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This is a bit of a weird one. I recently saw an engine appear on Kijiji, it's a Series 5 13BT with auto transmission. Auto transmissions were never offered on a Turbo II, so it follows that it's out of a JDM model. I know they also got some different rear-end ratio options, a full-auto climate control option, etc. Anyways, something weird caught my eye:
What's up with that accessory mounting? High mount AC compressor, low mount power-steering pump? That's the reverse of all the brackets I've seen. Also, why make the change for auto models only (presumably), necessitating different AC and PS lines? Weird.
And then there's the 13BT auto. I don't know anything about automatic Rx7 transmissions, but I'm guessing this is a beefier version of the USDM auto. Otherwise I don't see it surviving long behind a 13BT.
Anyways, I don't expect answers to those hypothetical questions. Just posting in case anyone else finds this interesting
(P.S. The photos are crappy because they're screenshots, and I can't find the ad anymore so I can no longer get sharper images straight from the website. If I find the ad again, I'll update with higher resolution images).
That Accessory Bracket appears to be aftermarket. Both Sanden (North America) and NipponDenso (Japan) compressors use the same mounts, with the hardware running through the compressor instead what is alternator-style mount shown here.
As for the transmission and related hardware, it is the same as found on a North American car. N4A-EL if memory serves. This is just a hypothesis, but I believe in terms of auto vs manual transmission compatibility, the Japanese N318 ECU (September 1985 introduction) is akin to the North American N326 ECU (also September 1985). I'd have to dig through the RE-TECS manual to be certain though. The N319 ECU was introduced 1/1/1987, which follows the naming conventions for parts specific to an automatic but I'm not entirely sure that's the case for this. Both N326 and N318/319 were upgraded to N327 and N340 respectively on June 1st, 1987. The North American TII N332 ECU (introduced January 1, 1987) was upgraded to N333 at this time as well.
Somewhere in the middle of this, Mazda took the lessons and data from the Japanese Turbo FC automatics and applied it to the new HC Luce which was only available as an automatic. ECU is N336 (June 1, 1986), then N337 (December 9, 1986).
Auto FCs in Japan used the same diff housing as our TIIs, but with a 3.909:1 gearing. This means their driveshaft was exclusive to Japan only. It is similar to a Mazdatrix N/A trans to TII diff adapter driveshaft, but the length may be different. It may also help explain the apparent misinformation regarding driveshafts when swapping to a TII transmission. More info is in the Japanese Workshop Manual.
The Full-Auto A/C system was only on the GT-Limited Special edition. It works similarly to Ford's EATC system and served as the basis for what is in the Eunos Cosmo. The FD also had an optional full-auto A/C system too.
Looking at it I remember that some Sanden 701 compressors have the same mounting ears as the one in the photo. I was searching awhile back and found the same compressor was offered in different configurations.
Anyways, that makes me wonder if maybe it was a dealer-installed option. I know FDs had a factory AC option and a dealer AC option, so maybe there was a similar thing for FCs in Japan. I'd be surprised if there were aftermarket brackets and AC setups offered, since it seems like it would always be cheaper to just purchase the factory parts. And it seems to have required moving the power steering pump down, just to put the AC compressor where the power steering pump was. But then again, who knows?
Looking at it I remember that some Sanden 701 compressors have the same mounting ears as the one in the photo. I was searching awhile back and found the same compressor was offered in different configurations.
Anyways, that makes me wonder if maybe it was a dealer-installed option. I know FDs had a factory AC option and a dealer AC option, so maybe there was a similar thing for FCs in Japan. I'd be surprised if there were aftermarket brackets and AC setups offered, since it seems like it would always be cheaper to just purchase the factory parts. And it seems to have required moving the power steering pump down, just to put the AC compressor where the power steering pump was. But then again, who knows?
Negative on that. In Japan, they only received Denso a/c from the factory. Depending on grade and equipment, no a/c was available on S4 FCs such as the base GT model (MSC code F044-110). Can't remember if this reasoning carried over to the FD or not. But one thing I can say for certain is that the pictures you posted are NOT an original setup. Most likely a bodge-type repair using what the owner/shop had available to get it working again. The compressor looks similar to a 3rd gen Camaro compressor, also made by Sanden.
Anyway, going back to your original question. Japanese S5s all use N374 ECUs, North American Turbos are N370, N/As are N350. The EC-AT Control Unit is N375 and N351 respectively (Manual ECU number +1=automatic specific stuff)
While poking around in the final S5 Parts Catalog, I noticed something else that was kind of odd. The part number for the engine for the Infini IV is N384-02-000. Same for the Cabriolet with manual transmission, automatic one is N383-02-000. The rest of the Japanese S5s are all N374 (manual) and N375 (automatic). N38x is actually the European-spec S5 Turbo ECU prefix
