A quick and easy way to street tune your CSL conversion for drivability.

[karter16]

I went for another run this morning (about 5 degrees cooler than last night).

I didn't need to look at the log file to know that this is the right approach. Honestly was like driving the car with the MAP sensor enabled.

As you can see from the log there's still some tuning to go, mostly around the very low rpm range which is really hard to consistently hit while driving (especially with SMG). But essentially all the cells are pretty rapidly converging at 1.0 (those that still have some work to do are where they didn't have good coverage in the previous logging run).



I'm stoked. I'm very confident now that this is the trick to nailing down the low RPM, and just need some others to further validate what I'm seeing.

There are two key learnings out of this:

1: It is important to make sure the DME is actually functioning the way you think it is. In this case the assumption was that AQ_REL (Relative Opening) was used by the Alpha_N (VE) table the same as it is in the VANOS tables, etc. Digging into the disassembled code showed that this was not the case and that the Alpha_N (VE) table y-axis uses a modified form of AQ_REL at low RPM. The effect of this is that, if not corrected, MegaLogViewer attributes Lambda Integrator values to the wrong Relative Opening cell. This results in lower RF (relative fill) values being entered into the VE table, which in turn has the effect of making that cell leaner than it should be.

2: Disabling the MAP sensor is the second key to this process. The way the MAP sensor works is to compensate for the difference between the Alpha_N (VE) table calculated RF and the real-world RF calculated from the MAP sensor readings. This means that if the MAP Sensor is left enabled during this process it has the effect of covering up error in the Alpha_N (VE) table. With the MAP sensor enabled I had a pretty reasonable VE table, but with some areas that weren't quite right and seemed to keep moving around and couldn't quite be nailed down (the MAP sensor was masking inaccuracies). Disabling the MAP sensor takes that variable away and helps target a more accurate VE table more quickly.

[Bry5on]

I’m still not clear on why we need to do this correction. If we’re seeking a stoichiometric 1.0 number, then using only that multiplier to determine the cell in the fuel map, we should not be modifying the end result.

In the case that we do need to make this correction, that would mean that the DME is deliberately targeting a ‘lean’ mixture in throttle transients and using the O2 sensors to bring it back to stoich in steady state. Seems a little odd to me, logically.

edit: Nevermind, I see now! This is changing the actual throttle opening position, not the fueling amount. Makes sense. Leaving this here in case I was not the only one misinterpreting.

[karter16]

Okay cool, just making sure. Appreciate the references

Yeah absolutely - The more we constructively challenge each other's work the better - no one is immune to mistakes or misunderstandings, so we all benefit from robust discussion :-)


I did a test drive just now.

I took my most recent VE log (note this was first one with MAP sensor disabled which I think is why it shows slightly lean across the board - I think the MAP sensor was compensating for/hiding this) and ran it through the spreadsheet, then imported to MLV, then into your spreadsheet Heinz, to generate the new VE table. The result was as I was expecting, that the mismatched AQ_REL values were previously making low RPM appear richer than they actually were (e.g. more fuel was needed).



I then went for a (reasonably quick) run (about 6000 log lines) focusing on the low RPM and could tell the improvement pretty much immediately, no-throttle, low-rpm downshifts were particularly noticeable, rev matching was even better than previously, the car had even more pep than previously (remember I'm currently doing these runs with the MAP sensor turned off as well, so when I'm making these comparisons it's on pure AlphaN without the MAP sensor correcting anything).

And I think the MLV view speaks for itself - Lambda around the high change areas is significantly better, and a lot of values that were quite wrong are now spot on. There's those couple areas between 870 and 1100 RPM to clean up (that previously weren't clearly identifiable and kept moving around - which makes sense given AQ_REL was being misinterpreted) but all in all this is quite a lot of improvement for a single run, and it's very noticeable when driving.



I'll do another run tomorrow off the back of this to prove further that this converges on a neat end result, but I'm pretty confident from this first run that this is the missing trick to really nailing down the low RPM.

Important to note as well that I am running pure AlphaN with the MAP sensor disabled. I think this is really key when logging as well to not end up masking inaccuracies in the VE table.

[heinzboehmer]

Okay cool, just making sure. Appreciate the references

As for the sheet, I'll wait until it's validated by a few of us before making a copy.

