BicuspiD

As far as I can tell, all SA had 12A, 4 lug wheels and drum brakes in the rear - is this accurate? What are the specific differences?

faye x7

http://www.rotorhead.ca/ref_beginning.php

peejay

Did someone mention SA's?

There are many differences between SA and FB.

For reference, SA means Series 1, and FB means Series 2 and 3. I am ignoring the GSL-SE for simplicity.

Starting with the body, the bumpers are obviously different, SA having metal-skinned bumpers and FB having plastic-skinned "smooth" bumpers. This also means the front fenders are different. The rear taillights are smaller on the SA than the FB, same height but a few inches shorter width-wise. The rear panel is different also, obviously, since the license plate mounts in a big indentation in the back between the taillights, while the FB has the finishing panel between the taillights to make it look like one big taillight assembly, and no visible indentation. (There *is* an indentation if you remove the panel, but it is nowhere near as large as on the SA) And of course the rear license plate mounts under the bumper instead of above. SA's had a little "Rotary Engine" badge in the indentation.

Looking in the bodyshell, SA's had a deeper spare tire well. All SA's came with full size spares with a normal tire. In addition, SA's with aluminum wheels came with an aluminum spare. FB's went to a thin temporary spare so that the spare tire well could be shallower, so the gas tank could be larger. US-market SA's (maybe Canada too?) had big beefy braces between the behind-seat crossmember and the rear springs. This was for rear-collision performance. Mazda found that it was not necessary, so FB's had the bracing eliminated, so you could find 4-seater cars in North America. The two seat FB's all had storage bins behind the seats, while SA's did not, just the sheetmetal cover with carpeting over it.

Wheels and suspension: SA's had either steel wheels or waffle wheels. The waffle wheels require special longer lug bolts since they are MUCH thicker in the middle. They also have inserts where the lug taper is, they appear to be steel. I don't know if FB's had steel wheels, I've never seen one with them, but the aluminum wheels ("cross" wheels) have a thinner section and use normal short bolts. All wheels were 13x5.5 (except for the '83 LE which had 14" wheels) and had the same offset (+25mm) and bolt pattern (4x110mm). The rear sway bar was only on GS models in '79 and on all models in '80, and was 18mm in diameter. FB's all had a 15mm (half as stiff) rear sway bar. Front suspension is the same.

Brakes: '79 had "wedge" type calipers, '80 had the same design calipers as '81-85. However the hydraulic thread pitch is different: SA had a weirdball thread pitch (on ALL hydraulic fittings) while FB had "normal" metric threading. The calipers will physically interchange as long as you allow for the thread pitch differences. For the rear, SA had non-servo, manual adjusting drum brakes. Each individual shoe had an adjuster on the bottom on the backside of the backing plate. FB's had a more "normal" self-adjuster mechanism, and of course the GSL models (FB only) had discs.

To be continued...

Siraniko

iTrader: (13)

I will buy SA anytime. Big weight difference between SA and FB except FB has a better interior. All other FB stuff (mechanical/suspension) can easily be transferred to a SA.

I had a 79 and 80 in the past. I only bought my 85 GSL for the interior and original blue paint with few dings and slight fading in the roof. Otherwise, me is SA all the way.

peejay

Engine and emissions: Now we're getting into the BIG differences. All SA's had thermal reactor emissions systems. How this functions is basically the engine runs rich under all conditions in order to keep the exhaust manifold (thermal reactor) fed with HC's and CO. The air pump pumps air into a heat exchanger (the converter-looking thing next to the transmission) where the air is heated up, and then it travels up the outer layer of the double-walled downpipe. From there it goes through a hole in the rear rotor housing, sealed by the exhaust manifold gasket, and gets distributed to the air injection holes in the exhaust ports. The hot injected air reacts thermally with the pollutants (IE it burns them!) and does a remarkably good job of cleaning the exhaust. This of course requires that there's a steady supply of HC and CO, to make sure the burn never extinguishes. To this end, the emissions computer shuts off the trailing ignition under certain conditions. Sounds backwards, intentionally making the engine run dirtier to have good emissions, but that's how the TR system has to work. The TR can get REAL hot, so it has a cooling jacket around it and the ACV can shuttle air from the air pump to the cooling jacket to keep the TR cool. The air coming out of the cooling jacket goes to a small, maybe 1" pipe that runs to the back of the car alongside the exhaust system.

