AU missed with a turbidity value of 4.2 1/m...

Hello,
I completely missed the target: Haze value: 4.2 1/m, Bandwidth: 1.13 1/m.
I suspect that my very fuel-efficient, low-speed driving style, which I've maintained for several years,
so that a large amount of soot had accumulated in the exhaust.

This had already become apparent two years ago during the initial testing, with a relatively poor Throughput (Tr.) value of approximately 1.4 1/m and a Throughput bandwidth of 0.4 1/m (although it was still below the threshold). Limit of 2.0 1/m).
'When I replaced the middle muffler two years ago, a lot of soot came out of the old muffler - even then, I was driving very low-rev/fuel-efficient.'

I already kept the engine running at a very high RPM during the 30-minute drive to the inspection station: between 3000 and 4500 RPM. However, it apparently didn't have much of an effect anymore, as you can see from the turbidity value mentioned above.


Given that the reading is so far off, I'm wondering if full-throttle bursts on the highway are enough to clear the exhaust system, or if I should remove the two rear mufflers, verschandeln out the soot, and possibly blow it out with compressed air.

Thank you.

No way.

Get on the track, and floor it for a few kilometers.

You didn't write how many kilometers the vehicle has been driven.
Nozzles are wear parts, you know that!

m;

Edit: It also depends on *how* the examiner approaches the situation. The faster, the more Russian.

Hello,

I'm feeling guilty because I didn't mention that the odometer recently rolled over (to 299,999 km) – now I've driven about 7,000 km, so the total mileage is now approximately 307,000 km.

Since I know how expensive new nozzles are, I initially hoped that it wasn't something like that.
Could it be that the injectors are faulty if the fuel consumption is 4.4-4.7 liters per 100 kilometers?
greetings broesel

Is the EGR valve possibly stuck?

m;

I don't know, but I could definitely imagine it working well with my relaxed driving style.
I need to figure out how to check this temporarily (my VAG-COM gave me problems last time).
Greetings, broesel.

broesel wrote:

(Could the EGR valve possibly be stuck?) I don't know, but I could very well imagine it working well with my relaxed driving style.

Hi,

With a consistently low-revving driving style, the AGR valve actually remains in motion quite well, as the engine load is often relatively high due to the required torque.
Therefore, a large amount of fresh air is needed in the cylinders, and the amount of exhaust gases is low. Consequently, the EGR system is almost completely closed with each acceleration, and reopens when the vehicle is rolling.

Interestingly, you achieve the highest average air-fuel ratio (AFR) readings when you keep the engine running at minimal load, up to around 2500 rpm, and constantly drive around without shifting gears.

Quote:

Since the value is so completely wrong, I wonder if full-throttle bursts on the highway are enough to clear the exhaust system, or if I should remove the two rear mufflers, verschandeln out the soot, and possibly finally blow it out with compressed air?

If the maximum exhaust flow rate is sufficient to power the auxiliary power unit (APU) with a power output of 10kW or more, I suspect that in terms of exhaust venting, every workshop compressor could be replaced by just two full-throttle accelerations in 4th gear. The range up to ~4200 rpm can be replaced .

dieselmartin wrote the following:
It also depends on *how* the examiner approaches the situation. The faster, the more Russian.
I think this probably refers to the 'resolution' mentioned in the AU report. I mean 'time (in seconds)'!
'Funny enough, the descriptions are...' Time-values of the completed Acceptance Unit (AU) test 2 years ago were approximately 0.9 seconds.
The values for the current missed AU are between 1.7 and 1.8 seconds.

@ ulf:
regarding AGR:
It sounds like a stuck EGR valve is unlikely given my driving style.

regarding Disassembly of exhaust mufflers:
The better it would be if the full-power bursts were improved: I could save myself the hassle and mess of installation and removal in the garage!

I will heed your advice (except for the 'nozzles' part) and then report back after another attempt with the AU software!
Thanks - greetings from broesel.

broesel wrote:

Quote: dieselmartin wrote the following: It also depends on *how* the examiner approaches the situation. The faster, the more Russian. I think this probably refers to the "resolution" mentioned in the AU report. I mean "time (in seconds)"! "Funny enough, the descriptions are..." Time-values of the completed Acceptance Unit (AU) test 2 years ago were approximately 0.9 seconds. The values for the current missed AU are between 1.7 and 1.8 seconds.

The specifications. Zeit, as far as I know, indicates how long the engine takes to reach the target speed from a cold start, not how quickly the inspector presses the accelerator pedal.

However, longer times can naturally be caused by a more gentle use of the accelerator.

Quote:

The better it is if full-throttle bursts were improved: I could save myself the hassle and mess of installation and removal in the garage!

"Full-throttle bursts while stationary probably aren't enough; the engine needs to run with full throttle for a few seconds -> so full throttle on the road, exceeding 4000 rpm."

Quote:

I will heed your advice (except for the "dusen" part) and then report back after another AU attempt!

After x attempts, the total cost of all re-checks is higher than the price of a set of new nozzles.

