# Measuring AFR with Vag-Com



## moogie (Jan 26, 2006)

Can anyone say if measuring AFR with Vag-com from Block 002 is considered to be accurate with the TFSI engines? Also, if anyone has done logging with the AFR Excel-sheet available from Ross-tech, please let me know what you used for the "adjustable constant". My values are still way off from what they would be in real life, however, just plotting them and looking at the differences gives a lot of info already.
The reason I am asking this, is that we did some logging yesterday from both my A3 and my friends A4, and according to these results, both would appear to be running very rich in the mid rpm area (upto 4000-4500rpm). We logged the graphs with both stock and tuned softwares, and atleast based on how the stock figures look, I'm guessing that the results could be quite accurate. I'm not going to post the results yet, not until I've been able to verify that they are correct.
Thanks!


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## [email protected] (Aug 25, 2001)

*Re: Measuring AFR with Vag-Com (moogie)*

"Very Rich" as in the mid 11s to high 10s??? If so that is correct, i would look at block 033 which shows actual vs. requested Lambda


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## moogie (Jan 26, 2006)

*Re: Measuring AFR with Vag-Com ([email protected])*

"Very rich" as in below 10 for my A3, and even the A4 was doing significantly righer than what the stock does at the same RPM. Please keep in mind that I am partially "guessing" these figures, because, as said, although I have the right scale in the graphs, the absolute numbers are not directly comparable to anything yet - not until I get the right value for the "adjustable constant".
What should I look for if I were to measure the Lambda values?


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## PD Performance (Jul 1, 2004)

*Re: Measuring AFR with Vag-Com (moogie)*


_Quote, originally posted by *moogie* »_Can anyone say if measuring AFR with Vag-com from Block 002 is considered to be accurate with the TFSI engines? Also, if anyone has done logging with the AFR Excel-sheet available from Ross-tech, please let me know what you used for the "adjustable constant". My values are still way off from what they would be in real life, however, just plotting them and looking at the differences gives a lot of info already.
The reason I am asking this, is that we did some logging yesterday from both my A3 and my friends A4, and according to these results, both would appear to be running very rich in the mid rpm area (upto 4000-4500rpm). We logged the graphs with both stock and tuned softwares, and atleast based on how the stock figures look, I'm guessing that the results could be quite accurate. I'm not going to post the results yet, not until I've been able to verify that they are correct.
Thanks!

Forget all that just use block 031.. Our cars have an actual wideband 02 sensor.. same one used in most of the aftermarket wideband meters now.
There will be 2 fields.. The first is showing actual readings. The second is showing what you are trying to attain.
You will have no problem trying to attain the requested A/F on these cars. 
The readings however will be in lambda..Basically a percent of stoic so you will need to calculate them back (until you remember some basic points to average from) to the ratio type AF people usually speak of.
So 1 lambda is 14.7:1 (stoic for a gasoline engine)
If you have 1.1 lambda you have roughly 16.2:1
IF you have .9 lambda you have 13.2:1
.8 is roughly 11.75:1
etc etc etc
When just cruising around you will notice that the second field stays at 1.00 most of the time. That is because for fuel economy, keeping the cat temp up, and emissions you want to stay near stoic. The actual reading in the first field will swing up and down from .9.. to 1.1 (can be more just an example) trying to maintain an average of 1.0


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## moogie (Jan 26, 2006)

*Re: Measuring AFR with Vag-Com (PD Performance)*


_Quote, originally posted by *PD Performance* »_Forget all that just use block 031.. Our cars have an actual wideband 02 sensor.. same one used in most of the aftermarket wideband meters now.

Thanks! I'll give this a try, lets see how the numbers compare to the block 002 results.


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## bhvrdr (Jan 26, 2005)

*Re: Measuring AFR with Vag-Com (moogie)*

Like Chris said, you'll get great results usine block 31. Not sure if this is helpful but...
http://www.mjbmotorsport.com/datalog.html
cheers! Mike


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## moogie (Jan 26, 2006)

*Re: Measuring AFR with Vag-Com (moogie)*

Block 031 seems to do the trick. Thanks all! http://****************.com/smile/emthup.gif Here's a chart of what the ratio looks like on my A3, just incase anyone is interested.


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## jmhart (Dec 28, 2005)

*Re: Measuring AFR with Vag-Com (moogie)*

This thread along with a recent somewhat heated thread involving some vendor posts regarding tuners other than APR running too lean and therefore risking decreased component longevity due to elevated pre-turbine EGTs inspired me to collect some data and generate a graph as well.
















The first run was after a leisurely cruise through town to get to the highway. The second was done within a few minutes of the first run. Interestingly, on the second run, the AF was significantly richer. Any theories why that might be? Temperature related perhaps?
In any case, these runs on GIAC X+ do not appear to be that much different from APR. Dare I say that previous claims of 'other tuners' running dangerously lean don't seem all that valid?










_Modified by jmhart at 7:04 PM 7-2-2006_


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## LeBlanc. (Jul 15, 2003)

*Re: Measuring AFR with Vag-Com (jmhart)*


_Quote, originally posted by *jmhart* »_ Any theories why that might be? Temperature related perhaps?
In any case, these runs on GIAC X+ do not appear to be that much different from APR. Dare I say that previous claims of 'other tuners' running dangerously lean don't seem all that valid?










I'd say IAT is the cause of the enrichment on the second run.
Your IC picked up some heat for sure.
Secondly, good point about the AFRs. That's probably why almost
every tuner out there basically makes the same amount of power.
They're all already close to maxing out the stock fuel pump, so it's
really a matter of how aggressive the timing is.


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