Hey guys, doing my best to absorb as much info as I can here. I thought I might throw out a question about rebuilding engines.

Rotary engines, to me, seem to be a bit more simple in their design than conventional piston engines, so how does the rebuilding process compare? Is the rotary any more difficult or easier to rebuild than a conventional engine?

Any thoughts welcome, thanks.

 

I think a rotary is extremely easy to rebuild vs a piston engine. The rotary has far less parts, which makes it less time consuming to clean and measure all the parts to see if they are in specs, and no special tools required like a piston ring expanding tool. You need the big 2 and 1/8th inch socket and impact gun to take off the flywheel nut, and the bolt holding the main pulley on, but other than that, a basic metric socket set will take apart the whole engine. I also like how the block comes apart into plates, instead of a solid V block or 4cyl block. Makes it easier to clean and each part is lighter and easier to handle instead of messing with a whole engine block.

Anyway, I think the rotary engine is easier to rebuild than a piston engine.

 

Well put, that all makes sense, thanks for the reply Project84. So there really are no special tools needed to reassemble a rotary? That does sound easier. What about machining work, do the rotary housings need to be "honed" or something similar?

Any more input would be very much appreciated.

 

nothing on the rotor housings...if they're bad, replace them.

the irons (front, rear, and intermediate housings) you can get lapped for good measure. i've done engines using lapped and non-lapped housings with virtually the same results, so i don't think it's the end of the world if you don't have it done...it's good for a bit higher compression numbers once it's broken in, though.

tools are the basic tools...
then:
flywheel nut socket 54mm or 2 1/8" works)
flywheel stopper (or a piece of angle iron with a couple holes drilled in it)
dial indicater (for setting end play)

then stuff like rtv, hylomar, assembly lube or oil, petroleum jelly, yaddi yaddi.

 

Wow, so really just a good set of basic sockets and a dial indicator will get the job done? I had no idea it was that much simpler.

Lol, petroleum jelly!?

Thanks guys, I am getting more eager to get my hands on an FC now.

 

superglue to hold the apex seals together

 

*writing list down*

Right, so, superglue, petroleum jelly, box of Ho-Ho's in case I get hungry....

 

Beer
EDIT:

 

the rotary engine is a breeze. just take your time if it's your first rebuild. Remember, the people who brag about taking their engine out and having it half apart in 3 hours, are experienced. i'm 16 and i'm just now finishing up my rebuild, and man does it feel smooth! I can turn the eccentric shaft and I can't even feel any grit or anything holding. it's butter! and i love hearing the air shoot out of the ports when the rotors move around. the real test will be when it's in the car, but it looks like it's a smooth road ahead of me.

Get a Haynes manual, and search in the forum for the FSM.

also, be sure when you disassemble your engine, put your rotors in a good decarbonizing bath. I like to first use some purple power cleaner, scrub, then let them sit in a bucket of ATF overnight. the next morning, carbon has fallen off and is now a sludge on the bottom.

hmm... for the rebuild kit, i suggest rotaryaviation.com's kit.

-Chris

EDIT:
rotaryaviation.com's apex seals don't need superglue to hold them together for assembly, and i think that goes for some others if not all aftermarket seals.

 

Wow, I actually thought that originally was a joke, I didn't know the superglue thing was serious! Hmm, learn something new...

 

 

There was once a complete list of parts needed for rebuild on the "team FC3S" site. Not sure it's still there.

Main reason it's so "easy" is you can't machine the rotor housings (other than porting). If they're scratched you buy new ones. The rotors can be machined (apex grooves if they are worn too much - and are usually then taken to 3 mm seal size) but it better be done by a very good shop. They are kind of fussy. You loose the hardened surfaces when this is done.

Usually to get an engine that lasts a few years you buy new housings and rotors. I believe these parts (housings) are back-ordered - Mazda foundry is tied up making renesis parts because the RX-8 is selling so well.

 

I can build a rotary in about the same time it takes to build a set of cylinder heads.

The higher prices for parts for the rotary are greatly offset by the lack of machining costs, which can be a *huge* factor depending on what boinger you're building.

