Adaptive parameters

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

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.

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.

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

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