inittab

When the RX-7 first came out I was a little surprised to learn that Mazda put the old 12a in it. Okay granted I know it's not really the "old" 12a, it's actually quite a bit different than the 12a of the RX-2 and RX-3. At the time the RX-7 came out, however, Mazda already had it's two feet firmly planted in 13B territory with the RX-4, Cosmo and REPU, so I wonder why they downsized again. Just curious if anyone knows the answer.

onepointone

actually, thats a really good question

MikeLMR

the oil crisis ?

1rx7owner

maybe they thought better emissions?

82streetracer

iTrader: (1)

name a car company that puts the same engine in every car.

MikeLMR

Delorian

rotary emotions

Mazda put the 12A in the seven because it would made the car cheaper! At that point they were very close to being bankrupt ( alot of unsold RX3's and 4's) and the new car had to save the firm. So it needed to be as cheap as possible, without becoming bad quality of course. That's why it doesn't have rack&pinion steering, no power steering, no independant rear suspension, and no 13B. It even had drum brakes remember?
But it did the trick: being cheap and good it sold very well, and saved Mazda (for a while). So later it did get some goodies, like disc brake all-round, powersteering option for the GSL-SE, and 13B power for that same car.
Also, having a smaller engine ment more potential customers ( some countries have huge road taxes).
For example the Belgian road tax for a 13B 2nd gen: $500, for a 12A less then 350. Makes sense to get the smaller engine...
Now the RX7 became a full sportscar, the taxes don't seem to be important. A FD costs you 1000 euro a year overhere!

inittab

Follow the money......

Cost seems to be a reasonable explaination. Well I guess if you're almost bankrupt then every penny counts. I wonder if they had a surplus of 12a parts or something which made the decision even easier. Honestly though, how much less would a 12a cost over a 13b? Can't be much! Mazda already had the tooling for the 13b so that couldn't have been the issue.

85RX7GS

iTrader: (1)

Actually, Mazda took the old 13B of the '70s off the market because of poor reliability with the seals. The 12a has proven it's reliability so that went into the 1st gens. The improved 13B came back in the SE in 84.

85RX7GS

iTrader: (1)

Also, the idea behind the Rx-7 was an affordable, yet high-performance sports car.

inittab

But the seals in the RX-7's 12a are dramatically different from the early 12a's. I'm not so sure I can totally buy that argument.

85RX7GS

iTrader: (1)

Yes, but from what I've read, the 13B was pulled away from the Rx-7 because of the issues with it's reliability.

CHEF_EG_1

haha... the loophole.


it's said that for every 55 words, there's at least one loophole. before MikeLMR's post, there were exactly 110 words.


good call mike.

error402

Do the earlier 12a's have the 3 mm seals as they do in the 12a's for the RX-7's?

-Error402

inittab

The early 12a's had larger "carbon/aluminum" composite apex seals, I think they where 5mm or 6mm thick. They also had dual side seals. If I remember correctly, that was how the early 13b's where designed too. It's been a long time since I cracked one open.

Acuspeed

I can buy the cost factor on some things, like the recerc. ball steering, solid axle rear end ... but not for the motor. The reason for this is the multitude of changes that the 12a underwent as installed in the early 79's. I'm no expert, but I really don't see why updating the 13B would have been anymore expensive at that point, unless, for some reason, the parts cost going into it would be more expensive.

If I had to guess, taking into account that this car made it's debute into a market that was skitish of big motors and the fuel they promised to eat up, as well as one that was likely skeptic of performance vehicles in general, again owing to the muscle car era and fuel consuption, that Mazda choose the 12a due to slightly better fuel economy.

In a way, it fits. I mean, if you look at the primaries on the stock Nikki, they are also tiny, and we all know that it's the 3rd largest restiction to the motor after exhaust and fuel delivery, and also the key to developing much more than 140 or so hp w/the 12a. It almost seems, at least to me, that Mazda was trying it's best to give the most fuel econmy they could at the time.

Of course, this leads to other questions, including the one that baffles me the most. Why introduce the car with a points ignitions system, only to replace it the following year with an electronic unit, which istelf was replaced a year later with yet another version with the ignitors on the shaft rather than in a separate box ... very interesting questions indeed ...

WackyRotary

I think we ALL know the REAL reason they put in a 12a instead of a 13b 4port in 1979: The 12a takes less aluminum to build!!! LOL!!!!!! The 20mm extra thickness was too much for mazda to invest in the car to sell it were they wanted to sell it at and attract buyers.

On a more serious note, I don't really know! I am certain a 13b 4port designed the same a 12a for '79 would of been 130hp in all stock form with the same emissions and a very mild drop in mpg. BuT anyhow, its part of history, it can't be changed, ofcourse, it would still be nice to hear what mazda has to say about that.

OtakuRX

iTrader: (1)

I think I heard something about power to fuel ratio, and that the 12a had better mpg for hp then the carbed 13b, and emisions played a part too, but there was an oil shortage when they first came out. That is how come alot of cars from those years under went some drastic fuel changes.

RotorMotorDriver

iTrader: (1)

Technically not true. Like the 2nd gen RX-7, they had a turbo version, and a N/A version .

~T.J.

wam

but really i was in a delorean club for a while..i also had many of these...turbo was a aftermarket add on on the PRV V6 that went into that car!

357

Here's my theory, in addition to the cost/simplicity side:

With a 12A, I believe the 1st gen is balanced perfectly 50/50 front-rear, which gets upset with the heavier 13B/EGI setup.

That's my $.02

MikeLMR

I was thinking about this the other day ... Mazda claims that all of its 1st gens have near 50/50 weight distribution .... what did they put in the back of a GSL-SE to balance it out over a GSL ???? also my car and many others outside the states have a rear seat (as they were designed to have from the outset) so what did they take out of the front or add to the back of the US models to balance it all out ? ?

rotary emotions

Don't forget that the 1st gen was a world car, it had to be sold everywhere. (while the 2nd gen clearly is more USA-styled) This means the car had to be affordable on many markets. Fuel is very expensive in Europe, about $1 per liter on the mainland, even more in the UK. Back then it wasn't priced at $1 of course, but you can see the difference with the rather cheap US prices... So every extra mpg was important. Also a carburated engine is simpler then a EFI, so that's another reason.
And, as mentioned before, taxes will have played a big role...

85RX7GS

iTrader: (1)

Wasn't the old 13B carburated at the time?

WackyRotary

I still haven't heard a reason to me that justifies 12a over 13b. That weight comment doesn't really ring true to me since a 4port 13b weighs so little more then a 12a, its not even funny. 20mm longer overall! ...just 20mm more rotor, e-shaft, housing, that can't weigh more then 20lbs? Oh, and slightly longer intake manifold, tenson bolts, and exhuast manifold! Whoopy doo! There is only one explaination I could believe, and that is mpg of a 4port 12a is apparently better then a 4port 13b equivilant. Anyone else got a reason that could make sense?