[karter16]

Please note that I fixed a bug (typo in formula) just now. heinzboehmer if you took a copy of the sheet already then you'll want to grab the latest version.

[karter16]

Hell yeah, thank you!

I just have one dumb question that came to mind. The y axis on the VE table for CSL FW is AQ_REL_ALPHA_N and not AQ_REL, right?

Yessir

Line 14 (and line 17 for the warm-up table).



And here's the evidence (lines 38 to 43) that aq_rel_alpha_n is aq_rel modified by aq_rel_alpha_n_fakt (which in turn is lookup based on RPM from kf_aq_rel_alpha_n_fakt table)

[heinzboehmer]

Okay - I spun up some google sheets to handle the conversion of AQ_REL to AQ_REL_ALPHA_N in TestO logfiles in a somewhat general manner.

Hell yeah, thank you!

I just have one dumb question that came to mind. The y axis on the VE table for CSL FW is AQ_REL_ALPHA_N and not AQ_REL, right?

[karter16]

Okay - I spun up some google sheets to handle the conversion of AQ_REL to AQ_REL_ALPHA_N in TestO logfiles in a somewhat general manner.

- Read the instructions sheet first.
- It can take input log files with up to 26 variables and up to 100,000 rows. It doesn't matter what order the variables are in, so long as Relative Opening (relativer Oeffnungsquerschnitt) and RPM are present.
- The Calculations tab shows all the working to show exactly what it does.

https://docs.google.com/spreadsheets/d/1d4vk_oGeeSSSVz16fhjv68uoRAsH7UjmET_CeJ6chhQ/edit?usp=sharing

Import Raw logfile:



Copy of the ALPHA_N_FAKT table:



The Calculations:



And the output:



I will put this through its paces with my car, and would be great if some others can do so as well.

heinzboehmer once a few of us have tried this out and we are all comfortable with this it would be super awesome if you'd be happy to add these sheets to your file so that we can keep everything in one place (and I can remove the separate link above).

[karter16]

Wow, yeah, that's significant. Should probably incorporate that factor into the spreadsheet.

Coincidentally (or maybe not...), the parts of the map affected by AQ_REL_ALPHA_N_FAKT are where I most notice a drivability difference between stock and franken-CSL.

Have you gone out to do some rounds of VE tuning with the correction applied? Curious to see how noticeable the difference is. I'll give it a shot myself once my car is put back together (probably next week).

I haven't yet but I'm itching to as soon as I'm not busy with work.


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[karter16]

Is this just a fixed multiplier? If so, I suppose we can apply it directly on top of any given part throttle fuel tuning, no?

I did have to tune some of these regions with AFR so this would explain some of that!

The adjustment needs to be made to each line in the TestO log. Reason being that MegaLogViewer is summarizing that info.

Because the adjustment factor varies between 0.7 and 1.0 between 900 and 2400 rpm the raw Relative Opening data points need to be adjusted before the log is summarized by MLV.

At this point I'm envisaging an extra sheet in Heinz's spreadsheet where you import your log, it applies the linear interpolation for RO for each line, then you export the log file and open in MLV.

Only accurate alternative is to run a modified prog binary that sends AQ_REL_ALPHA_N over DS2. And for the casual user that's a lot more involved, so I think the log file correction approach is best for now.


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[Bry5on]

Is this just a fixed multiplier? If so, I suppose we can apply it directly on top of any given part throttle fuel tuning, no?

I did have to tune some of these regions with AFR so this would explain some of that!

[heinzboehmer]

And to visualize it better here is the difference:



It's important to remember here that a nominal value is 1.00. This means that a difference of 0.058 is significant. It's the difference between too lean (1.059) and bang on (1.002). This of course only affects 2400rpm and under, but the effect is not small, especially given this is prime low rpm, low throttle, drivability territory.

Wow, yeah, that's significant. Should probably incorporate that factor into the spreadsheet.

Coincidentally (or maybe not...), the parts of the map affected by AQ_REL_ALPHA_N_FAKT are where I most notice a drivability difference between stock and franken-CSL.

Have you gone out to do some rounds of VE tuning with the correction applied? Curious to see how noticeable the difference is. I'll give it a shot myself once my car is put back together (probably next week).

