Do BMW do adaptive ECUs ?
Discussion
Hi Folks.
Been pottering around town a fair bit of late in full granny mode until I got an all-too-rare moment to nail it (in my 08 330i). To be honest it was pretty underwhelming and it got me thinking of a thread I read on the Audi S4 linky. Seems like if you drive one of these like a pussy (ie like me lately
) you're not getting full throttle even when you do floor it.
So do BMWs have anything similar or am I just losing it ?
Cheers, DD.
Been pottering around town a fair bit of late in full granny mode until I got an all-too-rare moment to nail it (in my 08 330i). To be honest it was pretty underwhelming and it got me thinking of a thread I read on the Audi S4 linky. Seems like if you drive one of these like a pussy (ie like me lately
) you're not getting full throttle even when you do floor it. So do BMWs have anything similar or am I just losing it ?
Cheers, DD.
miniman said:
Several theories, most popular are:
Turn on the ignition for 10 seconds, it is not necessary to crank or start the engine.
Turn the ignition off for 10 seconds.
Start the engine.
(although this comes up more with E46 3-series)
or
Key in
Switch on
Hold down throttle for 60 seconds
Thanks James - I will give this a try and report back !Turn on the ignition for 10 seconds, it is not necessary to crank or start the engine.
Turn the ignition off for 10 seconds.
Start the engine.
(although this comes up more with E46 3-series)
or
Key in
Switch on
Hold down throttle for 60 seconds
Hi Guys.
Sorry for droning on about this adaptive ECU business but I just wondered if anybody knows how it works ? More specifically :
1. How long does it take to adapt - ie how often should I reset it ?
2. What does it actually do ?
3. Why ??
4. Would it still happen on a 'mapped' car ?
Cheers, DD
PS - sorry again as this is crashingly dull stuff and I clearly have too much time on my hands !!
Sorry for droning on about this adaptive ECU business but I just wondered if anybody knows how it works ? More specifically :
1. How long does it take to adapt - ie how often should I reset it ?
2. What does it actually do ?
3. Why ??
4. Would it still happen on a 'mapped' car ?
Cheers, DD
PS - sorry again as this is crashingly dull stuff and I clearly have too much time on my hands !!
dibbly_dobbler said:
Hi Guys.
Sorry for droning on about this adaptive ECU business but I just wondered if anybody knows how it works ? More specifically :
1. How long does it take to adapt - ie how often should I reset it ?
2. What does it actually do ?
3. Why ??
4. Would it still happen on a 'mapped' car ?
Cheers, DD
PS - sorry again as this is crashingly dull stuff and I clearly have too much time on my hands !!
There are 2 forms of adaptation, one is in the Autobox, where driving style and probability is recorded, a cruiser would avoid shifting on a dab of throttle, whilst more spirited driving would mean the ecu expects a prolonged period of throttle, so would down shift.Sorry for droning on about this adaptive ECU business but I just wondered if anybody knows how it works ? More specifically :
1. How long does it take to adapt - ie how often should I reset it ?
2. What does it actually do ?
3. Why ??
4. Would it still happen on a 'mapped' car ?
Cheers, DD
PS - sorry again as this is crashingly dull stuff and I clearly have too much time on my hands !!
The autobox doesn't know what you want to do next, so it "learns" what you are likely to do next.
Adaptation in the ECU comes in 2 parts. The first is the ODB2/EOBD adaptation for emission control.
This is fine tweaking of of the maps to counteract wear and tear, dirty injectors and air leaks.
For example, the ECU will have a programmed target lambda on a petrol car. If the fuel filter becomes clogged, the car will start to run a little lean.
Short term adaptation is carried out almost immediately from feedback from the lambda sensor.
It's worth noting that narrowband lambdas can only measure excess oxygen, so rich conditions can't be measured apart from the fact there is no oxygen left, so it isn't able to know how rich the mix is. Likewise, the narrow range won't show too much details on how lean due to the response of the sensor.
The reactivity of the sensor isn't too quick either, so after about 3000-4000 rpm it can't react quick enough to provide anything useful so the car operates in the dark based on the programmed info.
One way of imagining it is driving on a motorway with your eyes shut over the hard shoulder rumble strips, where you'd weave in and out over the strip where you can feel it, but once you veer off to one side, you can't tell how far away it is.
Zig-zagging over it will keep you roughly heading in the right direction.
From the info collected from the short term adaptation (below 3500-ish rpm) the car builds a picture of the general state of play.
