Vag-com logging question

[FourRings80]

Did a few vag-com measuring blocks today and something got my attention in my MAF logs. It seems abnormal to me that after releasing the gas the g/s could fall to 1,56 at 2920 rpm and at 5,5 g/s at 2360 rpm......could someone explain to me whats up? sign of a failing MAF?

Engine Speed Mass Air Flow
(G28) (G70)
/min g/s


2040 24,11
2120 35,03
2320 45,19
2560 59,39
2920 75,36
2920 1,56
2360 5,5
1840 4,92
1280 5,72
960 3,64
840 3,33
760 3,31
760 3,19
760 3,11
760 3,06


don't think this Is related:
Got a fault code 17522 (P1114) oxygen sensor B1S2 Internal resistance too high. ( Intermittent)

Thanks for any inputs, toughts or comments

[dougyfresh]

What are the commas for? Did you lift off the gas pedal at 3400rpm? Why so early? A good log would be in 3rd gear from 2000rpm up to about 5000rpm and your throttle position should be at 100% (wide open). There is some helpful VAG-Com logging info here: http://audizine.com/forum/showthread.php?t=43545

In the future: Two easy methods of posting up logs here are 1) via screen capture and post up that image, or 2) upload the csv file to google documents and share the document with the public and link it here.

Did a few vag-com measuring blocks today and something got my attention in my MAF logs. It seems abnormal to me that after releasing the gas the g/s could fall to 1,56 at 2920 rpm and at 5,5 g/s at 2360 rpm......could someone explain to me whats up? sign of a failing MAF?

To answer your question about why the MAF readings fall when you let off the accelerator...

You let off the gas pedal, the ECU registers this and closes the throttle plate. As a result of closing the throttle the engine is at idle (in regards to air and fuel). At idle the MAF readings are in the 2-3 g/sec range. If you were shifting gears this would happen for a split second (or how ever long it takes you to shift gears). If you were accelerating in gear but just let off the gas and let the engine decel on its own, then the logs would show this even though the rpm is up around 2900rpm and falling.

Does this make any sense? That is the easiest I can boil it down to without getting long-winded.

[FourRings80]

Ok thanks makes perfect sense, I think I posted the wrong log. But Is the modulating MAF reading normal, if I let off the gas and let the engine decel on its own? Shouldn't they be in the 3,xx g/s? I guess its normal...

Can't post up logs via screen capture for some reason. So I went on google documents like you suggested .

here's what I got:

http://http://spreadsheets.google.com/pub?key=pK4H3zHL8NQQoHV4lF9WZUg

[dougyfresh]

that is much better. good job . get rid of group 002 and add in group 020 to see correction factors on timing advance. why are you going to timing advance after top dead center (negative #s)? I'm not used to K03 timing advance curves. Just BT.


You can see at 6160rpm that throttle plate angle is down near nothing. You let off the gas pedal for a split second (shifted gears?). Hence the mass flow rate of 3g/sec

[FourRings80]

that is much better. good job . get rid of group 002 and add in group 020 to see correction factors on timing advance. why are you going to timing advance after top dead center (negative #s)? I'm not used to K03 timing advance curves. Just BT.


You can see at 6160rpm that throttle plate angle is down near nothing. You let off the gas pedal for a split second (shifted gears?). Hence the mass flow rate of 3g/sec

Yup shifted in 4th, I have no idea about the negative numbers? I'm no expert just someone who loves working on his car and wants to learn.

My engine is pinging under load... changed my plugs to BKRFE with a .032gap. I'm at a loss right now, so started logging only to find that I got a lot to learn .

Thanks for the help Dougyfresh

[dougyfresh]

My engine is pinging under load... changed my plugs to BKRFE with a .032gap. I'm at a loss right now, so started logging only to find that I got a lot to learn .

Pinging? That would explain the very low (almost non-existant) timing advance. Have you read through the GIAC Pinging thread? I am not familiar with what other APR 1+ users are using for spark plugs. Us BT guys have found the Bosch F5DPORs work well. That is what I am using but they are not cheap.

Log blocks 003 and 020. Block 020 will give you timing advance correction (otherwise known as 'CF' or correction factor). This is the amount of timing advance the ECU is pulling out of the built-in timing advance curve. It is a byproduct of what the knock sensors are feeding the ECU. Block 003 also gives you the actual timing advance so having that block active can help you correlate the two. If you are pinging then your CFs on block 020 must be pretty high.

Here is some reading on block 020 and what to look out for (scroll down): http://www.mjbmotorsport.com/datalog.html

Glad to have helped out in any form. Post up if you have any questions.

[FourRings80]

To my knowledge most APR 1+ users have OEM NGK PFR6Q (Iridium) or NGK BKR6E (coppers) or go with NGK BKR7E (copper 1 colder)
with gapping .028" or .030" or .032"

I'm running the NGK BKR7E's gapped at .032"
Got a few logs up: block 003 and block 020

http://spreadsheets.google.com/pub?k...NQT5CDDWF1f3SQ


I might give those plugs a try if I can't cure the pinging. I'll try to change them early next week and see if my logs get better.

[FourRings80]

I bought and installed new plugs, Bosch super FR5DTC ($7.09) each. I had to change my engine speed sensor also mine died today

so I pulled a few logs and the cars seems to be running a lot better and I did experience any ping at all .

http://spreadsheets.google.com/pub?k...NQRIfXTEjwCCbg