[karter16]

Okay so I've now conclusively confirmed that Relative Opening (AQ_REL) as logged in TestO is NOT the same as the Relative Opening value used in the AlphaN map. The AlphaN map uses a modified version of AQ_REL based on the kl_aq_rel_alpha_n_fakt table in my last post. I am calling this modified Relative Opening value AQ_REL_ALPHA_N.

To show that the effect that this has isn't purely academic I took a VE tuning log I captured a while back and used kl_aq_rel_alpha_n_fakt to do a linear table interpolation exactly the same as the DME does to work out AQ_REL_ALPHA_N for each log line based on AQ_REL and the RPM.

This is the before in MegaLogViewer:



And this is the after:



And to visualize it better here is the difference:



It's important to remember here that a nominal value is 1.00. This means that a difference of 0.058 is significant. It's the difference between too lean (1.059) and bang on (1.002). This of course only affects 2400rpm and under, but the effect is not small, especially given this is prime low rpm, low throttle, drivability territory.

[karter16]

I am not using one. I am under the impression that relative opening is a mixture of ICV/TPS/MAP and is directly tied to the load table. This definitely corrects the whole table as I would otherwise have a run-away condition if my cells weren’t in the right places. I’ve asked many moons ago on this forum if aq_rel is load and was told it was, what is your reasoning for the question?

For what it's worth I've just been working through this in my disassembly project and thought it would be worth noting here. Below is a summary of how it comes together:

AQ_ABS (absolute cross-sectional opening) = AQ_ABS_LLS (absolute cross-sectional opening of idle control valve) + AQ_ABS_WDK (absolute cross-sectional opening of throttle plates)

AQ_REL (relative cross-sectional opening (%)) = (AQ_ABS - K_AQ_ABS_MIN (minimum possible cross-sectional opening)) / (K_QA_ABS_MAX (maximum possible cross-sectional opening) - K_AQ_ABS_MIN)

This AQ_REL value is what's used in the standard M3 software, a commonly referenced example of this is the VANOS maps - AQ_REL is the y-axis in those tables.


The important thing to know is that AQ_REL isn't used directly in the CSL AlphaN maps. It's actually a modified version of AQ_REL that is used.

For the purposes of this explanation I will call this modified value AQ_REL_ALPHA_N it is calculated thusly:

AQ_REL_ALPHA_N = AQ_REL / AQ_REL_ALPHA_N_FAKT

So what's AQ_REL_ALPHA_N_FAKT? It's just my name for the output of the lookup curve at: 0xE056




x axis is N (rpm) and the output is a scaling factor.

Essentially what this means is that AQ_REL_ALPHA_N will be a smaller value (between 0-30% smaller dependent on RPM) than actual AQ_REL beneath 2400 RPM.

Additionally there is another value that is also calculated in the same routine, let's call it AQ_REL_ALPHA_N_PT_KORR which is additionally scaled based on P_UMG (Ambient air pressure) and TAN (Intake air temperature).



This value isn't used in the CSL AlphaN maps (or in other operational code), but it is used in two routines which seem to be involved in the sending/export of data (I haven't figured out yet if these are the DS2 routines or something else). Crucially AQ_REL_ALPHA_N is NOT referenced in any sending/export routines. Which raises the possibility that the "Relative Opening" datapoint that we are logging in TestO isn't even the same data point that is actually used as an input to the VE table (indeed it could even be the standard AQ_REL variable). Looking at the two tables above they are normalized around 20 degrees C intake temp and ambient air pressure of 962mbar, so it's not going to be too far off either way, but for example today in Auckland was 1016mbar at 20C, so PRESUMING THIS IS THE CASE I'd be looking at a 4% variance.

I will spend more time looking at this to see if I can establish with certainty which of the two variables "Relative Opening" represents.


Also worth mentioning that the MAP sensor does not have any part in the calculation of AQ_REL. The MAP sensor is used in the calculation of air mass, which in turn is used in the calculation of final Relative Fill (an adjustment to the value obtained from the VE table).


I realize this post is more focused on the "academic" side but hopefully of use to the collective understanding.

[ac427]

Filtering the log and compiling the logged data into the required table.

Thanks, Are there any suitable alternatives to MegeLogViewer HD ?

Would https://datazap.me/ do ok or is MLVHD worth the $50 ?