Originally Posted by vec
i'm thinking about miata in the NB series.
If your plans include forced induction (and since you're here, I assume they do) just know that each generation has its own particular quirks in this regard. The signifigance of these depends on your intentions as regards engine management, and your level of tolerance and skill with both electronic and software tinkering.
The 1.6 NA ('90-'93) and early 1.8 ('94-'95) are dead-simple to work on. There's just no other way to put it. You can build a vacuum-tube based ECU, install a turbo pulled from a Cat diesel, and run the engine on whale oil with one of these cars.
Starting in '96, you have the OBD-II computer system to deal with. If your town does smog-testing via plug-in diagnostics, this will limit your options slightly, ruling out full-replacement ECUs and complicating the matter of piggyback ECUs slightly, as you'll have to be more careful not to set off a CEL.
The NBs are a little
tougher. Their returnless fuel system complicates the use of old-school adjustable fuel pressure regulators, but frankly I don't recommend them for new installs anyway. Electronic fuel management is so much easier and more precise. Some of the engine sensors are also a bit different, and while it's still possible to run nearly any engine management system on them, they're just not as widely understood. Some NB folks actually install the older NA sensors on their engines, though this is not absolutely necessary.
In case you didn't know, there are no "chipped" ECUs. If you want electronic engine management, you either install a piggyback / parallel computer, or pull the ECU out entirely and run a MegaSquirt. A few renegade hackers have successfully cracked the OEM ECUs, however no commercial products seem to have evolved of this, at least not any we've seen much of in the US.