After x attempts, the total cost of all re-checks is higher than the price of a set of new nozzles.
I specifically asked the TÜV inspector, and he said that the initial re-inspection for the environmental test (AU) doesn't cost anything extra, but the TÜV re-inspection does. Of course, I don't know how often they offer the AU re-inspection. But I'm going to indulge in that one thing, especially since the TÜV inspector also suggested the idea of getting it professionally cleaned.
greetings broesel

broesel wrote:

I specifically asked the TÜV inspector: he said that the re-test for the exhaust emissions (AU) initially costs nothing extra, but the TÜV re-test does. . .

Well, if that's actually stated in the TÜV fee regulations (?), then the people who created it probably completely overlooked a potential way to exploit the system -> I find that extremely hard to believe.
What a (rarely) compassionate healthcare professional might do in a specific case is, of course, a different matter.

I already paid back the amount I received from the sickness benefit back then. In that regard, I completely agree with Ulf. Nothing is free with them.

But what's the point? A friend knows a mechanic who has a workshop, and... well, at least the trip there is cheaper than buying new injectors.

I also experienced that the second time I applied for parental leave, it was for nothing. Even among the 'Reds,' who initially offered good, affordable, and competent service, there's been a growing trend towards shoddy workmanship and exploitation.

I had an AFN (air-fuel nitrogen) test done on my car with approximately 200,000 kilometers. My driving style is mostly aggressive, with full acceleration, frequent braking, or letting the car roll. When I accelerate, I do it fully, and when I'm on the highway, I try to go as fast as possible. The vehicle was driven on the highway for 70% of the time.

However, I failed the AU exam! What I didn't know before was that my ZKD (presumably a specific exam or module) was broken. I just burned off very small, barely visible amounts of coolant.
He passed the exam with flying colors.

In another instance, I interviewed an A6 2.5l VP-TDI driver who had just completed an emissions test. According to him, he almost exclusively drove his car for distances of less than 2000 kilometers, and almost exclusively in the city. According to what he told me, his last highway trip was about 8 weeks ago, but it was only partially loaded and covered a total distance of just 50 kilometers.

Anyway, this car with over 150,000 kilometers on the odometer produced a really nasty cloud of smoke during the emissions test. It didn't look that bad compared to my car, which failed the test. Surprisingly, this gentleman passed the exam!

Therefore, my assumption is that even a developing cylinder head gasket (ZKD) failure can be responsible for causing engine misfires.

I also once had problems with the emissions test (AU) on my old 1Z engine. During the AU test at approximately 150,000 km, I always had values of just under 3/m. When the TÜV inspector then asked me about the air filter ... well, I tried two more times without the air filter, and it worked. Two years later, at approximately 230,000 km, I had driven a few kilometers on the highway in a hurry, and I installed a new air filter right before the AU test, which resulted in values around 1/m and I passed the test on the first try. Everything, of course, with the same nozzles, etc.

- Regarding the air filter: It's brand new in my case!
- Regarding the ZKD (water pump): I replaced it not too long ago, and since then, there has been no water leakage!

I have now addressed the list of defects identified by the TÜV (German technical inspection agency); I will probably go back again at the end of this week to have the inspection re-evaluated, including a re-check of the emissions test (which I already completed during a fast drive on the highway).
I will report back.
greetings broesel

Hello,

I have now passed the eye exam with a phenomenal turbidity value of 0.4 1/m .
(reminder: previously 4.2 1/m; limit value 2.0 1/m)!

The following is what I have changed:
1.) Several high-speed highway drives (using 4th and 5th gear, reaching approximately 180 km/h, which is close to the stated maximum speed of 178 km/h according to the vehicle's documentation; full throttle for 5-10 minutes each time). After that, on the way to the technical inspection center, I drove at high speeds, including several bursts of acceleration to around 120 km/h.
2.) The built-in diesel pre-filter was replaced with a tube-shaped filter. Fuel is now flowing freely, without any air bubbles.
(I had air bubbles because of the pre-filter)!
3.) I removed the air filter (but it was almost new).
4.) The exhaust was brushed and blown out from the back.

The AU re-inspection was charged at €0 by TÜV-Süd!
TÜV re-inspection for 9.6€.

Greetings and thanks to everyone, broesel.

I suspect a different TÜV inspector was involved. A bandwidth of 1.13, as you specified, is not acceptable. A requirement for passing the inspection, in addition to the permissible average turbidity value, is a bandwidth of 0.5 or less (averaged over the last 3 measurements). This means that even with poor values, this bandwidth must be below 0.5. Usually, the turbidity values decrease from one gas emission to the next (as the exhaust gases are gradually expelled), and the values gradually approach a certain level (which reduces the bandwidth). Only these measurements are truly representative and largely eliminate the possibility of the inspector varying the gas pressure.
"Exceptions include, for example, sporadically occurring leaks from injection nozzles that exclude a bandwidth of less than 0.5 (but this is probably not the case in your example)."
The completion of the AU (acceptance test) with this large bandwidth, excluding the last example, indicates that the measured values still showed a strong tendency and had not yet approached the actual measured value. Normally, further measurements (gas injections) must be performed until the bandwidth is below 0.5 (the minimum number of gas injections is 4, the maximum number is at the discretion of the inspector). Only then is the measured value, regardless of whether it is too high or within the acceptable range, a representative value.