The FB system is completely different. For starters, Mazda eliminated the thermal reactor, going with a standard exhaust manifold and... catalytic converters. Catalytic converters have a mesh brick or pellets coated with a catalyst that will combine HC and CO with free oxygen (aka burn them) and some catalysts also reduce NOx to N2 and free oxygen. So what you want going *to* the cat is a "stoich" mixture of unburned fuel and uncombined oxygen. Rotaries don't like running at stoich under many conditions, so they need an air pump to provide the extra oxygen. The ACV routes air either to the converters, between the precats and the main converter, or to the exhaust ports, depending on conditions. The way the injected air gets to the cats is entirely conventional with hoses and check valves to prevent exhaust gases from traveling upstream. The way injected air gets to the exhaust ports is entirely different from the SA: The ACV sends the air through a port in the center housing, sealed by the intake manifold, where it then gets distributed to the exhaust ports. SA's don't have this port, which is why when you put an SA intake manifold on an FB engine you need to creatively block this port off somehow. So why would you put an SA intake manifold on an FB? Mazda introduced a little device with the FB called a shutter valve. Rotaries tend to buck at low engine speeds and high manifold vacuum. The bigger your ports/more overlap you have, incidentally, the lower the vacuum threshold becomes, until the engine is bucking even at idle - brap brap brap! Buck back to the stock vehicles: The shutter valve literally shuts off air to the primary port of the rear rotor, while simultaneously shuttling raw air (from the air cleaner) to the secondary port of the rear rotor, when decelerating, to eliminate the bucking. Result: Lower manifold vacuum, meaning no more bucking, and the rear rotor doesn't get any fuel, so the engine is still decelerating the car instead of accelerating. Note that Mazda COULD NOT have used this with a thermal reactor, since the lack of unburned fuel would have caused a "flame-out" in the TR.

Ignition system: '79 had points, '80 had electronic ignition with the ignitors mounted to the driver's side strut tower. FB had electronic with the ignitors mounted to the distributor, where they overheat and like to fail. I have never heard of an SA ignitor failure... but that could also be because there are scads more FB's out there than '80s. Again, from above, the SA had a part time trailing ignition, so the tach signal was recieved from the leading coil. FB had full time ignition, so they moved the tach pickup to the trailing coil, probably so that people would know if the trailing ignition died. Also, FB's controlled the fuel pump via tach signal: If the emissions computer saw that the engine was off (no tach signal) it would shut off the fuel pump relay. That's why when your FB's trailing ignitor dies, first you have no tach, then a minute or so later the car stops running because the fuel pump was shut off. SA's had full time fuel pumps, when the ignition was on, the fuel pump was on. Period. Just hope that if you get in an accident and the fuel lines get severed, you remember to shut the igniton off so that the fuel pump stops gushing out onto the ground... the reason why FB's (and all cars with EFI) kill fuel pump power when the engine dies.

Gauges: SA had nice green gauges. Five of them. Fuel level and temperature on the left, speedometer (130mph or 85mph) on the right, and a tach/voltmeter in the middle. When the ignition was on and the engine off, the tach acted as a voltmeter via a second set of numbers in the middle. Neat setup. Note: no oil pressure gauge. Not even a low pressure idiot light. SA engines were not even drilled/tapped for a pressure sender, and there is no boss for one. All you had was a low oil level idiot light, which would come on when the engine was three quarts low. FB's had a full complement of gauges, including an oil pressure gauge and a separate voltmeter, and orange or red lighting depending on S2 or S3. S2 had a very SA-looking gauge set, while S3 (US market) had, as Monty Python would say, something completely different.

