While doing some work the other day I replaced my 1990 Legacy ECU with a 1993 Legacy ECU I had on the shelf. The work at hand isn't really the post here, I had an odd thought about those computers.

 

The 90 was visibly different from the 93, with a 2 holes in the case and a whole other part number series etc etc that got me thinking about the contents of the boxes

 

Would anyone know if there were any refinements to the computers, slightly different timing, fuel curve, etc etc that might have been incorporated as the series ran? It seems reasonable to me that there would have been subtle changes in the contents of the ECU programming over the first year of introduction.

 

It's academic, I know, but I'd be interested to hear if there were. I may have had 'free' hp or torque sitting on my shelf and not known it.

Ya, they did change. When they went to red top injectors they changed the computer as well. I am sure that it's just slight changes in injector flow, that sort of thing, but yes, there was a change. Usually when you swap out the non red top injectors for red top injectors, I was told to replace the ecu as well since it changed. There might be more on that in my injector thread...