yet another phenomenon | Posts 16+

[b]yet another phenomenon[/b]
Can I contribute to the discussion? The following behavior was observed: The cold start itself was actually flawless, but after starting at -5°C and running for a maximum of one second, it then jumps to a higher idle speed with a noticeable surge . After that, everything is normal. So, this didn't happen last winter.

Best regards,
Andreas

Gremlin wrote:

du darfst jetzt aber nicht vergessen, dass der einspritzbeginn oder genauer die stellung des steuerkolbens für den einspritzbeginn vom druck im pumpeninnenraum abhängt. und der ist proportional der pumpendrehzahl. daher wird ja auch die mindestdrehzahl von 300 (anlasser) bzw. 150 (pumpe beim 4zyl.) vorgeschrieben. sonst reicht der von der förderpumpe erzeugte druck nicht aus um den spritzbeginn ausreichend früh zu steuern.

Hi Gremlin.

I wouldn't have expected the advance timing to be active at such a low idle speed, even though that's where the least amount of injection and ignition delay (in degrees) should occur .

Does the injection timing need to be advanced when playing the organ compared to, for example, idling, so that the full amount of fuel is injected into the cylinder before the compression temperature reaches its maximum?

Quote:

das er irgendwann doch anspringt könnte ja z.b. daran liegen, dass die flügel der förderpumpe nicht satt abschliessen und durch das lange orgeln dann doch irgendwann mal satten kontakt an die wand bekommen und der druck steigt. bei den normalen betriebsdrehzahlen ist das ja kein thema (fliehkräfte). wäre ne denkbare möglichkeit ...

It is probably possible. But what would prevent the pump impeller blades from coming into contact with the housing wall in extreme cases, for 5 seconds or longer?

It is probably possible. But what would prevent the pump impeller blades from coming into contact with the housing wall in extreme cases, for 5 seconds or longer?

Hello Ulf,

Could this be related to the viscosity of the diesel fuel? Doesn't the lubricating effect decrease as the temperature increases? Since diesel has become less sulfurous, it is said to have significantly reduced lubricating properties.

Regards,

Eike.

I wouldn't have expected the advance timing to be active at such a low idle speed, even though that's where the least amount of injection and ignition delay (in degrees) should occur .


Yes, it's currently in operation. The pump is designed such that when the valve is not activated, the injection start timing is advanced early. 'Not activated' means closed, which means the internal pressure is fully transferred to the adjustment piston.
During cold starts, the system aims for 'maximum early' ignition timing (resulting in the largest spark advance), while during warm starts, it uses a correspondingly smaller value. The fuel injection start is controlled only during the pump startup phase, as there are no reliable signals from the knock sensor (NBF) yet.


It is conceivable, yes. But what would prevent the pump impeller blades from coming into contact with the housing wall in extreme cases, for 5 seconds or longer?

verschleiss ?
The VP44 even has grooves on the vanes to prevent tilting due to high internal pressure.

What's still on my mind is that this problem seems to only occur after higher mileage (based on what I've been reading).

theory:
The leakage in the pump and wear on the injectors are occurring at such an unfavorable point that too little fuel is injected during warm starts. Cold starts are successful because the maximum starting amount of fuel is used then. Possibly, the (already low) pressure is not sufficient to create a proper spray pattern. This would be further exacerbated by a low engine speed, as the rate of pressure increase depends on the speed of the pump plunger (i.e., the pump's rotational speed).With a very strong 10-cent spark, it should start immediately.

CU Gremlin.

Gremlin wrote:

Yes, it's currently in operation. The pump is designed such that when the valve is not activated, the injection start timing is advanced early. "Not activated" means closed, which causes the internal pressure to be fully transferred to the adjustment piston. beim kaltstart wird auf "maximal früh" eingesteuert (zündverzug ist am grössten!), beim warmstart entsprechend weniger. der spritzbegin wird beim pumpenhochlauf nur gesteuert, da ja noch keine verlässlichen signale vom NBF vorliegen.

Hi Gremlin.

