, as the engine starts better/worse at different temperatures. [/quote]
I'd really like to get this explained.

I know how to control electric motors (it's my job), but without the right components in the car? Hmmmmmmmm....
I could swear that my TDI has a perfectly normal planetary starter

Looking forward to it

CU Gremlin
Who said there are no components for that in the car?

You seem to know everything about car parts. So why should I bother teaching a professional? Especially someone who works with electric motors every day?

Hi,

instead of dealing with a Gremlin, it would be much better if you could simply answer the question. Of course, other people, including myself, are also interested in your answer.

I'm also not clear on how the starting speed could be regulated... It draws 100 to 200A and is, as far as I know, directly connected to the battery. The only control I see is the reduction of the starting speed after prolonged organ playing decreasing battery :D

But please explain to me and others who are unfamiliar, where the temperature sensor is located and where the control input is made. ... I suspect that some part, which uses PWM or something similar at 200 amps, might be the issue.

[quote="Private Area"]
Hi,

instead of dealing with a Gremlin, it would be much better if you could simply answer the question. Of course, other people, including myself, are also interested in your answer.

I'm also not clear on how the starting speed could be regulated... It draws 100 to 200A and is, as far as I know, directly connected to the battery. The only control I see is the reduction of the starting speed after prolonged organ playing decreasing battery :D

But please explain to me and others who are unfamiliar, where the temperature sensor is located and where the control input is made. ... I suspect that some part, which uses PWM or something similar at 200 amps, might be the issue.
Okay, so I checked again.
The temperature sensor is the same one that measures the engine temperature. The starter speed is controlled by the control unit.

Hi,

[quote="Tagessuppe"]... The starting speed is controlled by the control device.[/quote]
Complete nonsense!

There isn't a single line from the STG to the starter! How would the STG then control the starter? The entire starting current is only switched on by the electromagnetic switch.
Have you ever calculated which currents flow there?
Let's assume a diesel starter has around 1.5 to 2kW - this means a smooth 125 - 166 Amperes at a voltage of 12V. Since the supply voltage is even lower during the starting process, you quickly reach 200 Amperes (or more).
Or why is the starter cable directly from the battery to the starter?
Why are we trying to keep this cable as short as possible?
Where would you put the control electronics that can handle such currents?
Definitely not in the engine STG and also not in the starter (electromagnetic switch). Imagine the cooling capacity you would need for such a control system.

GRINS

So, ich glaube, es wäre besser, wenn ich den Thread lösche, oder?
Obwohl es ja einen gewissen Unterhaltungswert gibt... aber dafür gibt es andere Foren :mrgreen:

Grüße, Rainer