Degraded DME perf after batt disconnect?
 

Hi folks,

The factory manual, or the Bentley, or both, or something, says that you'll notice less than optimal driving characteristics for about 10 minutes after disconnecting the batt due to the learned driving behavior being in VRAM (volatile) only, and hence purged upon batt disconnection.

Anyone noticed this? What happened? I plan to do other work concurrently with the batt disc, and I wondered what other people had seen. Thanks for the fo,

ianc

I have heard that but never experienced it........... A guy like Steve W or Loren would know the real truth of the matter......

Cheers

I've reset my DME several times. I'm told there's a difference as the computer 'learns' its driver, but I've never felt it.

The only way I know to make the DME "stupid" by use of the batt. is to remove both terminals from the batt. and hook them togeather for a few seconds. This causes a forced discharge of all the capistors in the car. On the obd2 cars it can be done with a scan tool it is called clearing the self learning. Idle and the shift quality of an auto trans should be the only things noticed.

Not answering the question, but here is a great DME resource. It's specifically for the 944 but I believe it's the same or very similar.

The 944 Motronic DME by FR Wilk

More DME fun:

Motronics Editing - Recommended Hardware and Software

Motronic Editor

Ian

I have never seen anything in or about the pre-964 DME's to make me think they have any adaptive capability. I think the 964's had it though.
(I could be wrong of course.)
-Chris

I have a battery disconnect on my 86, and always turn it off for the week. I have a drain on it that I cant find yet. Each time I start it up, it burps, sputters, etc. for about 5 minutes, but then it works fine. I dont nitice any difference in driving.

There's no adaptive function in the 3.2 DME unit and no stored values.
The 964 DME has limited adaptive capability, i.e. it will adapt/optimize the
O2 range for proper control for problematic AFRs (intake air leak, slightly
high fuel pressure, & altitude). This function is similiar to what the 928S4
LH system had and BMW in the late '80s early '90s.

The 964 DME also has the capability to use stored input values, e.g. temp
sensor, in the event that the sensor becomes out of range. Because of this
and the limited adaptive function, it has a stored volatile memory, i.e lost
values with battery removal.

Hmmm... Page 201-10 of the Bentley Carrera manual warns of degraded perf after disconnecting the ECM. Guess it's crap then? Not the first time the Bentley's been wrong...

The beeyotches left out the whole G50!

ianc

Your's too? I thought that was just my copy . . .

Ian