Wann beginnen TDIs zu rußen? | Posts 16+

For the sake of accuracy, I would like to reiterate that a 'sudden increase in soot emissions due to turbo lag' cannot occur in a properly functioning TDI engine.

I would like to disagree with you, because I haven't encountered a single TDI, even one straight from the factory, that doesn't produce some black smoke when you accelerate hard.

The soot might not be present if the actual values precisely matched the target values, especially those of the turbocharger and the mass airflow sensor.

peter

It was actually clear that such a comment would have to come from you, as a notorious hater.

Umm...turbo-hater? Did I miss something ?

For the sake of accuracy, I would like to reiterate that a 'sudden increase in soot emissions due to turbo lag' cannot occur in a properly functioning TDI engine.

...it seems you may have overlooked the fact that even brand new cars, when driven at full throttle for a long time, then briefly at partial throttle, and then again at full throttle, can emit a small puff of soot. Or is that not possible because it's not in the textbook?

Oh, yes, of course, they're all modified. *taps forehead*

In the 'Important' thread regarding the particulate matter issue, I have once again brought up the two theses that are circulating about the acceleration soot surge: /viewtopic.php?t=9067&postdays=0&postorder=asc&start=24

Regards,
Holger.

The soot might not be present if the actual values were to precisely match the target values, especially those of the turbocharger and the mass airflow sensor.
Hi Peter! Perhaps the air volume in the intake manifold between the turbocharger and the engine is playing a role? This volume needs to be 'charged' first due to its storage capacity, so that the mass airflow sensor (MAF) reports a high mass flow rate early on, even though the actual mass flow rate into the cylinders is lower (because a portion of the MAF's mass flow is 'used' to charge the volume).

Since this dead volume is very small, it can only be a very dynamic phenomenon that occurs when there is a very rapid transition from thrust cutoff to full power.

This black smoke emission, in my opinion, can be avoided by incorporating dynamic factors into the engine maps.

Regards,
Holger.

Hi,

However, it's important to remember that after a period of idling, the next burst of acceleration can push some of the soot particles that have accumulated in the exhaust system out the back - this is likely the explanation for the acceleration-induced smoke cloud, assuming a properly functioning, untuned engine.

Best regards,

Jan.

Hi Jan,
but please also remember that, especially after a longer period of idling, the next burst of acceleration will push some of the soot particles that have accumulated in the exhaust out the back.

Interestingly, I also observe these soot particles even when the brief period of operation between two full-power phases is extremely short, or even when the engine only runs for a short time with the thrust cut off.

In my opinion, this contradicts the 'dust cannon' theory. The soot cloud must be caused by regulatory reasons within the engine management system.

Regards,
Holger.

Hi,

That could very well be true... especially considering my observations in Berlin's city traffic suggest that the "Russian roulette" phenomenon (referring to potential engine problems) is more frequently observed in CR/PD engines than in VE-TDI engines (just to tie in with the parallel thread).

Best regards,

Jan.

The Russian cloud has completely different reasons:

To minimize turbo lag, I need to ensure a large exhaust gas flow as quickly as possible. In this operating condition, this is only possible by initially running the engine with a slightly rich fuel mixture. If the engine is operated exactly at the soot limit, it will become sluggish and react slowly to driver inputs.
This phenomenon is familiar to many Euro-4 vehicle owners.

CU.

To keep the turbo lag as small as possible, I need to ensure a large exhaust gas flow as quickly as possible. This is only possible in this operating condition if I initially enrich the mixture slightly.

It is precisely this assumption that I have already expressed in the parallel thread https://community.dieselschrauber.org/en/viewtopic.php?t=9067&postdays=0&postorder=asc&start=24. This would be a deliberately induced, temporary exceedance of the soot limit.

The term 'over-oiled' has no place in diesel engine technology, in my opinion, because neither homogeneous mixtures nor lambda values less than 1 are present here.

This puff of black smoke, in my opinion, is avoidable by having the characteristic curves take into account dynamic factors.

Then the control unit would have to 'think ahead.'

I think the biggest problem is the turbocharger's inertia.

I'm interested in how it looks from a soot perspective, specifically when it comes to register charging.

Okay, here are some calculated lambda values, derived from the series-blurring kernels (with a 1-day delay ).

Generally, the "richest mixtures" are...
-> Allowed to operate with low RPM, likely to enable high starting torque without wheelspin.
-> Suitable for use with medium to high air mass conditions (i.e., increasing or full boost pressure) in the mid-RPM range.

The number pairs represent air mass [mg/stroke] / Lambda, with the latter being calculated as air mass / (diesel mass * 14.5).

