Log File Analysis: Insights & Optimization

Hello! I'm just starting to use VAG-Com for logging. I've found a lot of information about the topic here.
I've read about it, but I'm not quite clear on the analysis. I want to check my LMM (Mass Air Flow Sensor), boost pressure, etc., to make sure everything is okay, because my car (Golf3, 90PS, ALE, 245000Km) feels a bit "sluggish." Which groups should I log? I've read that for the LMM, the groups are 8/10/11. But how do you analyze it? Which other groups should be logged together? Would anyone of you like to take a look at the CSV files, or should I prepare them (how?)?
Can someone help me?

Best regards, B.C.

Hello, I've now created a log file for groups 8/10/11 and edited and translated it in Excel. Could someone please take a look at it? In particular, the values for "GRA limit" and "Magnet valve duty cycle" seem implausible to me!

Hi,

The label 'GRA Limit' in measurement block 8 is incorrect. Where did you get your labeling file from?
Regarding the duty cycle of the magnetic valve for turbocharger boost pressure control: it looks good.

Best regards, Rainer.

Hi Rainer!
Thank you for taking a look at this. I'm using VAG-Com 311.2 (in English). I copied the translation from a log file here on the forum to help me move forward. In that log, blocks 8/10/11 were also logged. I thought the labels might be correct... In the original, block 8 shows "Inj. Qty" three times. What do those mean?
What additional information needs to be logged in order to provide insights into potential defects?
As I said, it used to perform better. Are the values from the mass airflow sensor (MAF) okay, or are they too low?
My main problem is generally the interpretation of the values, because there aren't always target or expected values.
In VAG-Com, and in the case of the mass airflow sensor (MAF), the actual values should be higher than the target values, as I have read here.

Hi,

The values in measurement block 8 represent:
1. Speed (revolutions per minute)
2: Injection amount per injection, driver preference (in mg).
3: Injection amount, torque limitation, mg/stroke.
4: Injection quantity for smoke reduction (air mass dependent) - mg per injection.

It appears that these are quite normal values for a 90hp TDI engine.
The air quality isn't great, but as you can see from the limit, it's not critical.

If you choose the correct measurement block, you will also see a direct comparison of the desired air mass value and the actual measured value.

Best regards, Rainer.

Hi Rainer,
Thanks for the quick response! I'll take a closer look at it tomorrow.
Which blocks should I additionally log to monitor the system? I want to determine if everything is working correctly or if something needs repair.

Hi,

Actually, I would say the engine is okay if I look at your readings and the error memory is empty.
Don't forget to check simple things like air and diesel filters.

Just run some tests with KPower; the demo version is available for free download. Then you'll see if there's a lack of power and whether further investigation is needed. The download link is at the very bottom.
http://shop.dieselschrauber.de/product_info.php/products_id/53

Best regards, Rainer.

Hi!
Great tip, I didn't know there was a demo available . I'll try it tomorrow!
I replaced the diesel filter, air filter, and timing belt before getting it roadworthy again (it's my winter car). It was checked with TDI-graph software and meticulously adjusted. Well, it used to be a...
Company car that I bought from us with 216,000 km (approximately 135,000 miles). I drove it for one winter, and now it has 246,000 km (approximately 153,000 miles). The authorized workshop messed up a lot of things on this car (e.g., the timing belt was still too tight after 60,000 km), and I don't even know what work has already been done (like the mass airflow sensor, for example). I just noticed that it feels "sluggish." Now I want to determine whether the problem is due to engine wear or to all the potential faults.

Thank you!

Hi,

If any work has been done on the timing belt, it's also a good idea to check the valve timing.

Best regards, Rainer.

Hi,

"During the timing belt replacement, I paid very close attention to the markings on the crankshaft. I blocked the camshaft with a correctly sized wrench and also visually checked its position. Afterwards, I adjusted the injection timing using TDI-graf (it was too early with the old belt). How else can one check the valve timing?"
I've tried KPower (is that your software ? ). I simply used the existing log file that I uploaded. However, it shows a whopping 90.2 kW instead of horsepower! I will later try logging groups 5/6 as mentioned. Are there any guidelines for the driving routine during logging? For example, only one gear, going through the entire RPM range once, or just full throttle?

Hi,

Oh . I absolutely must implement a function that prevents any measurement from being taken without first reading the help documentation.
Just press F1 in Kpower or go to the help menu; everything is explained there. If you click on "something" without thinking, that's all you'll get.

Best regards, Rainer.

"P.S.: And if it says 'depress the clutch and let the vehicle roll down' during the procedure, does that mean you should keep the clutch depressed?"

OHH! I guess I messed up .
After reading the help file, I am still looking for a flat stretch of road with an appropriate length. Is it necessary to roll out with the clutch depressed until 0 km/h in order to obtain accurate measurements? This significantly extends the section of the route that must be flat. How inaccurate will the measurement be if logging stops during the rollout at approximately 60 km/h?

Hi, it's not necessary to decelerate all the way down to 0 km/h; usually, letting the vehicle roll down to about two-thirds of its maximum speed is sufficient. For example, if acceleration occurs up to 120 km/h in third gear, allowing the vehicle to coast down to 75 km/h is enough (the remaining values are interpolated by the program).

Best regards, Rainer.