I was already familiar with these theoretical facts.

But the early injection timing is primarily intended to compensate for the ignition delay and transit time of the "pressure wave" from the pump to the injector (start of fuel delivery --> start of injection) at high revolutions.

Now, the starter organ's operating state with the lowest speed is where the aforementioned time losses, expressed in degrees of rotation, represent the smallest error.
Therefore, one could design the pump in such a way that, for example, up to 500 motor rpm, the hydraulic advance still keeps the injection timing at the late limit even with the injection control closed (i.e., the internal pressure of the pump does not yet overcome the spring force on the injection control piston), because later injection starts are probably never needed anyway .
For example, at idle speed (which is approximately twice the initial engine speed), a slight advance in ignition timing could already be used.

As I said: with the fuel injection limiter disconnected (meaning a slightly earlier start to fuel injection), my engine still doesn't start better when it's warm...

But the early injection timing is primarily intended to compensate for the ignition delay and transit time of the 'pressure wave' from the pump to the injector (start of fuel delivery --> start of injection) at high revolutions.

Now, the starter organ's operating state with the lowest speed is where the aforementioned time losses, expressed in degrees of rotation, represent the smallest error.



gnaaaa... you also have to read exactly what I write .

The worst-case scenario for a diesel engine is cold starting, where the ignition delay is HUGE (due to cold air, cold cylinder walls, poor fuel injection, and condensation on the cold surfaces...). Therefore, the start of injection must be advanced extremely early (older diesels had a 'cold start accelerator' that did exactly this).

When starting a cold engine, you obviously don't need the extreme early ignition timing ('use less advance when starting from cold'). That's why I have my theory about the increasing leakages or poor spray patterns.

CU Gremlin.

Gremlin wrote:

gnaaaa... you also have to read exactly what I write . worst-case für den diesel ist der kaltstart, dort ist der zündverzug RIESIG (kalte luft, kalte zylinderwände, lausige einspritzung, niederschlag an den kalten wandungen...). daher muss der einspritzbeginn extrem nach früh verlegt werden (die alten diesel hatten dazu den "kaltstartbeschleuniger" der genau das gemacht hat).

Ah... I thought the cold start problems were already solved just by using the glow plug system.
It's news to me that cold air can still cause a significant ignition delay.

Because the temperature increase caused by compression should, in my opinion, always be the same.
And if the air around a cold engine is heated by hundreds of degrees, but perhaps 40° less (= difference between cold and slightly warm start), then for me, that didn't have the quality of an "engine killer" .

But your argument from practical experience with the cold start accelerator is certainly unbeatable - I had completely forgotten about that, even though I once briefly owned a Peugeot 205 diesel .

Ah... I thought the cold start problems were already solved just by using the glow plug system.
It's news to me that cold air can still cause a significant ignition delay.

Because the temperature increase caused by compression should, in my opinion, always be the same.
And if the air around a cold engine is heated by hundreds of degrees, but perhaps 40° less (= difference between cold and slightly warm start), then for me, that didn't have the quality of an 'engine killer' .


I'll see if I can get any measurement logs. But it's clear that a completely cold cylinder doesn't consume those few degrees of compression heat in absolutely nothing; otherwise, we wouldn't need glow plugs .
'Direct injection systems have the longest ignition delay in diesel engines. And if the spray pattern becomes poor due to worn injectors and low pressure, that just makes things worse...'

But unfortunately, that doesn't explain the warm start problems.
Suggestion: Manipulate the temperature sensors to simulate a cold start for the EDC (Engine Control Unit). If the engine then starts easily, it's likely due to insufficient fuel injection. Alternatively, try adding 10 cents worth of fuel additive during startup.

CU Gremlin.

Hello everyone.

After I replaced my engine from a 1Z to an AFN, I also experienced starting problems when the engine was warm. It starts relatively quickly when cold, but when warm, it takes about 10-15 seconds before it eventually starts.
Then I read everything about it in this forum, and today I cleaned all the contacts and cables. And guess what?! Now, when it warms up, it only makes that noise for about 3-4 seconds. That's already a significant improvement.
I might end up replacing the starter motor. The battery is already new.

