Background.
I got to where I am through this thread https://www.rx8club.com/series-i-tro...-610-a-256168/

Both ECUs have been "refurbished". By that I mean they were tested, some parts were considered lacking (mainly transistor packs) and they were replaced. They are now reflashed and closed back up. All the testing was done with the factory tune, with drive cycles. I am starting to hate drive cycles.

Really Odd Observation:
When I put the original ECU back in the first time, after the refurbish, before a reflash, and got the car running, I noticed the range and the cumulative MPG started to climb on my ultra gauge. I did not think much of it. When I put in the used and reflashed ECU, it was still climbing. I have a pretty set commute, with back roads and constant speeds. The highest numbers I see are a 45 mph level section. With these ECUs, the highs are now in the 28 to 30 range (2 to 3 above a month ago). Today I had a 28, going into a head wind, with the AC on. And, I drive this route with cruise control on to foot based variations are unlikely.

I started thinking about what these replaced transistors could be doing and came up with firing coils, firing fuel injectors and important things like that. And the question becomes, does it makes sense that a new set of control devices would do a cleaner and more precise job of switching power than an 11 year old set that has driven the car 138,000 miles? And, if they did, is it worth a 10% or greater increase in MPG?

And yeah, I think I am getting the mileage. The average from last 8 moths was what was starting to rise. So was the miles projected from each tank (sum of trip odo plus distance to empty rises throughout the tank).

Am I missing something?

I have since reset the *** MPG to precisely check mileage across a few tanks. But it is tracking what I expect so far. I also went back to my custom tune as I have a track day coming up and want to get some cycles in place. (I may go back to factory after the event for more testing) Indications are this one is as good or better than the factory tune, and was the one responsible for the data prior to a month ago.

Comments? Do we even care?

 

you should make it clear that it's a 2004 model, which there were numerous PCM revisions that year ...

 

Yes, it is an 04. I did not know about PCM revisions... The depending on how you read serial numbers on them, the two I have are not that far apart. Any idea what the revisions were for?