To be continued...

peejay

Transmission/driveline: Ignoring automatic transmissions, since I have no experience with them, and nobody seems to care about them anyway. (I doubt there were many differences, since Mazda used the same JATCO automatic from the mid 70's up to, well, up to the end of the S4 models. The 4 speed was a 3 speed with an overdrive unit sandwiched in the middle) Mazda started using the "smoothcase" 4/5 speed starting with the first RX-7, still uses it in the Miata, and has used it in all RWD applications except for V6, 2.6l truck, and turbo FC/FD. They have made many little improvements along the way, playing with replacing circlips with nuts, changing bearing designs, changing gear tooh pitch, etc, so many of these internal changes cannot be classified as SA or FB specific. For example, Mazda switched from holding the shift fingers to the rails with bolts, to holding them on with roll pins, a few months before the end of the SA run. Does that count as FB specific? I say no, because there were plenty of SAs (mine included) that had roll pins. That would be one of Mazda's running changes that plays hell with the parts cataloguers. BUT there is one dramatic difference between SA and FB: The shifter! The SA had an integral shifter, mounted directly into the tailhousing, and a long double-bend shifter that had excellent placement. The FB had a remote shifter, mounted in a pedestal *behind* the tailhousing (over the front U-joint!) and a much shorter, stubby shifter. The shift ***** (which are different thread BTW, 10mm on the SA and 12MM on the FB) are about the same distance from the driver, and the shift *throw* is about the same, since the SA lever is also longer beneath the pivot, by about a quarter inch. But the *height* is a lot different. And because the below-pivot distance is shorter on the FB, for the same amount of shift travel, the FB shifter changes angle more than the SA shifter. It's a matter of preference, but my personal feelings on the subject are well known. (IE: Dammit Jim, I want a shift lever, not a light switch! Or: If I wanted to have to reach *down* to the shifter, I would have bought a truck)

A pictorial explanation is available at http://www.geocities.com/izzmus/trans/trans.html but be forewarned: My website has limited bandwidth and only 3 or 4 people per hour can view the page before I go over the limit.

The clutch master cylinder and slave cylinder are identical except of course for the differing thread pitches on the hydraulics. (Yes I know '83-85 12A had a different slave, that's because they repositioned the bleeder due to the beehive oil cooler)

What else am I missing.... There were numerous differences between SA and Series 2 interiors, but then again there were also numerous differences between S2 and S3, so I wouldn't classify them as SA vs. FB but more like S1 vs. S2 vs. S3. One thing to note is that the headlight and wiper switches are reversed on the SA. The left stalk goes up and down for turn signals, and back and forth for high beams/low beams/flash... but you twist the end to turn the wipers on and off. The right stalk is the headlight control - up one notch for parking lights, up all the way for headlights. Completely backwards from the way everyone else does it, but That's Okay.

BicuspiD

WOW peejay thank you

I had no idea there were so many subtle differences in the chassis/equipment

rotary emotions

I didn't read all of this, but just want to add that I believe you're only talking about US models? In Europe S1 were SA, but S2 still have SA chassis number, although they are basicly the same as your FB's S2...
We got S3 as FB chassis number (VIN?) but no GSL-SE, yet our FB's did have the uprated dash, brakes, suspension, ... Count to this a few US-imported models, and it get's really confusing overhere

bliffle

The 79 SA had points ignition, just like my REPU, so what spark plug works best? I believe that points system requires a gap of about .025 and electronic about .050 (and this is probably the factory gap on the BR8EQ14s, etc.) So the REPU and the 79SA oughta use the same plugs.

So what plug is right?

B

bliffle

Gotta be something other than BR8EQ14, right?

B