Generally, I have listed the "richest mixture" for each air mass, which is often only used at a specific engine speed.
In the lower air mass region, I also refer to the mixture with the highest concentration as the "richest mixture."

1Z:
500 / 1.19, increasing to 850 / 1.54.

AFN:
450 / 1.19 . . . 600 / 1.18, increasing to 950 / 1.49.


AVB (PD 74 kW EU3?):
450 / 1.07, increasing to 1000 / 1.38.

AJM:
550 / 1.12, increasing to 1000 / 1.30.

ASZ Version 1:
450 / 1.15, increasing to 1076 / 1.26.

ASZ Version 2:
450 / 1.07, increasing to 1050 / 1.21.

ARL:
450 / 1.07, increasing to 1076 / 1.24.

BPX (1.9L, 160 hp):
450 / 1.29 . . . 650 / 1.21, increasing to 1076 / 1.16.


Generally, it is observed that...

1. The PD technology is already used from the factory to operate with less air excess, thereby saving energy.

TDIs can often operate with significantly higher levels of "sootiness" than the initial lambda values for incipient soot would allow.

I like the thread.
I'd like to add that I'm using ALH injectors with a flow rate of 0.205, which means approximately 20% more diesel is injected within the stock injection range. I've noticed that under full load and during nighttime driving, I definitely see some soot in the headlights of the vehicle behind me. During daylight, I don't believe I see any soot at full load. However, this 20% is far below the 48% mentioned. If your calculations are correct, it seems that factors like injection pressure and swirl are of very high importance and shouldn't be neglected during tuning.

Read carefully!

The +48% refers to the AKU (air-fuel ratio) compared to the ALH (engine). Furthermore, you're forgetting that turbo engines need completely different fuel injection timing maps.

This fuel injector tuning, particularly popular in the USA, from Automatik-ALH, even with the 0.184 injectors, can increase power by up to 36% compared to the 66kW version. Despite this, the engine runs cleanly.
A turbocharged ALH engine, properly tuned, should run smoothly without any issues.

CU.

ulf wrote:

faz wrote: M47-BMW 4000 RPM, 214.9 Nm torque, soot level 3.6, lambda 1.45, compared to a soot level of 1.6 at lambda 1.83. As you can see, the soot formation triples rapidly above a lambda value of 1.5. Bitte gib mir den deutschen Text, den du übersetzt haben möchtest. In addition, please provide the full load curve for the AGR engine from VAG . Wow, the BMW has 80% more soot content compared to the AGR with the VP 37.

"Personally, I believe that the soot values from what is likely the "original" VAG diagram (according to Rainer Quelle: MTZ 57/1996) have been somewhat "modified." It's not that BMW engines actually produce significantly more soot in practice. At least, I haven't noticed anything like that."

@ Cowmadness

"The automatic ALH, in my opinion, even has smaller injectors. Doesn't the manual ALH have 0.185 injectors? While the manual ALH has a 10mm pump plunger, the automatic ALH has an 11mm pump plunger, which means it must have smaller injectors. This also explains the overall greater power output. The same thing would likely happen if you were to retrofit an automatic ESP to a manual ALH with 0.205 injectors... or simply install the 11mm pump head."

As I mentioned, I'm using 0.205 nozzles in my manual transmission car, and I'm seeing a little bit of black smoke in the headlights behind me at night. Since everything else seems to be fine, I'm just attributing it to the agricultural diesel fuel (NOT heating oil!) that I'm using. I've heard before that the quality of agricultural diesel isn't always the best.

The automatic ALH, in my opinion, even has smaller injectors. Doesn't the manual ALH have 0.185 injectors? While the manual ALH has a 10mm pump plunger, the automatic ALH has an 11mm pump plunger, and therefore must have smaller injectors. This also explains the overall greater power output.

Okay. The automatic system has an 11mm pump and uses 0.158mm nozzles. Converting to 0.184mm nozzles results in approximately 36% more nozzle area.


The same thing is likely to happen if you install an automatic ESP system on an ALH engine that already has 0.205 injectors, or if you simply install the 11mm pump head.


Not quite, because in that case, the engine would be located just across the Russian border. Increasing the fuel injection amount would then be TOO excessive.

CU.

To minimize turbo lag, I need to ensure a large exhaust gas flow as quickly as possible. In this operating condition, this is only possible by initially running the engine with a slightly rich fuel mixture. If the engine is operated exactly at the soot limit, it will become sluggish and react slowly to driver inputs.
This phenomenon is familiar to many Euro-4 vehicle owners.


It's not just Euro 4 drivers (although it's particularly noticeable there). Even with the Euro 3 PD TDI, the response isn't as direct as with the VP TDI.

Best regards, WarLord.