12a mazda rotary conversion

[bajabugman66]

Today marks the start of my Rotary conversion. Went into town and picked up a mazda 12a engine from a wrecker. Guy said that it ran great and it is all complete. I went with the 12a because its carbed and only a couple wires to run.

_________________
Im like a moderator with no real powers or motivation.

66 baja-rotary powered \=O=/

Oh I get it, the robot doesn't have any arms!

[BigTex]

Good luck with that. My friend had a 2 mazda's and they both had rotary's which had crapy wiring and caught bothj cars on fire. I guess it's a good thing you got the one with fewer wires.

[thudknuckle]

woooo hoooo some one else is coming into the rotary scene ,, looks like you got a single dizzy model wich is a good start ,, even though 12a dotn have all that much low down torque as a 13b ( carbied and then injected has alot more) the single dizzy models have almost double the low down pull of the older twin dizzy models ,,, i big advantage of the 12a however over the 13b carby is that they like to rev out alot quicker and will go further on the revs more safely then a 13b.

and more details on the rotar ?? stock porting ??,, looks like a great project ,, here is my website that might help you out in regards to cooling , radiator setup , exhaust ect ect , it may be a 13b injected but the principle is there ...

ooo im so happy some one else has seen the rotary light ,, all thebest with teh project

[SSChicken]

may have missed it, but i think you forgot your website link

[bajabugman66]

The engine is as stock as they come right out of a 1980 rx-7. Im really thinking of ditching the stock carb and going to a 48 idf instead.
Im not sure my rad will cool the engine though, i guess theres only one way to find out. I will need an oil cooler will I not? Any ways i've still yet to order an adapter but theres still work to be done before im ready for th engine. And a custom exhaust is going to have to be built because i dont want the stock air pump or the thermal reactor.

thats about all i got for now.

CAs
_________________
Im like a moderator with no real powers or motivation.

66 baja-rotary powered \=O=/

Oh I get it, the robot doesn't have any arms!

[Jeff20B]

You've been mislead by the wrecker guy. It looks like an '83-'85 12A. How to tell? It has a beehive oil cooler thing under the oil filter, the distributor is the '81-'85 type with the ignitors on the dizzy housing. It has an exhaust manifold. None of these were on an '80 engine.

Rejoice! You actually have a better engine sitting there. If it is indeed an '83-'85, it has the lightest 12A rotors Mazda produced for the 1st gen RX-7, the distributor is more compact and works better in my opinion, you already HAVE an oil cooler sitting right on the engine. I'd suggest using it because it can turn out better for baja use than an air oil cooler since there will be no need for small electric fans (they're always inadequate), no need to find a good location for it, no need to run custom oil lines; saving money and time, no chance of them getting ripped off while offroading etc. My friend's baja switched from air to a beehive and it works a lot better. I plan to use a beehive on my baja project as well.

I suggest keeping the stock carb and doing a rat's nest removal. Also remove the shutter valve (flapper valve) in the manifold. You'll get the best torque a 12A has to offer. Much better than an aftermarket carb. It's basically free too (just takes time and a little patience, which I'm sure you're full of taking on a project like this hehe). Especially since you don't plan on tearing the engine down for a port job any time soon.

You can either:
A. leave the carb and manifold stock and just remove the rat's nest
B. take the manifold off the engine, seperate the carb from it (much easier off the engine), remove all emissions from the carb, simplify the choke (or remove it completely in your case), swap in a couple slightly larger primary fuel jets (suggest 95 for stock ports), increase accel pump shot and duration, remove shutter valve from manifold, cut channel to mimic other side, remove ACV and replace with a block off plate, block off some of the nipple on the carb spacer while keeping one or two open for PCV (positive crankcase ventilation) and possibly distributor vacuum advance.

I suggest B. For details, read these:

Carb and manifold mods.
http://www.rx7club.com/forum/showthread.php?t=637323

The car these modded parts went in and the (favorable) result.
http://www.rx7club.com/forum/showthread.php?t=638282

A recent thread about PCV
http://www.rx7club.com/forum/showthread.php?t=642160

Please follow any other relevant links found in those threads for more info on the subject. Especially Sterling's Nikki mod thread and the rat's nest removal thread.

By the way, that experimental engine is all together and in the project car. If it runs as well as I expect it to, I'll take what I learned and apply it to the baja engine. Would you guys like me to start a thread here detailing the build? It's more work for me so I won't bother unless you'd find it helpfull.

[runslikeapenguin]

i really want to get a rotory to start expirament with, its onething i have no experiance with
_________________
never forget 1-31-07

[72BajaBen]

what year and model did the 12a's come out of?

[Skidmark]

1979 thru 1985

Another rotary tip is to remove the oil injector system, it's inadequate for off road or racing abuse. You will need to make a block off plate for the case, plug the fittings on the carb, and run 2 stroke oil in your fuel. Your seals will last longer this way.

My 12A experience... #38 lifting the inside front wheel in turn 4 at Willow Springs.

