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

[Bry5on]

Ran through the karter16 updated VE tuning method on my car today. Car is running Bry5on's latest mullet (v28) and I disabled MAP and adaptations during the data logging sessions.

Here's the final change compared to the baseline after three iterations:



There was a little bit of weirdness left down low (<1500 rpm and <~1.5 relative opening) before the tuning. It was mostly noticeable when pulling away from a stop and when feathering the throttle right before fully disengaging the clutch on upshifts. Was extra noticeable with the stock comfort throttle mapping.

But all that is practically undetectable post-tuning! I'm super happy with the results. Drivability is very, very, very close to stock now.

Super wild how different the results are between the two cars after running the same optimization! I wonder if you have a looser ICV than I do? That’s the only thing I can think of that would need that much extra fuel down low.

[heinzboehmer]

Super wild how different the results are between the two cars after running the same optimization! I wonder if you have a looser ICV than I do? That’s the only thing I can think of that would need that much extra fuel down low.

Yeah I don't get it either. Injectors are the only other thing I can think of. Although our cars are dead on in the upper RPM/load ranges, not sure what to make of it.

I have a set of TT injectors in the garage, but haven't swapped them cause I haven't been ready to go down that rabbit hole.

[karter16]

Okay so when it comes to the cold-start map I think the presumption has been to log up until the point that TMOT is at 80 degrees C at which point the engine is warm and on the standard map.

As I was chasing the last few parameters I came across this again and looked at it in a slightly new light. the Alpha N Kath table is blended in based on AVAN1_SOLL_FAKTOR. But why use AVAN1_SOLL_FAKTOR and not KATH_FAKTOR directly. Last time I looked at this I wasn't in the detail enough to question it, but it seems to be an interesting choice.



AVAN1_SOLL_FAKTOR is calculated on the slave here:



The key thing to note is if EVAN1_ST bit 4 is set then AVAN1_SOLL_FAKTOR ramps to 1 over a few seconds) if bit 4 is cleared then AVAN1_SOLL_FAKTOR ramps to 0. So it's either on or off with a bit of smoothing over the few seconds of the transition.

How is EVAN1_ST set?

bit 4 is set here:



What this is doing is using the curve KL_VAN_KATH_TMOT to determine how long EVAN1_ST should be cleared for before it is set.



First time the function runs and engine is in running state (LL/TL/VL) it checks current TMOT and looks up how many seconds the warm up period should last for. (e.g. if TMOT is 18 degrees C then the warm up will last for 120 seconds).

EVAN_1_ST bit 4 stays cleared for 120 seconds and is then set.

So the warm up period that the AlphaN Kath table is used is a set number of seconds based on TMOT at the time the engine starts, not a temperature target that is achieved by the end of warm up.

So back to my original question, why are we using AVAN1_SOLL_FAKTOR rather than KATH_FAKTOR. Thinking about it a bit more it actually makes a fair bit of sense. Use of the AlphaN Kath table is tied to the use of the VANOS Kath tables because the different camshaft tables affect the volumetric efficiency and therefore the AlphaN table needs to be tuned to the VANOS Kath profiles. Likewise they both use AVAN1_SOLL_FAKTOR as they need to switch together as well.


Anyway, why am I writing this in here? Because we should stop presuming that the AlphaN Kath table is used until TMOT >= 80 degrees and come up with a different strategy (We could probably log AVAN1_SOLL_FAKTOR over DS2, or we could log TMOT on engine start and work out how many seconds into the log file to take data from from there).

Not sure in practice how much this will really affect anything but might as well make sure we have the most correct knowledge :-)

[Bry5on]

Can we log short term adaptations and watch for the first transition from 1? If I remember correctly, adaptations are forced to 1 during this period - hence the difficulty in tuning cold start fueling.

[karter16]

Can we log short term adaptations and watch for the first transition from 1? If I remember correctly, adaptations are forced to 1 during this period - hence the difficulty in tuning cold start fueling.

Ah good thinking - I'll dig into that but that sounds like a very good option.


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