Hubraumvergrößerung bei BDH Motor möglich? | Posts 16+

Quote:

The testing device from the friendly company was only recalibrated a week ago.

Based on my experience, users of such and other tools often need "calibration" much more frequently. That being said, in practice, it doesn't really matter whether the device measures 30 bar, 31 bar, or 29 bar, as long as the measurements provide reproducible results.

The fact is:
- The values from the compression measurement are "strange." The reason for this can only be speculated upon.
- The values obtained from the idle speed control system do not match the compression measurement.

"When I see the amount of misinformation online about even the simplest tools, and how people should have been able to figure things out simply by reading the instructions (or even just thinking about it), it drives me crazy. That's why I'm very cautious when evaluating such measurements, especially if I don't know anything about the person who conducted them."

Given a properly performed compression test and a functioning device, I still consider issues with the valve timing (e.g., camshafts or hydraulic lifters) to be the most likely cause of the measured pressure values.
However, if the engine is running smoothly and not exhibiting any problems, I would only remove the cylinder head cover to check if the camshafts are in good condition.

@amishorty: Why are you taking so long? You're removing the cylinder head, checking the camshafts and valve actuators, as well as the lifters. Just the time spent on the compression tests alone would have been enough to remove the cylinder head covers.
Alles ok? Weiterfahren. Defekt? Repair...

And: By removing and reinstalling, the nozzle seals to the combustion chamber will certainly not get any better. Were new copper sealing rings even installed? I doubt it...
Or were the compression measurements taken through the glow plug openings? That would be too dangerous for me, as someone who works in a workshop. Removing a glow plug, big problem... }

Best regards, Rainer.

Thank you, Rainer, for your assessment.
"The accuracy of measurements taken with the devices (assuming the devices are in perfect working order) is always limited by the skill of the person using them, and you are absolutely right about that. My suspicion now also lies in the area of valve control. I think that cylinders 1 and 5 simply didn't receive enough air during the measurement because the valve opening was too small. I can't imagine such significant wear on cylinders 1 and 5."
The measurement was taken through the glow plug opening. Beforehand, I was asked whether the glow plugs could be easily unscrewed. Since I had removed them before, I was able to confirm that.
Today, I'm going to perform a LLRR measurement, then check the NW (although I would also prefer to do a separate lift test, but I don't know the valve lift values). Finally, I will replace the hydraulic lifters and rocker arms.
Following this, there should be a significant improvement in the filling of the aforementioned cylinders. The hydraulic components and levers have already accumulated a high mileage (366,000 km), so a replacement wouldn't hurt.
If any further damage appears, I will post about it here.

Best regards,
Michi

Quote:

Before that, I was asked whether the spark plugs were easy to unscrew.

Since I had already removed them once, I could of course confirm that.
}

Okay, first, let's check under the valve cover. Don't start replacing anything yet. You don't need to take any measurements right now. Since you have two cylinders that are misfiring, there should be a visible difference between them. Then, we need to figure out what's damaged. I'm guessing it's the camshaft. It's also clear that the hydraulic lifters and everything else in the engine isn't fresh anymore.

Here's a log of the LLRR activity from this afternoon.

This isn't a log... these are just a few values for a moment. What about cylinder 2? Did it not want to participate?

Possibly, cylinder 2 of the engine is the reference point (0 mg/H), but otherwise, the values are unremarkable.

Best regards, Rainer.

@matthias
Okay, here's the translation:

"Then, if you could, please explain what a log is. How long does a recording have to be in order to be called a log?"
And as Rainer already mentioned, the needle valve lifter is located in the nozzle of the second cylinder. That's why it didn't "work."
As far as I recall, this is the zero-point limit. All other cylinders should operate within this range, and the deviation should not be greater than ±1.5 mg per cycle.

I would still like an explanation.
This zero-value limit certainly also has a certain delivery volume. That volume is not 0, but has some fixed value, for example, 1.2mg per dose.
What happens if the zero-point shifts in the positive or negative direction? It's impossible to determine this, because the nozzle value with the NHG (Nullwertgrenze) is always the value at the zero-point, and that value isn't displayed.
If the zero-value threshold now shifts to the +/- range of, say, 15.0 mg/dose, for whatever reason, then you can only recognize this by the fact that all the other 5 values are moving +/- 1.5 mg/dose above or below 15.0 mg/dose.

Is this the right way to think about it, or am I making a mistake?

Thank you for reading.

Best regards,
Michi

Quote:

If the zero-value limit now shifts into the plus/minus range of, say, 15.0 mg/dose, for whatever reason, then you can only recognize this by the fact that all the other 5 values are moving plus/minus 1.5 mg/dose above or below 15.0 mg/dose. Is this the right way to think about it, or is it a mistake?

A cylinder requires, let's say, 5mg/hour of fuel at idle with a warm engine.
If a value of .0 mg/H is set for a specific cylinder in the idle speed control, then 6 mg/H is actually injected. The injection quantity value in measurement block 1 represents the average injection quantity across all cylinders.

