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Title: N249 activation for overboost protection Post by: elRey 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 Title: Re: N249 activation for overboost protection Post by: dream3R 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?
Title: Re: N249 activation for overboost protection Post by: 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. Title: Re: N249 activation for overboost protection Post by: userpike 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:
Title: Re: N249 activation for overboost protection Post by: 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.
Title: Re: N249 activation for overboost protection Post by: userpike on January 06, 2014, 09:50:16 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. Title: Re: N249 activation for overboost protection Post by: elRey on January 06, 2014, 10:23:15 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. 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. Title: Re: N249 activation for overboost protection Post by: elRey on January 06, 2014, 01:53:05 PM 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. Title: Re: N249 activation for overboost protection Post by: nyet on January 06, 2014, 01:57:11 PM 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. Title: Re: N249 activation for overboost protection Post by: dream3R on January 06, 2014, 03:14:17 PM It would be nice to know how you came to this understanding. Same, +1. Title: Re: N249 activation for overboost protection Post by: elRey 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. |