www.RX7fb.com

I think the S3 designation comes from the UK where we never got the different GS, GS-LE model differences. So yeah, I believe the Series 3 title relates to all 84, 85 cars. But only relevant to the UK...

What did you get for 84-85 then? Surely not every S3 rx7 got the 13b like only our GSL-SE did. I guess the only thing I'm trying to verify is that a US 85 GS has a 26-spline.

Edit: Upon review, it appears only the US even got the GSL-SE with the 13b. Which assures me that any mention of the S3 on international forums relates to my car.
Didn't know we were the only ones to have a fuel injected first gen.

We never got any 13Bs in any RX-7s until the FC! 12A naturally aspirated in everything. The UK models tended to be a sort of mix and match of trim levels from other markets, so got almost everything except leather, aircon, 13B injection, and LSDs but there was no option to spec them up, what you saw on the dealers' floor was what you got

You weren't the only ones to get a fuel injected FB....The JDM 84/85 12A Turbo was also fuel injected, and was 165hp vs. the 135hp in the 13B GSL-SE.

S3 really indicated the body styles, which in the rest of the world is reasonably clear cut but not so much in the USA. The 84/85 GS appears for all intents to be an S2 in our eyes. It has the S2 interior, the S2 dashboard and the S2 4x110 wheel pattern. I purchased some 85 rear discs when I was last in the US, and discovered they wouldn't fit my 85 S3 (12a).

I would be careful when picking parts for yours as I am sure some of the 'S3' bits may well have made it into your car - I have a feeling the larger 26 spline rear end was one of them so the diff compatibility is the same as S3, but the brakes and stud pattern and alloy wheels are what we think of as S2. The S2 has a different wheel offset, and therefore a narrower rear end and therefore shorter axles so these parts are surely S2.

Perhaps you will be able to confirm this for us and others who might be in your situation? Tricky to tell without pulling the diff out though.

If the deal goes through on this Torsen I'll probably buy it no matter what. If I can pick it up for $200 and they sell for $500 minimum on ebay it shouldn't be too much of a loss either way.

I guess at that point I'll pull my diff out and see what I find. No outside indicator of 26 vs 24 spline, right? I know some had heat fins on the pumpkin.

Our external indicator is the PCD. Ours diffs are all 3.9 ratio as well.

Backtracking a little - the dash was updated in all LHD drive cars to the squarer design with dials for the ventilation and non central tacho.

The front bumper has the lower cooling vents and the 12a also received the 'beehive' oil cooler like the S3 we know here.

You really have no idea where to start when trying to nail down which bits are which - are they S2 with updated bits tacked on, or are the S3 with some bits regressed to the previous model? Why they didn't simply have the same LHD market 12a version I have no idea - the cars that were sold in Europe were all but GSL-SE apart from the engines and some features like LSD - maybe PAS? certainly some had AC. Maybe they thought the engine alone wasn't enough of a differentiator and wanted to show case bigger brakes and a more common PCD in the mix? Still seems odd.