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Registered
Join Date: Dec 2004
Location: Novato, CA
Posts: 3,064
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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
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BMW 135i. Nice. Fast. But no 911... "I will tell you there is a big difference between driving money and driving blood, sweat and tears." - PorscheGuy79 |
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12-16-2005, 09:38 PM
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Registered
Join Date: Jan 2003
Location: Langley,B.C.
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I have heard that but never experienced it........... A guy like Steve W or Loren would know the real truth of the matter......
Cheers
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Turn3 Autosport- Full Service and Race Prep www.turn3autosport.com 997 S 4.0, Cayman S 3.8, Cayenne Turbo, Macan Turbo, 69 911, Mini R53 JCW , RADICAL SR3 |
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12-16-2005, 10:17 PM
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Administrator
Join Date: Feb 2000
Location: Los Angeles
Posts: 13,334
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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.
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Jack Olsen 1972 911 My new video about my garage. • A video from German TV about my 911 |
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12-16-2005, 10:56 PM
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I'm with Bill
Join Date: Jun 2005
Location: Scottsville Va
Posts: 24,186
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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.
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Electrical problems on a pick-up will do that to a guy- 1990C4S |
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12-17-2005, 04:55 AM
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Used Up User
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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
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'87 Carrera Cab ----- “Only two things are infinite, the universe and human stupidity, and I'm not sure about the former.” A. Einstein ----- |
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12-17-2005, 05:03 AM
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Irrationally exuberant
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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
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'80 911 Nogaro blue Phoenix! '07 BMW 328i 245K miles! http://members.rennlist.org/messinwith911s/ |
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12-17-2005, 05:58 AM
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another round please
Join Date: Sep 2004
Location: Carmel In.
Posts: 4,452
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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.
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Getting old is not for wimps. |
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12-17-2005, 07:06 AM
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Registered
Join Date: May 2003
Location: Manhattan Beach, CA
Posts: 2,350
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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.
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Have Fun Loren Systems Consulting Automotive Electronics '88 911 3.2 '04 GSXR1000 '01 Ducati 996 '03 BMW BCR - Gone Last edited by Lorenfb; 12-17-2005 at 08:41 AM.. |
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12-17-2005, 08:37 AM
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Registered
Join Date: Dec 2004
Location: Novato, CA
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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
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BMW 135i. Nice. Fast. But no 911... "I will tell you there is a big difference between driving money and driving blood, sweat and tears." - PorscheGuy79 |
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12-17-2005, 11:44 AM
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Used Up User
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Quote:
Ian
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'87 Carrera Cab ----- “Only two things are infinite, the universe and human stupidity, and I'm not sure about the former.” A. Einstein ----- |
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12-17-2005, 12:05 PM
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1987 Porsche 911 Carrera Cabriolet 3.2
The Blue Pheonix
