sjanes

I have recently replaced my boat anchor 911 battery with the 14 lb Odyssey 680, and have also installed a battyery cut off that I turn off every night to prevent any drain on the battery. A buddy of mine then mentioned to me that he thought the 3.2L DME "learned" driving habits, and that by disconnecting the power, I'm resetting the DME. So, does the DME "learn", or is it just a static mapping?

DME has a SW chip in case that matters.

Oh, in case you're wondering why I put in such a small battery, it's mainly a track car, so I remove weight where ever I can.

Thanks.

madmmac

No, it does not learn. All the fuel/timing mapping is on your SW chip and it is static. What does occur is when you have lost battery power is that the car may not run at it's potential for the first 10 minutes or so of driving as it recognizes and adjusts to the chip.

sjanes

Thanks. I don't run at my full potential for the first 10 minutes of the day either, so the car and I will be a good match.

911Dave

I've been wondering about this ever since I saw the text on page 970-1 of the Bentley manual:

"CAUTION-
Disconnecting the battery cables erases engine control module (ECM) adaptive memory. It may be necessary to drive the car for approximately 10 minutes after reconnecting the battery to reset ECM adaptive memory and restore normal performance."

What do they mean by "adaptive memory"? What is it adapting to?

84_Carrera

Adaptive memory sees patterns in your driving style (gas sipping, all-out performance, etc.) in other cars, sorry not sure on the DME setup in the 911. In the other vehicles I've worked on, it'll adjust fuel & timing maps according to your personal driving style, and can also affect idle programs, etc.

In the case of the SHO, you have to teach the PCM how to idle under load after reconnecting the power, otherwise it can stall out when you come to a stop & the AC's suddenly on, or you're working the power steering, etc.

Again, this is for other vehicles, not specific to the 3.2 Motronic necessarily.

Brett San Diego

In my understanding the ECU is not adapting to you. Rather it is adapting to your engine. It's like tuning your carbs for your engine. Only in this case, the engine is tuning itself through the DME. Every engine is different requiring slight tweaking of the fuel delivery under all ranges of conditions. The ECU has to start somewhere, so it is programmed with a general starting point, which should allow the car to run but is likely not optimal for any particular engine. As the car is driven, the ECU adjusts (or adapts) the fuel delivery appropriately, and then in a sense, it makes those adjustments permanent. (But, not really permanent because it is always updating itself by updating its adaptive memory.)

Brett

Corrales911

My understanding of adaptive memory is that the maps are "hardwired" but the computer "learns" how and when to best apply any given map.