Questions about building 12a
 

I'm doing my first 12a rebuild,
I have a 81-82 model 12a.. and I understand these have the heavier rotors
I'm looking to upgrade to the 83-85 lighter ones.. but I'm not sure exactly how..

I plan to get a lighter flywheel too.. do I buy this stuff for the 83? or the 82?
What about counterweights? 83-85 rotors.. 83-85 light flywheel.. 83-85 counterweight??

:Wconfused

Any help appreciated!

i am not sure exactly but we need a damn faq on this. gets asked alot!

yes..has to be a matched set of front weight/rotors/flywheel(or rear weight/aftermarket flywheel)

all of those components must be intended for the same weights in order for the assembly to be balanced.

With 83 rotors.. as for rotating assembly.. I buy everything just like i have a S3 12a?

Seems simple enough.. .. Do i need a new front counterweight?

counterweight has to be the same year/series as the rotors and flywheel.

if your rotors are lighter than what you started with, then your front weight and flywheel need to be as well.

unless you get the auto flexplate/flywheel thing and an aftermarket flywheel

I think you mean the auto counterweight which still needs to match the rotors you use. The flexplate goes in the nearest garbage bin,

Let's keep things simple. As the rotary engine developed and aged, the clutches and rotating assemblys followed. From the R100 though to and including the '83 RX7's, all clutches were 215 mm. From '84-92, all NA clutch assemblys increased to 225 mm in diameter. All turbo engines, along with the RX8 had 240 mm clutches.

E-shafts and aftermarket flywheels are all neutrally balanced, meaning neither affects the balance of the rotating assembly. In stock form, the front counterweight and the rear counterweight built into the flywheel balances the rotating assembly, in relation to the year/weight of the rotors.

If you wish to upgrade to a lighter rotating assembly, you will need an S3 front counterweight, an S3 rear counterweight from and auto tranny and a matching pair of S3 rotors that have the A-E letter stamp within in one another.

I would make the decision after you tear things down. If your housings are no good you might want to consider doing a 13b conversion. If your housings and rotors are excellent than all the money spent to lighten things up makes only a marginal difference. Those funds would be better spent upgrading your carb to a sterling, getting a free flowing exhaust, upgrading the ignition and doing some porting.

I already tore down my 12a, and the housings were toast.. but I've already bought some excellent condition ones and would like to go through with the 12a build.. with porting of course
My rotors are fine.. but they are heavier, so thats why I'd like to upgrade to S3 lightweight ones.

Trochoid.. I need to get the counterweight from an auto tranny? to put on my manual car? That seems kind of odd..

The rotors should not have matching letters? My rotors have A in one and B in the other.. and I don't understand why

the letter designates the weight of the rotor, matching is ideal, but within one letter of eachother is acceptable

if your going to do that minor up-grade you have to use the whole assembly from front to back..

front balance
e-shaft
both rotors DON'T MIX THEM!!!
and rear balance with flywheel...

after that your golden

oh shit don't forget about the marking of the letters... make sure there within one letter of eachother for best results and balance...

There is no difference in the eccentric shafts.

:wink: Hey thanks for the info, I'm about to do a 12a rebuilb soon.

Trust me! spend the money elsewhere and keep you rotating assembly including flywheel. I speak from personal experience. I just rebuilt my 13b and went from the lighter S5 rotors and flywheel to the heavier, stronger s4 rotors and flywheel. I actually like and notice the weight difference. Better launch, even on light throttle and better cruise which really helps my bridgeport. Just "my" opinion, but how mnay bridgeports (1/2 bridge) can cruise down the road in 4th at 2000 rpm?????

Probably only yours. ;)

As for stock or streetports, you want a light steel flywheel. Or if you really like playing with the clutch pedal a lot and don't mind bumper to bumper traffic, and don't have many hills nearby, perhaps an aluminum flywheel is for you. Do yourself a favor though and start with light steel. I did and found it to be too heavy with my Camden so I just swapped in an aluminum. The Camden's extra rotating weight made the light steel feel heavier than it should so I'm hoping the aluminum will feel more like a light steel. Just waiting for some sealant to cure and some drier weather.

If you want another opinion on light vs stock flywheels, PercentSevenC has also experienced going from stock to light steel to a superlight steel which is something that weighs about the same as aluminum and he loves it. He even once said he couldn't live without his light steel.

To each his own...