OE ECUs: Difference Between Ours and Theirs?

[Soledad]

Okay, kiddie winkies, I have a few questions regarding OE ECUs, and since I can't seem to get a definitive answer from the delightful old curmudgeons on the 'other' Miata forum, I figured I'd ask here.

I'd like to know the difference between the '90-'93 NA OE ECUs; specifically the B63H that Japanese Roadsters use and the B61P that our Roadsters use. I do know that the B63H does not have a barometric sensor in it like ours does. What purpose does the barometric sensor serve, and why does the B63H ECU not utilize one? I also know that the B63H has a higher rev limit - something like 7500 to our 7200 rev limit. So, aside from the aforementioned, and there being no emissions related stuff (or so I've been told), what are the differences between these two ECUs?

Hypothetically, let's say I intend to install one in my US '90. What can I expect to happen here? Starts, then stalls? Poor idle? Reliability issues? Explosions?

Ready....... discuss.

Also, please accept my apologies if this thread is in the incorrect section.

[— kung fu jesus —]

Barometric pressure is important for engines and altitude, particularly for air/fuel mixtures.

Why we have one and the Japanese doesn't, I don't know. I can only speculate it having something to do with our fuel, emissions, both, or something else.

I had one in my '92, and the only difference was the rev limiter and that it ran a touch leaner than the U.S. ECU the originally came with. Other than that, the car ran as it should.

[Rogue]

Isn't there some voodoo in the automatic 1.6 ECU?......been a while since I messed with smallblocks.

[Soledad]

I'd imagine so since the AT equipped 1.6L engines had cams with lower lift and duration than the engines paired with a MT.

I digress; it is my understanding that the Japanese cars had cams with a bit higher lift and duration compared to what our cars got. I have a custom ground set of cams in my car now. They're nothing too wild, and were made to be used with the factory valvetrain and engine management system solely for the purpose of reliability. I'd almost be willing to bet that I could use the B63H ECU with no issues whatsoever if I were so inclined.

[— Phatmiata —]

the Japanese also use a much higher grade of gas, when I was over there in 2000 I mostly saw 93 octane and higher, so im sure the computers are setup for the higher octane fuel, and also they did not have airbags, or airbag computers so that might be tied into the computer as well.

fwdtamiya was in Japan for a few years he might know about the gas, or Rod at Tetsuya can probably tell you the gas is a higher grade as well.

this is just my opinion though.

You can modify your factory ECU to run a higher RPM by overclocking the ECU and it will give you a 7650 RPM limit IIRC

[Soledad]

Oh, I know the fuel used in The Mother Country is a higher octane rating. FWIW, I exclusively use Shell 93 octane because of the cams I have installed in my engine.

[— kung fu jesus —]

Just an opinion, but if I ran custom cams, I would run an aftermarket ECU so I could maximize their potential. There are more options now and they have become more affordable yet easier to tune. I would include some dyno time too.

[Soledad]

Meh. I intend to keep it the way it is until the engine finally expires. At the rate it's going now, that will be a long time from now.