If you take the cover off the MBE ECU, you’ll find 2 large chips.
The one that Joolz labelled with the sticker when he was mapping it, is the EPROM, it is where the main tuning map is stored.
Below that in the photo is the Dallas NVSRAM chip. This chip is responsible for storing the adapatives/learned values.
These 2 chips then work together.
When the car first powers up, the base map is loaded that contains the 3D tables for fuel, ignition timing, idle target speed etc.
Then the adapatives are read that then apply minor adds/subtractions corrections to the base map.
While driving, the ECU constantly monitors the Lambda sensors, coolant temp etc and writes small corrections to the adaptives chip.
Next time the car is started up, these improved values are again reloaded and so on.
What this means is, that the ECU is continually adjusting its map based on your driving style and conditions, which results in a smoother running car.
All very well and good. However..
..the problem though is that the Adaptives chip has an inbuilt lithium battery, that has a service life of approx. 10 years. Once the battery is no longer working, then the values written to the Adaptives chip are lost each time the car is started, meaning you are always reverting back to using the Base map.
What does this mean in the real world?
If you were using your car through Spring, Summer, Autumn and maybe a little in Winter- with a fully functioning adaptives chip, each time you used your car, the values would be tweaked a little, and you should notice no rough running between drives.
However with an adpatives chip with no memory, you’d always be going back to the base map, and probably experience rough running on initial startup during hot/cold seasons because the chip hasn’t had those incremental changes made as you drive it through the seasons.
The date code on my chip was 9843. week 43 in 1998. So this chip was 28 years old! The battery in this was for sure dead.
The replacement chip has a date code of 2447. week 47 in 2024. (note, the 10yr life span starts once the chip first receives power)
Other markings on the chip and what they mean:
My old chip
DS1230AB – is the name of the chip
200 – measured in ns is the speed of the chip (higher number is slower, lower number is faster)
IND – short for industrial, means the chip is certified to operate in sub zero or very hot temperatures
My new chip
DS1230AB – same as the one replacing it
120 – this chip can operate faster than the one it is replacing.
IND – same as above
plus sign – means it is lead free
The chip itself is easy to remove and replace, it simply pulls out. Just make sure you’ve disconnected the 12v battery and are using an anti-static wrist strap.
Thanks to Nick & Joolz for the heads up on this chip.