I priced out over $1000 just to do a cam swap on one of my V8s, and that was probably heavily undershooting the labor prices (to have the rocker stands milled down for adjustable rockers, and the valve guides milled down for low profile seals for retainer clearance, and possibly have the pistons flycut). For rotaries, that is obviously a non-issue.

 

I can live with that, I definitely would prefer being more hands on if I build a rotary of my own, less work at the machinist means I'm doing more. Which sounds good to me.

Just a thought, are there any aftermarket manufactured rotors/housings? Is it possible to upgrade in a similar fashion to piston/rod engines using aftermarket internals? Just thinking you could upgrade, and sidestep any backorder delays through Mazda.

BTW, thanks to everyone contributing here, I'm getting alot of helpful info so far.

 

there are a few options out there for rotors and eccentric shafts - aside from Mazda, but those are usually parts with a purpose in mind. most are not worth the extra cost for the ordinray joe, you know? at least, that's my opinion.

the stock Mazda ware will take anything that that other stuff can take. what you want to do is figure out what you want from your engine and modify it accordingly during the buildup. for example, the approach that you'd use to build up a bridgey may be markedly different from building a streetport for forced induction.

 

I was not aware that anyone other than Mazda was manufacturing rotors.

I know you can get *modified* rotors, for light weight or lower compression or both, but those start out as Mazda-made parts.

RB used to sell aluminum side housings. Pretty much anything you get as far as engine parts will have come from Mazda, either directly or indirectly. (With exception of some hard seals and the soft seals)

 

Interesting stuff.

As far as my plans go, that is still undecided. I have to actually get a car first. That is of course, why I am doing much preliminary research.

Thanks for all the help!

 

Could someone please explain a bit more about different setups commonly used, and the main differences? I'm looking for something mostly stock that I can tune for more power at the track on weekends but still get decent mileage for city driving as well as long life of components. I'm an apprentice auto technician (mechanic) so I know quite a bit about piston engines and the basics of rotaries, and I've rebuilt several I4's and a V6 but have never even seen a rotary before...
Also could someone give me some guesstimate hp/torque numbers for 13B variants both NA and Turbo?
One last thing I was wondering, are the NA and Turbo basically the same except for the manifolds, or are the internals of the turbo beefed up for the higher psi? I'm thinking of buying a NA and when I can afford to buy the turbos and manifolds swap them onto the NA housing, would that work?
Any help is much appreciated

 

n/a is a 6-port setup
FI uses a 4 port

IIRC 13b N/a ~130-160 hp ~130 tq
TII is 180-200hp
13b-rew is ~250 hp
but as fa as the internals, s6 plate are stronger, but other than that i dont know of much difference, stock rotors and e-shaft can take ALOT of power wheteher from a n/a or FI

 

go with a mild-to-slightly aggressive streetport. aside from that, a few relaibility mods here and there will get you what you say you want.

- manifolds are different.
- rotors are different compression.

yes, you can turbocharge an N/A rotary, that's the easy part. your work and most of your cost will come from tuning it if you intend to run higher boost levels.

peejay~
i think you're absolutely right on this. i was just referring to customized rotors and eccentric shafts as being the "options" i alluded to - i said it simply because you wouldn't be getting these from Mazda. these are parts that companies/individuals buy as Mazda parts and then do their own thing with them. i guess i should have been clearer. i, personally, do not know of anyplace that actually makes rotors, housings and e-shafts either.

 

here's a good place to start: Engine Building Thread
there are some others, some may even be better, but i like this one and it's usually the first that i would refer someone to.

 

Nope.

'74-78 were 4-port carbureted.

'84-91 n/a were 6-port fuel injected.

Turbos were 4-port fuel injected.

 

yeah yeah i forgot about the older 13b's
4-port love

 

allforjesus06, you are just 16 and doing a rebuild? you are the greatest!!!

 

Im 17 and I just finished my rebuild + large streetport. 1k miles on it so far and its running strong as hell. I love my rotary engine.