12a high RPM tips?
 

So I haven't been on here in awhile, as life has kept me from my project.
But I recently took my rotors, intermediate housing, and my Eccentric shaft to my local machine shop for some love.
The shaft was mint... It took a light polish, and was in great shape.
He cleaned my rotors for me, and pointed out some minor scuffing on the corners of each rotor.
He also found gouges in the housing from the corner seals.

Now this all cleaned up beautifully, and he did a bitch'n job lapping my housing. But he gave me shit for my build plans, as the motor was spun to hard.
In his opinion, this caused flexing in the factory stationary gears. Hence the gouges, and scuffing. But the bearings in the stationary gears were toast as well, which didn't help.
Basically he was telling me to scrap my parts list, and start over.

Now here's my deal...
I had actually planned on reusing my factory stationary gears. Then using the windowed bearings.
Do the hardened stationary gears really make that much of a difference when spinning the motor past 8k?

I have huge ports in mind, and was planning to spin the motor to around 10k..
I was gonna use the Atkins basic seals all through the motor, with the exception of the race bearings in both the stationary gears, and rotors.
The machinist suggested hardened seals for everything, and the solid corner seals with HD corner seal springs.

Would they really be necessary at 200hp, with those rpm's?
I worry about running hardened seals, cause they chew on the chrome so bad.
12a rotor housings are becoming extinct! I'd rather just buy new seals.. lol

But I could really use some advice on how I should move forward with my parts list?

it is always worth noting what the factory did, don't forget they went from 265ps@9000rpm in the race car, to 232hp@8500rpm in the street car in ~15 years.

anyways, Mazda went to hardened gears in the street car at 160hp/8500rpm (for the S5), so if you can find a set, you should do it. if you're willing to keep it to ~8000rpm, then the stock gears are totally fine.

a word here about the driving cycle, the race cars were running at 6000rpm+ for up to a day at a time, so its a very hard use-case. a street car is mostly under 4000rpm, with an occasional blast higher. with the race car you need to overbuild it and tune very conservatively, because its at its limit most of the time. the street car you can be less conservative with, because most of the time its just being a normal car. the stock gears will be ok with an occasional blast to 8500, but in racing you'd want to keep them to 8,000.

i would use all stock seals, except for the apex seals. again for racing, the solid corners might be a better choice, but you're not really making enough power. Mazda use the solid corner seals in the race cars, but in the street cars they never did, even the FD has the rubber type.

apex seals, i don't know. stock iron seals tend to not like high rpm (i'd keep it to 7k), the atkins seem to do better, and not fux0r the rotor housings. if using aftermarket seals you want to take the time and make sure they are all flat and not straight, and clearance them correctly.

if you can find a set the carbon seals are short lived, but really easy on housings, and fine up to 9k.

make sure you buy the FD oil pressure regulator, $30, and 110psi.

If you have that kind of build in mind I would personally do the following:

1. Blueprint and balance the rotating assemblies. RB or Mazdatrix can do this for you. $$
2, Hardened stationary gears and windowed bearings.
3. Modified oil pressure regulator and larger oil jets in the eshaft
4. FD corner seals and springs

Lapping your irons will likely cause them to wear faster now that the nitrided surface has been modified or removed. Just warning you about that.

Lapping is dumb. It was only relevant in the 70s before nitriding. But so many have had it done since then on newer irons.

Lapping a nitrided iron makes them so soft that you can literally leave an imprint with a ballpoint pen. Care to sign your autograph on the iron? You can even use erasable ink. The signature imprint will remain long after the ink is gone. :)

Thanx for the info everyone.
I've always wondered about spinning these to hard? But I'm kinda picking up that anything over 9k can cause damage?
I also never thought about that with the irons? That machinest never said anything about wear on it, and seemed to know his stuff. Thankfully I only did the one, and I have spares.. I'll save the lapped one for something else I guess.
But my biggest thing was those stationary gears.
So I guess I'll flip the bucks on those gears

Yeah don't believe the internet bros, these engines (12As) were designed from the factory to not exceed 8K and actually stop producing much more power after about 7K. To get more you need to port and modify the intake exhaust etc. To get higher revs (even more power) you need to start doing all we suggested. RacingBeat has some great articles online if I remember right that tell you these things and more.

