NefMoto > Technical > Tuning > [B58][MG1] Load Target Oscillating under Partial Throttle at low RPM
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Author Topic: [B58][MG1] Load Target Oscillating under Partial Throttle at low RPM  (Read 1590 times)
psyko
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Hi All, somewhat of a novice here so please bear with me...

I have hand-tuned a map from stock reference using the Bootmod3 map editor. I am puzzled by some behavior I am seeing under partial throttle when I am in a low RPM range and high gear (like 4th gear from 2,800 RPM and ~60% throttle). You can see the log here -- https://www.bootmod3.net/log?id=6572106bfcd6f0422ff210bc

Can anyone offer some insight in to why my load target might be oscillating like this?? I have no clue. The car feels amazing under WOT in all gears, but is behaving poorly in partial throttle in this specific case I mentioned, you can really feel the car "surging" and it's not too pleasant. Here is a WOT log to show I'm not totally full of sh*t lmao -- https://www.bootmod3.net/log?id=65720d286862a64331578dfa ; I've found this to be way more performant than any OTS map I have tried.

My engine setup is mostly stock (2020 BMW M340i), I have new spark plugs with a smaller gap, splash of E85 in my Cali 91 tank (2.5-3 gal of E85), and a VRSF catless downpipe.

You can even see here in 5th gear the transition from oscillations to smooth once the pedal is closer to WOT and the RPMS are higher -- https://www.bootmod3.net/log?id=65720fa752baf04fb71abb36

Any help is extremely appreciated! I am pretty new to this and still learning. I would love to solve this problem
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James1
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« Reply #1 on: December 08, 2023, 08:47:02 AM »
I have seen this before on this car on certain software versions.  I did not investigate it.  The way to do is to use Vehical and log all the inputs to rf_soll to see what is tripping it. 
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psyko
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« Reply #2 on: December 08, 2023, 09:04:06 AM »
Quote from: James1 on December 08, 2023, 08:47:02 AM
I have seen this before on this car on certain software versions.  I did not investigate it.  The way to do is to use Vehical and log all the inputs to rf_soll to see what is tripping it. 

I will try this next, thank you -- although I am not sure what rf_soll is yet  Embarrassed
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psyko
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« Reply #3 on: December 10, 2023, 06:17:30 PM »
I guess rf_soll is the load target. In my logs you can see even the torque target modulating (but not the "pre drive dynamics" target).

I think this implies that the transmission is limiting the torque and that's why it's oscillating; I'm going to try a transmission tune and see if that fixes the problem
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prj
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« Reply #4 on: December 11, 2023, 12:37:41 AM »
Quote from: psyko on December 10, 2023, 06:17:30 PM
I guess rf_soll is the load target. In my logs you can see even the torque target modulating (but not the "pre drive dynamics" target).

I think this implies that the transmission is limiting the torque and that's why it's oscillating; I'm going to try a transmission tune and see if that fixes the problem
You're wrong and it won't.
Trans only has a max limiter, which is not in play at part throttle.

If you're serious about this, you need a proper logger, FR and a lot of time.
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psyko
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« Reply #5 on: December 11, 2023, 09:44:31 AM »
Welp, thanks for saving me money lol.

Are you sure that even at partial throttle if the torque request is exceeding the trans limit the trans won't limit it??

I am pretty sure that the torque request is a simple mapping from the accelerator pedal multiplied by the max torque tables, I can try lowering those, but then I will lose power. The only way this would get affected is by something outside the DME (I think the TCU here but you say I am wrong...)

I am serious about it, I agree it may take some time, but I am dedicated to figuring it out
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prj
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« Reply #6 on: December 11, 2023, 11:02:46 AM »
Quote from: psyko on December 11, 2023, 09:44:31 AM
Welp, thanks for saving me money lol.

Are you sure that even at partial throttle if the torque request is exceeding the trans limit the trans won't limit it??

The ZF8HP only has a max torque limit per gear, nothing else.
If on WOT it makes more torque than on part throttle, then that limit is not in the way, I don't know what else to tell you.

Also these variables don't mean what you think they mean.

If you want to actually understand what you're looking at you're gonna need to grab an FR and a full ram logger.
Right now you're just jumping to conclusions based on wrong data.

You will also probably need a full editor, and not just what is cherry picked for you.
« Last Edit: December 11, 2023, 11:09:05 AM by prj » Logged
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James1
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« Reply #7 on: December 12, 2023, 03:18:39 AM »
From memory, BM3 logger allows you log a byte for torque and for load limiting.  The value tells you what is triggering the limiter.  If you can log that it is going to speed things up greatly.
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psyko
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« Reply #8 on: December 12, 2023, 06:23:16 PM »
Quote from: James1 on December 12, 2023, 03:18:39 AM
From memory, BM3 logger allows you log a byte for torque and for load limiting.  The value tells you what is triggering the limiter.  If you can log that it is going to speed things up greatly.

I'll take a look here

Quote from: prj on December 11, 2023, 11:02:46 AM
The ZF8HP only has a max torque limit per gear, nothing else.
If on WOT it makes more torque than on part throttle, then that limit is not in the way, I don't know what else to tell you.

Also these variables don't mean what you think they mean.

If you want to actually understand what you're looking at you're gonna need to grab an FR and a full ram logger.
Right now you're just jumping to conclusions based on wrong data.

You will also probably need a full editor, and not just what is cherry picked for you.

Got it. Yeah, I do feel that the editor is limited here -- can you suggest an alternative?

I will try to find the FR for MG1... and will get VehiCal soon
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prj
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« Reply #9 on: December 13, 2023, 01:01:53 AM »
Usually WinOLS is used, but you will need the damos for your ECU as well.
I don't know if your editor has enough maps to fix the problem, you will find that out once you have a FR and log some variables.
If you arrive at something you can't change with your editor, then you will need to upgrade.

Usually the weird problems are outside of the scope of dumbed down editors, because they happen deeper in the ECU, and the end-user solution rely on basemaps where more complex issues are fixed and the end-user never has to encounter them.
The only way to solve them is the slow systematic approach of going through diagrams and logging everything until you find where one or the other behaviour is coming from.

That said, if you have modified KFMDIOP (I believe it was called that on BMW? The load to torque maps) and scaled them weird to get around transmission limitations, then try to scale them back to stock and see if you get the same behaviour.
If you do, then a trans tune with lifted torque limiters will actually help you (so that you don't have to screw up the maps to get around it).

If it doesn't do it stock, then chances are it's something you did during the tune.
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