Best regards, Golfmann.

Warm-start problems with the 66kW engine are a common issue and can be caused by several factors, including clogged fuel filters, a faulty diesel return valve, an aging 109 relay, and a defective temperature sensor for the starter. In TDI engines, the starter speed is thermally regulated because the engine starts better or worse depending on the temperature. Addressing at least the first three of these causes often provides significant improvement in most cases.

Die Startergeschwindigkeit wird beim TDI waermereguliert, da der Motor bei verschiedenen Temperaturen besser/schlechter anspringt.

I would really like someone to explain that to me now.

I know how to control electric motors (it's my job), but without the corresponding components in the car? Hmmm...
I could also swear that a completely normal planetary starter motor is installed in my TDI .

with bated breath / with anticipation.

CU Gremlin.

Gremlin wrote:

Tagessuppe wrote: Die Startergeschwindigkeit wird beim TDI waermereguliert, da der Motor bei verschiedenen Temperaturen besser/schlechter anspringt. I would really like someone to explain that to me now. I know how to control electric motors (it's my job), but without the corresponding components in the car? Hmmm... I could also swear that a completely normal planetary starter motor is installed in my TDI . with bated breath / with anticipation. CU Gremlin

Who said there are no components for that in the car?
You seem to know every part of the car already. So why should I try to teach a professional? Especially someone who deals with electric motors on a daily basis?

Hello Tagessuppe,

Instead of creating a 'Gremlin' here, it would be better if you could simply answer the question. I'm sure other people are also interested in your answer (including me).

I'm also not clear on how the starter motor speed could be regulated... It draws its 100 to 200A and, as far as I know, is directly connected to the battery. Only the magnet that kicks the starter forward closes the contact, so the starter starts running. The only regulation I see there is a reduction in starter motor speed after prolonged operation due to a weakening battery.

'But please explain to me and the rest of us who don't know where the temperature sensor is located, and at which point the control system intervenes. ... I would say that if there were any component using PWM or something similar for 200 amps, I would have noticed it.'

PrivatBereich wrote:

Hello Tagessuppe, Instead of creating a "Gremlin" here, it would be better if you could simply answer the question. I'm sure other people are also interested in your answer (including me). I'm also not clear on how the starter motor speed could be regulated... It draws its 100 to 200 amps and, as far as I know, is directly connected to the battery. Only the magnet that kicks the starter forward closes the contact, so the starter starts running. The only regulation I see there is a reduction in starter motor speed after prolonged operation due to a weakening battery. But please explain to me and the other uninformed people where the temperature sensor is located, and at which point the control intervention takes place. ... I would say that I would have noticed some component that handles PWM or something similar at 200 Amperes.

So, I inquired again.
The temperature sensor is the same one that measures the engine temperature. The starter motor speed is controlled by the control unit.

Hi,

Tagessuppe wrote:

... The engine speed is controlled via the control unit.

Complete nonsense!

There isn't a single wire running directly from the TCU (Transmission Control Unit) to the starter motor! How is the TCU supposed to control the starter then? The entire current for the starter motor only flows through the magnetic switch.
Have you ever actually calculated what kind of currents flow there?
Let's assume a diesel starter motor has an output of around 1.5 to 2 kW. This means, at a nominal voltage of 12V, it draws a steady current of 125 to 166 amps. Since the supply voltage drops even further during the starting process, you can quickly reach 200 amps (or more).
Or why is the starter cable connected directly from the battery to the starter motor?
Why is it important to keep this connection as short as possible?
Where do you want to place the control electronics that can regulate these currents?
Certainly not in the engine control unit (ECU) or the starter motor (solenoid). Just imagine the cooling capacity you would need for such a regulating circuit.

SMILE.

So, I think it's better if I delete the thread, right?
Although there is a certain level of entertainment value, but there are other forums for that.

Best regards, Rainer.