I picked up on some mods, and the templates I have from pineapple racing are pretty wild!
I was gonna run the RB holly intake, and header. Along with some ignition mods.. I just wasnt sure if the hardened stationary gears were that important?
Their kind of expensive, so I was trying to save a few bucks.

I think my next engine will get hardened stat gears, but I plan to spin it up to 8k, with boost, and push it harder than my current floor-sweeper which I only ever pushed to 7k where it just started to run out of power. My porting is 74-spec which is larger than stock 12A spec, but smaller than pineapple. I would not want to drive pineapple racing ports on the street. I mean I could, as I've got an engine with that port size but I'm not going to personally bother with it. 74 spec really is the perfect port for the street.

I've heard a lot of opinions about streetable manners.
Lots of people run extended bridge ports, and p-ports on the street.
But.
Other than economy I don't see a big deal in huge ports. If the rest of the drivetrain matches it. I'm just doing a large street port.
I'm gonna run a low gear, and want a strong mid range to the top end.
Plus I do plan on racing it.... I would really like to land around the 200hp range.

200 to the wheels or crank? Big difference.

200 at the wheel is not uncommon.

SCCA Eproduction 12As make 200 hp on a street port with a 48 or 51 IDA webber with 42mm chokes.

Here are some bits from the Mazda Competition parts catalog circa 1999:
Mazda recomended hardened gears for 12As in racing environments. Their competition gear for the 12A was a modified 20B gear with a 3 window bearing installed.

Apex seals: Carbon apex seals and Iannetti Advanced Carbon seals are recommended for
any engine that will see 8000 rpm and above.

Bearings: 3-window type. Recommended for any engine used at 8000 rpm and above. Increases oil flow to the inside of eccentric shaft and to rotors.

They also recommended the larger oil pump from the 13B with hardened gears.

You want competition bearings in both rotors along with the main bearings. you want increased oil pressure and the oil jet to replace the check valve in the e shaft.

At the flywheel.

I'm not really sure what I wanna do anymore?
The more I dig into this motor, the more expensive things get.
I'm starting to wonder if the payoff is really gonna be worth it?

ive had some seat time driving a P port around in the last few weeks. if you spend some time tuning it, it actually runs fine stuck behind that Porsche Cayenne GTS doing 38 in a 65 zone.

the rest of the car matters though, the heim jointed suspension is loud, bumps hurt (solvable problem), its hot, racing harness are a PITA.

on the street, its a bit much.

on the track, the door handles scrape the ground, and its too quiet, the brakes are not great, and 130mph is probably faster than you really want to be going, and it needs more power

what do you win if it makes 200hp?

we've noticed that fun actually correlates more with perception of speed, than actual speed. (actual speed correlates more with money invested in the car, if you took a Maclaren and a rental car to the track you would be faster in the rental car, by a lot)

when a car makes a cool noise and feels fast, its fun. when a car is fast but doesn't feel fast, its boring. my friend had an AMG Mercedes, and it sucked, it felt slow, ride was bad, the non AMG was better, it felt slow too, but at least it was a nice place to be.

i know its a bit James May, but a decent suspension and a street port would be fun in an SA/FB, its also fairly simple, and inexpensive

Well I was planning to drop this into a 78' Datsun 510 wagon.
The car weighs in around 2300lbs, and has a solid rear axle on leafs.
I had a game plan to just make it a fun cruiser, with stupid low gears.
But for the money I would invest into a 12a swap for 200hp, I could do a vg30e swap way cheaper with close to the same power numbers. Then I'd also have money left over for a power adder, with a more reliable/efficient bullet..
I just keep trying to weigh out my options?
I love rotary's. But a 13b is way to expensive, and the 12a might not cut it?
I appreciate all the info tho.
thanx

if it helps, piston engines are lazy, if you had a 200hp piston engine next to a 200hp rotary, the rotary will run away and hide

At that weight a stock 12A with a massaged nikki or weber intake and a full SP RB exhaust will be a very fun cruiser. Port and it gets more fun. You don't need to rev it out above 8K either. I don't understand the reasoning on the gearing either but the 12A and its transmission will probably almost bolt up with minor fab into that 510. You could use the 510 rearend with a custom shaft.

What I posted is what you want if your motor LIVES over 8000 rpm. AKA race car.

Your standard 12A will still last a long time with occasional blasts past 8000. A good street port, good exhaust, and good intake will make 130-150 hp and will give you years of good service.