_________________
"It's not complicated, it's just expensive!"

WARNING! This person has been consumed by the Dark Side.

www.socalbajas.com

http://i135.photobucket.com/albums/q148/bajaskidmark/SCBaja.jpg

[bajabugman66]

mixing two stroke gas is a pain in the ass and i wouldnt know what to mix it at, its going to be a daily driver and weekend playmobile so it should hold up alright.
_________________
Im like a moderator with no real powers or motivation.

66 baja-rotary powered \=O=/

Oh I get it, the robot doesn't have any arms!

[bajabugman66]

I gotta work tomorrow (at our FLAPS). What do I need to tune up and help it perform a bit better.

- Plugs
- Cap
- Rotor
- Plug wires
- umm some sort of after market air filter
- A tach to watch those RPMs
- anything else i forgot?
_________________
Im like a moderator with no real powers or motivation.

66 baja-rotary powered \=O=/

Oh I get it, the robot doesn't have any arms!

[cobhc619]

_________________
1970 Baja
1973 Westy

[Jeff20B]

You'll be fine with the stock oil metering pump. Maybe you could jack it open a little with a couple small washers near the bottem of the rod. I'm doing that with mine.

For plugs, it depends on which ignition system you use. If stock, use BR8EQ-14. If you go with a popular direct fire ignition system on leading, such as DLIDFIS or 2GCDFIS, get the 2nd gen BUR7EQ plugs. Leave the trailing plugs stock BR8EQ-14 since they'll still be fired through the cap.

Cap and rotor could be Bosch or whatever.

Wires can be NGK. Some have had trouble with MSD brand wires. I tend to use NGK and they work fine.

Air cleaner assembly? Racing Beat sells a nice spun aluminum one that looks and sounds cool. I might get one for mine. The filter can either be stock or their foam one.

Get a regular aftermarket tach that reads up to 8k. Set it to 4 cylinder mode. Hook it to the trailing coil (negative side) so you'll know if the trailing ignitor ever dies (it adds no power since it was for emissions so you'd never know whether it was functioning otherwise). Just FYI: don't exceed 8400RPM because engine damage will occur. It needs to be built to handle high revs safely. An occasional blast up to 8k is ok, just don't hang out up there.

[thudknuckle]

with the oil metering pump i would highly recommended checking all the little oil lines to make sure non have little cracks or are really brittle, as this is a problem i had , as i had to replace all of them. i really considered goin premix but i didnt likethe idea of messing around when filling up so i replaced it all ( beware in australia i had no choice but to pay 170 - 220 EACH for the little plastic lines ,, rip off i know but thats all i could get )

as for the oil cooler the beehive is great , i really want one so i can adapt it so i can run both a bee hive and my setup now in line, extra cooling ) ( i have an oil cooler mounted behind the rear engine cowl where the air has no choice but to be forced though it )

MY WEBSITE WITH HEAPS OF PICS AND INFO - http://groups.msn.com/GottaVW

not that i know all to much about the carby side of things as all my work was injection based on the rotary but talking to a few rotor mechanics i was told that a 52 ida webber on the 12a would provide the biggest bang

hope this helps im sure my website will help out with alot of questions as i spent months goin through all the problems and my setup is working beatifully cops a beating and yet is daily driven every day for at leats 1.5 hours in traffic and highways use with out any signs of engine problems ( not to mention the offroad fun it sees)

[HAJA]

A few useful websites
www.atkinsrotary.com
www.mazdatrix.com
www.racingbeat.com

[HAJA]

1 more..
http://www.rx7club.com/

[bajabugman66]

Ya I will be replacing those little lines, i looked at em and they are pretty much gone but thanks for the heads up. Im a little confused on the rats nest end of of things because the distributor is hooked to it. If I take the nest out do i just run a line to the carb in place of it? Also it looks as though the rear seal is in need of replacing. But other than that the housing doesnt appear to be leaking anywhere. Now, im not anywhere near starting this thing so any procautionary measures I should take when doing so eg. (babying the engine for a bit, changing the oil after doing that) that whole chestnut?

CAs
_________________
Im like a moderator with no real powers or motivation.

66 baja-rotary powered \=O=/

Oh I get it, the robot doesn't have any arms!

[bajabugman66]

Well the manifold is done! and I cant find my camera to show you guys, damn
Gave the intake a bit of a polish and the block off plate is on. Time to move on to the carb.

yup, moving along


CAs
_________________
Im like a moderator with no real powers or motivation.

66 baja-rotary powered \=O=/

Oh I get it, the robot doesn't have any arms!

[bajabugman66]

Manifold mod done, looks about even.

_________________
Im like a moderator with no real powers or motivation.

66 baja-rotary powered \=O=/

Oh I get it, the robot doesn't have any arms!

[Jeff20B]

That channel looks pretty good! Be sure to leave the runners a little rough. Don't try to smooth the stock sandcasting finish. The little bit of roughness is to help with laminar flow and prevent fuel wetting during quick stabs of the throttle. I hope you didn't try to open up the ends of the runners where they flow into the engine. The slight mismatch is to help with reversion.

The carbs are interesting. Lots of complicated mess on them stock. Be sure to read up on the accelerator pump mod and mechanical secondaries. Those two mods are well worth the effort!