84-86, 87 and 87-89 DME Differences

[brcorp]

What, if any, differences are there between the 24 pin 84-86, 24 pin 87 and 28 pin 87-89 DME? During the 87 model year there was a change to the DME from 24 to 28 pins, what is the difference? And finally are 24 pin 84-86 and 24 pin 87 units interchangeable?

[RickM]

I don't think the change over is as clear cut. There seems to be exceptions to the 24-28 pin rule either way on the time scale. The later 24 pin and 28pin chips have more storage capacity. The mapping was a bit more aggressive regarding timing and fuel for the newer US cars as gas quality was percieved to be better in the US.

[RickM]

To add...here's a site with a nice breakdown of the chip charecteristics:

http://members.rennlist.com/messinwith911s/DMEHacking.htm

[RickM]

Originally posted by brcorp
And finally are 24 pin 84-86 and 24 pin 87 units interchangeable?

According to the instruction link provided in the site I listed above you should be able to: http://members.rennlist.com/messinwith911s/DMEJumperChange.htm

[brcorp]

RICK

THANKS!