A log of the idle speed control system makes sense if the values change significantly over time (which would be unusual). This cannot be determined from a snapshot. You saved a snapshot, not a log.
Minor variations in the compensation amounts or a slow "warm-up" process when starting the engine, on the other hand, are not uncommon.

Best regards, Rainer.

Quote:

If the zero-value limit now shifts into the plus/minus range of, say, 15.0 mg/dose, for whatever reason, then you can only recognize this by the fact that all the other 5 values are moving plus/minus 1.5 mg/dose above or below 15.0 mg/dose.

The term "zero-value limit" is poorly chosen. The idle speed control system ensures that, by adjusting the injection quantities for each individual cylinder, the engine runs smoothly at the required idle speed throughout all working cycles (720° crankshaft rotation). The engine control unit (ECU) for this engine with variable valve timing (VEP) displays the correction values relative to the reference cylinder, which in this case is cylinder No. 2. If a cylinder increases its injection quantity to maintain the speed (due to, for example, lower compression or a faulty injector), the injection quantities in the other cylinders are reduced accordingly to keep the idle speed constant. Conversely, if a cylinder performs better, the injection quantities are adjusted upwards.
Cylinder 2's deviation can only be observed indirectly, i.e., through changes in the electromagnetic emissions of the other cylinders and the average electromagnetic emission.
An extreme scenario for item number 2 would be if all other items showed significantly negative deviations greater than 2 mg/dose.
hg
Herbert.

Unfortunately, I only had time to complete both tests today. The results don't look too bad.
Since I had never seen the inside of a BDH engine before, I was initially surprised by the offset camshaft arrangement on both the intake and exhaust sides.
After taking a closer look, I have to say that the camshafts on cylinders 1 and 5, on the intake side, also have different amounts of material applied. This is also the case for the other cylinders. Since I don't have any new camshafts for comparison, I took some photos. I've attached them to the end of this post.

Three weeks ago, I had an oil pressure test done because the oil pump has now reached almost 377,000 km. However, the results were encouraging. The oil pressure was 1.3 bar at idle and 4.3 bar at 2000 rpm, which suggests that the pump is in good condition.

Regarding the LLRR (likely referring to a specific part or system), it should be noted that my knock sensor is located in the injector of the 3rd cylinder, even though it is registered as being associated with the 2nd cylinder. The 2nd cylinder is not being registered at all, which is strange, considering the knock sensor, as described above, is located in the injector of the 3rd cylinder. Can anyone explain this? The knock sensor was not installed incorrectly, because there is a crescent-shaped groove machined into the upper edge of the cylinder head, at the level of the 3rd cylinder. A crescent-shaped rubber piece with a hole for the knock sensor cable is inserted into this groove.

I'd like to get your opinion on the photos to see if everything looks okay.
The material of the intake camshaft on cylinder number 1 appears too thin to me.

Here are the photos:

Quote:

Regarding the LLRR, it should be noted that my knock sensor is located in the injector of the 3rd cylinder, even though it is registered as being in the 2nd cylinder. The 2nd cylinder is not displayed, which is strange, since the knock sensor, as described above, is located in the injector of the 3rd cylinder. Can anyone explain this to me?

The injection start control (which is the function of the needle lift control) and the idle rough running control are unrelated. In theory, any cylinder could be used as a reference for the idle rough running control.

Best regards, Rainer.

Hi,

was machen die Hydrostößel am 1. ZCylinder?
They could also be the reason why the intake valves aren't opening fully, which would result in low compression.

Do I have a problem with the optics, or does this cam look strange, and is it actually a problem? Is the image just showing it at an unfavorable angle, or is there some kind of discoloration? Which cylinder is this again?

Best regards, Rainer.

@ VW mechanics
I don't know yet. I haven't unpacked them yet, but they're all new anyway.

@ Rainer
Yes, it looks very strange. That's the intake side of the third cylinder. However, I don't think it's an optical illusion.
I visited the mechanic three days ago. He chimed in with his opinion. He said, "Everything looks fine," but he suggested, "You should replace the hydraulic fluids based on the mileage." I already knew that. But they don't really look closely at things.
I'll probably have to replace all the valves and the hydraulic lifters, as well as the rocker arms.
I'm just missing the waves.

I do have one more question, though:
I haven't ever looked under the VDs (presumably referring to valve deactivators) on V6 TDIs before, as this is my first diesel engine. But what I saw under there is completely unfamiliar to me.
Why was the valve mechanism designed to be so complex?
That's completely abnormal.
But the designers could have made it simpler, couldn't they?
I noticed that the roller rocker arms are not arranged side by side, but diagonally offset. In addition, the cams on the shafts are also offset, but more so than the arrangement of the roller rocker arms. It's about a 90-degree cam offset. Isn't that a bit much? To me, it looks like the valves are not opening in parallel, but with a slight delay, so that a larger overall opening time is achieved.
Well, and what about the waves? Those aren't cam lobes to me; they look more like sheet metal pipes with bulges and attached ring lobes. It's a really cheap design.
Why did they do it that way?

Because it's expensive, a solid material would be cheaper.