Adaptive parameters
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Category: Technical & Model Specific Forums
Forum Name: BMW ///M Power
Forum Discription: Ask your BMW M Power Technical Questions here (M1, M2 hybrids, M3, M5 & M6)
URL: http://www.bavarian-board.co.uk/forum_posts.asp?TID=17115
Printed Date: 15-May-2024 at 01:01
Topic: Adaptive parameters
Posted By: __Andy__
Subject: Adaptive parameters
Date Posted: 28-April-2005 at 05:26
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Who understands the magic of the ECU box? When I disconnect the battery and let the ECU reset its parameters, the car runs just fine but gets steadily stronger (optimax) for a few hundred miles then gradually assumes the trademark smoothness I'm used to. I just had it chipped (details after dyno visit) and same thing. Fair enough, ECU out so reset. Immediately afterwards it didn't feel opbviously quicker, but gradually it's improving and now perhaps 200 miles in, it's starting to get smooth and I'm sure faster than before (I should hope so). So question is, which parameters are being adapted by the ECU and how does it figure out what their optimum is? The TIS mentions procedure but doesn't give any technical information. Cheers Andy |
Replies:
Posted By: micky_h
Date Posted: 28-April-2005 at 06:20
It's witchcraft  wish I knew myself.But I would assume the car measures air flow,fuelling/fuel quality maybe,alters the ignition timing until it finds it's optimum settings.Am sure someone on here will know better though 
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Posted By: siwilson
Date Posted: 30-April-2005 at 05:48
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Hmm, So does the ECU learn forever or learn for a while and then stick with certain settings? I am thinking about changes you make such as if the engine was running on el cheapo petrol during the learning process, would it adapt later? What if you the change the exhaust or induction system. Does the ECU adjust for this or does it assume the same settings it used when it first learned your setup? Just curious. |
Posted By: 215DMX
Date Posted: 30-April-2005 at 14:20
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Basically I would say the ecu is stupid. It can only do
what it knows to be 'OK'. When you reset the ecu it is starting fresh with base settings. As the engine runs it creates data which it stores, this data would include the readings from all the various sensors, it then 'knows' that a certain fuel you have in the car, altitude, air density etc will produce a certain result. By having these look-up tables it can then just refer to them when those same conditions arise again and trim the fuel and ignition to give the optimum setting. On TVR's, well at least ones from 3years ago anyway, if you didn't give them some thrash on a regular basis the ecu changed to a higher torque/ lower rpm bias because the ecu 'assumed' your didn't need/ want high rpm power. IMHO. |
Posted By: siwilson
Date Posted: 30-April-2005 at 15:03
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So are you saying it builds a table then then sticks with that or it builds a table and continues to modify it ? I am just wondering if it is worth a reset so it teaches itself about life and optimax now I have the Eisenmanns fitted. |
Posted By: 215DMX
Date Posted: 01-May-2005 at 04:39
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It's continually 'learning' and adapting. Wether or not
resetting it would make it learn 'better' ?????????? Give it a try. |
Posted By: Nigel
Date Posted: 01-May-2005 at 04:43
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Interesting question, I cant promise you'll get an answer, but try the new tech e-mail helpline Robert Stern have kindly given us. http://bmwcarclubgb.co.uk/regions/centrl/robertsterns.htm - http://bmwcarclubgb.co.uk/regions/centrl/robertsterns.htm ------------- Best Wishes Nigel |
Posted By: micky_h
Date Posted: 01-May-2005 at 09:21
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You can have a look at this too,might not tell you all you need to know but is interesting anyway.
http://www.bmwworld.com/technology/dme.htm - http://www.bmwworld.com/technology/dme.htm |
Posted By: autofix
Date Posted: 01-May-2005 at 17:25
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Hi Guys, The situation will vary for different management systems but the basic idea is the same. Your engine management ECU is programmed with thousands of ignition and fuel "maps". These maps are basically just instructions which tell the ECU what to do with the ignition and fuel. The ECU is programed to adopt a basic map and then to adapt from that to similar maps based on what it learns from the systems sensors. The oxygen sensor is the most important one in this process. This self-adaption is needed to allow for wear in both the engine and in the management system. The ECU is programmed to allow only a certain amount of adaption. When this limit is reached a fault code is stored. When you reset adaptions, all you do is start it back at its base setting and it starts to learn over again. Now if you raise compression and fit a wild cam, the ECU will not be able to adapt for this as there would not be suitable maps present as well as it being outside the pre-programmed limits. This is why re-mapping is done. If the adaptions need to be changed, for example after a fault has been fixed, the ECU will do this itself. Clearing adaptions just speeds things up a bit. As a bit of an aside. Some of these adaptions can be seen by reading live data in the form of fuel trims. These are very useful as a diagnostic aid. Alan
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