NefMoto > Technical > Reverse Engineering > N249 activation for overboost protection
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Author Topic: N249 activation for overboost protection  (Read 9757 times)
elRey
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« on: January 06, 2014, 12:11:43 AM »
I've seen this reference by many people but have not seen anyone quote documentation or disassembled code of such function.

I have not been able to find it myself either. I say it doesn't exist, but would like someone to verify.

I prefer 1.8T application, but would accept 2.7TT if found.

Thanks,
Rey
« Last Edit: January 06, 2014, 12:56:45 AM by elRey » Logged
dream3R
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« Reply #1 on: January 06, 2014, 05:36:07 AM »
I was looking at some code in my Volvo file last week and found it to be BGPLGU.  Might be way off here, but I think this might be what you are looking for?
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How to work out values from an A2L Smiley

http://nefariousmotorsports.com/forum/index.php?topic=5525.msg52371#msg52371


Starting Rev's http://nefariousmotorsports.com/forum/index.php?topic=5397.msg51169#msg51169

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I don't have ME7.01 A2L I just use ID
phila_dot
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« Reply #2 on: January 06, 2014, 06:16:48 AM »
IIRC, it's never used for overboost protection.

With a negative pedal gradient it is activated when a boost spike is predicted such as from a closing throttle.

The function is disabled when target boost pressure is greater than atmospheric pressure.
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userpike
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« Reply #3 on: January 06, 2014, 08:40:15 AM »
not sure if this will help out but http://nefariousmotorsports.com/forum/index.php?topic=2026.msg19187#msg19187:
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elRey
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« Reply #4 on: January 06, 2014, 09:04:11 AM »
Thanks for the link. Unfortunately it doesn't shed any more light on this specific question.
« Last Edit: January 06, 2014, 09:13:51 AM by elRey » Logged
userpike
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« Reply #5 on: January 06, 2014, 09:50:16 AM »
Quote from: elRey on January 06, 2014, 09:04:11 AM
Thanks for the link. Unfortunately it doesn't shed any more light on this specific question.

I just did a search in the FR for "Schubumluftventil" and found 2 modules, LDUVST and DLDUV they say nothing I can see about anything having to do with overboost. I also tried just "Umluftventil" but it brought me to every spot the first search did through all the pages. I was thinking maybe the definition would be in some other module and the search would find it but there wasn't anything else. This leads me to believe the N249/DV doesn't have a function for overboost.

Thinking about this for a sec I don't want the DV to dump while the turbo is overboosting because taking the load off the compressor wheel I believe would make for an over spin condition without the N75/WG being dumped also. I could be wrong.
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elRey
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« Reply #6 on: January 06, 2014, 10:23:15 AM »
Quote from: userpike on January 06, 2014, 09:50:16 AM
I just did a search in the FR for "Schubumluftventil" and found 2 modules, LDUVST and DLDUV they say nothing I can see about anything having to do with overboost. I also tried just "Umluftventil" but it brought me to every spot the first search did through all the pages. I was thinking maybe the definition would be in some other module and the search would find it but there wasn't anything else. This leads me to believe the N249/DV doesn't have a function for overboost.

I also tried searching doc for B_ldsua, B_ldsuas, B_ldsuad AND I identified variables in disassembly and search for all writes. I found the same as you. Hence, why I brought this up.

Quote from: userpike on January 06, 2014, 09:50:16 AM
Thinking about this for a sec I don't want the DV to dump while the turbo is overboosting because taking the load off the compressor wheel I believe would make for an over spin condition without the N75/WG being dumped also. I could be wrong.

Very good point.
« Last Edit: January 06, 2014, 10:35:04 AM by elRey » Logged
elRey
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« Reply #7 on: January 06, 2014, 01:53:05 PM »
Quote from: phila_dot on January 06, 2014, 06:16:48 AM
IIRC, it's never used for overboost protection.

With a negative pedal gradient it is activated when a boost spike is predicted such as from a closing throttle.

The function is disabled when target boost pressure is greater than atmospheric pressure.

It would be nice to know how you came to this understanding.
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nyet
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« Reply #8 on: January 06, 2014, 01:57:11 PM »
Quote from: userpike on January 06, 2014, 09:50:16 AM
Thinking about this for a sec I don't want the DV to dump while the turbo is overboosting because taking the load off the compressor wheel I believe would make for an over spin condition without the N75/WG being dumped also. I could be wrong.

Well put. Thanks for pointing this out.

BTW this is also why boost leaks are so bad, and another reason to not remove underboost -> limp protection.
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dream3R
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« Reply #9 on: January 06, 2014, 03:14:17 PM »
Quote from: elRey on January 06, 2014, 01:53:05 PM
It would be nice to know how you came to this understanding.

Same, +1.
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How to work out values from an A2L Smiley

http://nefariousmotorsports.com/forum/index.php?topic=5525.msg52371#msg52371


Starting Rev's http://nefariousmotorsports.com/forum/index.php?topic=5397.msg51169#msg51169

noobs read this before asking http://nefariousmotorsports.com/forum/index.php?topic=9014.0title=


ORGORIGINAL 05 5120 creator for Volvo
ORIGINAL Datalogger (Freeware) Author
ORGINAL finder of the 'extra' torque' limits
I don't have ME7.01 A2L I just use ID
elRey
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« Reply #10 on: January 06, 2014, 03:23:18 PM »
To seed the continued discussion and convey I'm looking for examples of documentation and/or code:

The function LDUVST describes N249 control. No where in it does it reference B_ldob,E_ldo or any other upper limit (boost or MAF).

And no where else in doc is are variables B_ldsuad, B_ldsuas, B_ldsua set. I confirmed the same in 1.8T disassembled code.
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