BMR Ladedruckproblem | Posts 32+

Hello,

Below 2000rpm, the lambda value is significantly higher than it should be. This is illogical.
Possible cause is poor fuel supply to the PD elements in that operating range (e.g., a small leak in the feed-return circuit) or, for example, a corrupted data set in the engine control unit.

Does the engine run within the specified RPM range with a limited fuel injection due to haze? Should he.

Intake size for fuel injection volume limitation due to haze is either the measured air mass value or the prevailing boost pressure. Suspect a limitation in the control unit regarding the charging pressure, perhaps the vacuum system is simply leaking, and the charger only builds up pressure later than it could?

Best regards, Rainer

Hello,
finally had the time and money to measure the pressure of the tandem pump (after another PPD element had failed), in order to:

dieselschrauber wrote:

Possible cause is poor fuel supply to the PD elements in that speed range (e.g., small leak in the forward/return circuit)

to rule out.
Result: 11 bar at 4000 1/min, Target value: 7.5 bar. For lower speeds, there is no specific RepLeitfaden.

Only as information... a log from a BMR after professional DPF cleaning.

Everything else is already written.

It took a while to finally get around to doing it, but now the DPF is new.
Resultat: No change in the problem. Low performance at low RPM and a boost pressure error around 2000 RPM under load.

Current Status: Fuel injectors inspected and two replaced a few months ago, intake manifold checked again today, intake valves are ok, and there is minimal play in the bearings, VTG rods are clear. I would be happy to re-press the underpressure system, but it was also sealed recently.

I'm planning to do another log flight tomorrow, but I don't really think the values will change much.


I'm really at a loss and therefore, I would really appreciate some more input. Should I try a different engine control unit?



Best regards

Here is the measurement.

4 years... ok...

Why don't you just check if the VTG is properly secured?
There is indeed a setting for the load control regulation that puts it in a completely on/off state. Then you can see if the shovels are being pulled in correctly.

Pressing the vacuum system with overpressure is also not a good idea... it can have different effects depending on the leak.

Just observe how the VTG switches from "on" to "off" in the basic settings mode, and possibly also measure the vacuum if it takes longer than 0.5 seconds to switch to the "on" position.

dieselschrauber wrote:

4 years... ok...

One always had either no time or no money

"Von Auf/Zu" still remains faster than 0.5 seconds. Here is the translation:

{TEXT}
Don't you see in the log that the value of "Position - Load Pressure Adjuster" has reached its maximum (over a long period and regardless of speed), yet the load pressure is not increasing?

Shouldn't I be asking myself why the charging pressure control is still adjusting, even though there is a significant difference in the control? I'm just assuming that it's a closed-loop control system. If not, the question is of course irrelevant.


With a vacuum system, I mean to press with a vacuum. So, "pull out". No loss can be determined.

Check the vacuum level, as there are often leaks in other components or valves that only intermittently cause the vacuum level to drop.

This regulation is not just a simple regulation; it works with pre-control. It estimates the charging pressure at time x and then controls the VTG accordingly beforehand. The pneumatic control of the VTG and the speed adjustment of the turbine are relatively slow, therefore so.

dieselschrauber wrote:

Check vacuum

I have. Also when operating each valve individually. Negative pressure remains stable.

If the position of the fuel pressure regulator is correct, why suspect a problem with the vacuum?

Quote:

The pressure remains stable.

Which value?

Quote:

If the position of the lift pump pressure sensor is correct, why suspect a problem with the vacuum?

It's difficult to see with the naked eye whether a switch has occurred between two positions or between the two Endpositions.

Are you sure that both attacks will be successful?

In the measurement values, there is no "target value/actual value" comparison for the position, according to my opinion.

Autoservice wrote:

A log of a BMR after professional DPF cleaning.

It seems that the "professional cleaning" of the DPF was not as professional as I had hoped.

Here, a pressure difference of over 400 mbar is still being measured at the DPF. With a target value of max 300 mbar.

dieselschrauber wrote:

The pressure remains stable. Quote: Which value?

60 cmHg on the gauge, which corresponds to approximately 0.8 bar.

dieselschrauber wrote:

Are you sure that both attacks will be successful? In the measurement values, there doesn't seem to be a "target value/actual value" comparison.

As I understand it from the log, 85% represents the upper limit.


The DPF is new. It is a replica made by Henkel. Where does this target value come from?

Hi

The vacuum is okay and should hopefully remain stable. Your engine likely doesn't have pneumatically operated intake valve flaps, which is a less common source of vacuum loss.
As always, it's best to clarify, I can't see your engine.

phgraf wrote:

dieselschrauber wrote: Are you sure that both attacks will be successful? In the measurement values, there doesn't seem to be a "target value/actual value" comparison. As I understand it from the log, 85% is the upper limit.

The path of the VTG bar is approximately 1cm, and the end positions may be burnt or not reached for other reasons, therefore, I would check to see if the mechanical stops are actually being reached.

phgraf wrote:

The DPF is new. It is a copy made by the company Henkel. Where does this target value come from?

400mbar at full throttle with a new DPF is actually quite high, and I suspect it's too much.

Why:
/viewtopic.php?t=24222
That's why.

Hi, Rainer

So, let's open the turbo and verschandeln it? Because the correct position can't be seen from the outside. It moves, but only about 1 cm.

I'm familiar with the thread, but since there's only one measurement from someone with the same engine, I was a bit taken aback by the absolute statement. Yes, it only had ~340,000 miles at 130,000 km, so I can certainly see that I was probably sold a lemon.
I also don't know how much soot was present in my measurement.
I could try using a downpipe instead of the DPF

dieselschrauber wrote:

The vacuum is okay and should hopefully remain stable. Your engine probably doesn't have pneumatically operated intake valves

. However, I replaced the intake, but not the intake valves themselves.

What do you expect to gain by disassembling the turbo instead of checking if the end positions are reached?

Does it really need an instruction manual?

phgraf wrote:

I'm familiar with the thread, but it only contains a single measurement from someone with the same engine as mine, which is why I was a bit taken aback by the absolute statement.

It doesn't have to be the exact same engine. It's about engines from the same generation. For engines with higher flow rates, a different exhaust system is naturally used, which has a larger diameter and thus also ensures a maximum of 300 mbar.
However, I am only aware of this specific limit. (Of course, there could also be other limits, but I haven't read about them here yet.) And this limit should actually only appear when the DPF is slowly becoming full. Certainly not with a new DPF like yours.

What you could also check: Does the car still have anything between the differential pressure sensors? A NOX storage container or something else that could be defective and cause high back pressure? Or is the hose side "behind the DPF" really sealed? If the hose were disconnected, then it would naturally measure too much differential pressure.

phgraf wrote:

But I also don't know how much soot was in my measurement.

Then just go ahead and revise and check it directly afterwards.