Idle Speed Tuning: Legality and Emissions Testing

Hello everyone,

In another thread, we were discussing as a side note how adjusting the idle speed (i.e., lowering it to 800 or less) can reduce fuel consumption and, like Julian mentioned, make the vehicle more suitable for parking garages.

What about the legality of such modifications? Does the target idle speed (see the specified data in the technical articles) fall under the approval certificate (ABE) for the car, or does it not matter at all?

How about the emissions test? I vaguely remember that the idle speed was important for gasoline engines, but I haven't had an emissions test yet with my TDI.

I understand that they can usually be corrected quickly before the deadline.

Best regards,

Jan.

Hi Jan,

I can't comment on the legality, but I don't think anyone will make a big deal out of it.

Regarding the automatic update: Yes, the LL (likely referring to a specific parameter or setting) speed is included. There's a range within which the LL must be, otherwise the computer won't perform the automatic update.

"With my Golf 2, the inspector also regularly had to adjust the idle speed before the measurement could begin (it was easy to do with a screwdriver)."

During my vehicle inspection (HU) and emissions test (AU), I also brought along my laptop and interface - just in case they had something to complain about and said "VW needs to adjust this" (I had cleverly hidden the 10-cent adapter behind the ABS unit , because with my colleague's Ibiza ASV, the inspector checked the pump connector like crazy ).

m;

Hi Martin,

What exactly are they measuring during a diesel emissions test? How do they determine the idle speed and the maximum engine speed?

I highly doubt they're using the diagnostic monitoring system for that, and they certainly won't be plugging anything into the diagnostic interface, will they?

What other things are you planning to implement (main interest: Do you have your own temperature sensor for the engine that replaces the dipstick? Because it wouldn't be easy for me to do that).

I'll probably set the LL to the optimal value for the AU, assuming I've managed to fine-tune it by then.

Best regards,

Jan.

My Diesel AUs - a short report

The dipstick is removed, and a temperature sensor with adjustable length is inserted.
The oil must be at least 80 degrees.

During the inspection, the inspector only connected 2 terminals to the battery (they determine the engine speed based on the residual ripple).

On the D (Golf 2 JP), they sometimes still have a strain gauge clipped onto an injector line (but I ruined that fun for them with the large AFN cover on the 1Z ).

Then the tractor idles in the low gear (LL) -> we measure the LL engine speed.

After that, the gas is slowly increased until either nothing more comes out (we have reached the maximum speed) or the tractor explodes . Oops, it seems it didn't regulate itself (this has never happened before).
My heart stopped for as long as the engine was running at full speed.

Then comes the first measurement: Full throttle from idle (LL) for approximately 1.2 seconds, followed by holding full throttle for 3 seconds (or so).
(but the K-value is discarded).

Next, three more measurements will be taken, and the average of their K-values will be calculated.

If you emit less than 2.0 grams of pollutants, you get a sticker; otherwise, you don't.

m;

Hi,

Okay, that's good to know. Then I need to figure out a way to store my sensor probe (a place to put it), because it's best not to remove it, or at least, they shouldn't be removing it.

Best regards,

Jan.

In my previous diesel engine overhauls (at two different companies), the oil temperature was never measured.

At a company, a "electronic sensor" was attached to the engine block (I believe it was magnetically attached) to record speed and temperature. However, this sensor could only measure the block temperature, not the oil temperature.

In the second test, only the battery was connected (RPM monitoring was achieved through harmonic analysis). The device only queried via the control panel at startup whether the oil temperature would exceed 80°C. The inspector simply confirmed this with "Yes"...

I would just call the workshop where you want the test done and ask them how they measure it. Most places don't take it too seriously anyway, and if needed, they would probably hold the sensor against any other suitable, temperature-controlled location, if you wish.

Regards,
Guste.

Hi,

...or should I rely on it if my display shows a temperature of over 80 degrees?

Because one thing is certain: When I'm driving in automatic mode, I make sure the engine is properly warmed up... no one is allowed to floor it when the engine is cold.

Best regards,

Jan.

I can also tell you stories...

Unfortunately, at AU, nothing has improved in terms of engine protection for years.
Whether I drove my Golf 2 1.6 D, manufactured in 1985, or my current Golf 3 TDI for the emissions test, it's always the same story: pure engine abuse!!!