If it has been adding extra fuel through the short term trim, it then gets added to a long term bank.
The adaptation comes in 2 flavours, multiplicative and additive, y=mx+c if you remember maths, where it can add a set value or a percent onto the trim.
This long term trim can then be used in the "dark areas" above 3500rpm where the lambda is of no use, which keeps the fuel mix at the right values even with clogged filters when it can't be measured.
Resetting an ECU deletes all the long term trim info, which makes the car run rich or lean for a while until it figures out how wrong it is. This change in feel is what is usually taken for some sort of amazing repair. A small difference can be felt, and although this is invariably for the worse, people report it as being a benefit.
Infact, it's the equivalent of swapping worn parts onto a pre-OBD2 car just to mess up the mix.
The next level of adaptation isn't emission based, but is for calibrating the throttle pedal.
Most cars these days have electronic throttles, where the pedal travel doesn't directly connect to the throttle plate, but it used more like a thrust control, and the movement is taken as a request for torque / % acceleration wanted.
In most cases, the car over throttles, so 40% on the pedal gives 60% plus throttle opening.
the height is % movement of the of the butterfly, the left axis is %pedal travel, and rpm on the right.
You can see that at lower revs, anything over 60% comes out as full throttle, and as the engine speed increases, the sensitivity is reduced.
Because the ECU is now incharge of the throttle, there has to be more safety features added in to make sure a bad sensor won't give you a runaway car.
What is done is 2 potentiometers are used on the pedal and on the throttle. From the BMW for example, the 2 potentiometers both increase with travel, with one running from 0-5v, and the other from 0-2.5v
Full throttle will be 5v / 2.5v, and 50% will be 2.5v/1.25v. As one potentiometer should always be roughly double the other, it gets 2 usable signals, and also can check one against the other to make the potentiometers are OK.
On the throttle plate, the potentiometers are 0-5v and 5v-0, so as one increases, the other will decrease by a similar amount. Yet again, it has 2 signals and self checking for wear or damage.
The throttle is moved by an electric motor, so an adaptation needs to be carried out before use so the ECU check calibrate the pedal and throttle potentiometers so it knows what is closed and full throttle.
ie, it'll swing the throttle plate about a few times and measure what the potentiometers say for closed and full throttle so it knows what it is aiming for, it'll also be able to get an idea of the smoothness of the throttle motor, and any slight variations in the potentiometers if they run out of linearity somewhere along the travel.
Resetting the throttle adaptation forces the ecu to carry out the throttle measurements again.
The post above looks in depth - it's good to get some science behind this topic. If i'm reading it correctly (which i think i am) would it actually be detrimental to the drive of a manual car to reset the ECU, as it removes all the data it has spent building up to get a picture of operation?
Well, the throttle adaptation can be good, but it will self adapt over time anyway, just slower, but for the other adaptation, yea, it's not a great idea to wipe it.
For the autobox ecu, BMW say never reset it unless you have changed the gearbox. As for the engine, maybe the uncorrected state produces a little more power, it might overfuel just a fraction, but it'll tune itself out of that after a few drives.
For the autobox ecu, BMW say never reset it unless you have changed the gearbox. As for the engine, maybe the uncorrected state produces a little more power, it might overfuel just a fraction, but it'll tune itself out of that after a few drives.
TheEnd - thanks for all the info oh wise one! 
That is some very impressive technical knowledge.
So was I just kidding myself when I did the reset procedure and it felt faster/more responsive afterwards ?
I previously thought (wrongly as I now know) that the adaption was reducing power/torque or some such on the assumption that the car was being driven by a granny ! Indeed now that I think about it, when I first changed from my 130 to the 330, the 330 initially felt faster which goes against power/weight ratios so I had presumed it was explained by the adaptive ecu malarky.
As a broad rule of thumb would I be best off just leaving it alone ?
Thanks again, DD.
That is some very impressive technical knowledge.So was I just kidding myself when I did the reset procedure and it felt faster/more responsive afterwards ?
I previously thought (wrongly as I now know) that the adaption was reducing power/torque or some such on the assumption that the car was being driven by a granny ! Indeed now that I think about it, when I first changed from my 130 to the 330, the 330 initially felt faster which goes against power/weight ratios so I had presumed it was explained by the adaptive ecu malarky.
As a broad rule of thumb would I be best off just leaving it alone ?
Thanks again, DD.
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