I've worked at at least 6 different companies, and the process is always the same.
To determine the engine speed, the battery is tapped, and the engine oil temperature is measured using a sensor inserted into the guide tube of the dipstick.

And now, let the chaos begin...
Three full-throttle acceleration tests are performed sequentially. The testing computer instructs the inspector on when and for how long to apply full throttle. During these tests, a turbidity value is measured, and an arithmetic mean is calculated. If this value is below the maximum threshold, the inspection sticker is issued, and the test is passed.

The last time I went for the technical inspection (TÜV NORD), I made sure to warm up the engine thoroughly, even giving it a bit of a push on the highway to clear out the turbo and exhaust system. When I arrived at the TÜV with the engine warm, there was a really long line of cars waiting at the gates. It was a very cold day, and the engine had already cooled down to lukewarm after about half an hour. Since there were still a few cars in front of me, I wanted to bring the engine back up to operating temperature while idling, because I didn't want them to test it when it was cold.
After a few minutes, a very stressed-looking inspector came and told me to drive the car into the inspection area because there were still some disagreements with the TÜV (technical inspection authority). I left the car with him, and he started working on it. As always, I stayed and watched.
The oil temperature was around 55°C, but that idiot found a way to get the engine up to temperature. He put in earplugs and slammed the accelerator pedal to the floor...

Oh dear, oh dear.
After about a minute of this ordeal, I asked him what was going on, since the measurement wasn't working. The answer was: 'I have to get the engine up to temperature first, and quickly. Or do you want to pay for my extra hour of work as well??? '
After another 3 minutes of full throttle, the oil temperature exceeded 80°C, and he began the measurements. After 3 full-throttle accelerations, it was finally over, and the approval sticker was granted.

The moral of the story:
The engine loses a significant amount of resources during every inspection (AU). None of us stress the engine as much as the AU does.
So, make sure to drive there with the engine properly warmed up, and if possible, with fresh oil.
Your beloved TDI cars will thank you for it...

Hi Georg,

I think I'd be so cheeky now that I would snatch the inspector's car and drive away from the premises without paying, and wait for a letter from their lawyer.

After that, a pleasant legal dispute would ensue, which is guaranteed to be cheaper than a new 1Z!

Normally, I'm friendly to Klingons of all types (VW, TÜV, etc.), even when they're talking nonsense ("Servooil gets hot and contracts!!! A MASTER said so!!!"), but if they're doing something wrong, I'll step in if I'm present.

Just because I commissioned a service doesn't mean I've forfeited all rights to my property!

m;

I also caused a little bit of trouble. Okay, not enough to involve a lawyer.

The local manager was unable/unwilling to speak with me immediately, so I wrote a formal complaint. And as you know, I only write very short essays!

After two weeks, a letter arrived. No apology, no, but a reminder!!!

After a few lines of blah blah, I was told that I had narrowly avoided a fine. Apparently, it is forbidden to warm up the engine while idling without driving, which has been confirmed by the Federal Ministry and leading automobile manufacturers. And in that vein, it went on and on...
... Ultimately, the AU testing procedure was developed in collaboration with automotive manufacturers and has no negative impact on the engine.

Following that, I sent another, even more strongly worded letter (5 pages long, with legal and manufacturer references), and I put 'Dipl.-Ing.' before my name.

After another 3 weeks, an apology arrived, stating that the incident was due to a misunderstanding on the part of the TÜV employee.

I wasn't going to let it go, and... No, not a lawyer!
I sent the entire story to ADAC for publication.
And what do you think?
No, they weren't interested in the story.
Since I was also disappointed by our beloved automobile club, I decided to give up and not waste a few years of my stress-free life.

Because, even a lawyer can only extend my life on paper...

Wow, that's an amazing story.

So far, I've only had angels working at the TÜV (technical inspection agency)!

My first Golf, a 2er model, was fortunately passed the emissions test by the inspector, because it depends extremely on _how_ the inspector accelerates the car. And that's not mentioned in the report .

After the first 2.5, he simply moved his foot "differently," and I was 1.5 above it .

Unfortunately, 4 days later, the head gasket blew, and half a year later, there was nothing left with any compression .

But even the first (homemade) TÜV inspection with my TDI was pleasant (maybe the Klingons were in a good mood because I had the passenger seat completely filled with Bosch literature ).

They were definitely very nice and reasonably competent when they spoke to me, and they didn't just silently and grumpily work on my car.

m;