dan_boy

Hi,

I've been looking over past posts about which engine is better and which apex seals to use.

From what I can gather, a 13B engine with 12A end irons is the best engine and apex seal type depends on the application. I want to N/A the engine and fit a carb, for road use mainly.

I have an engine from a FD (I assume it is a 13B) which over heated, but there is a non turbo FC for sale near me (this I believe is 13B also?) and this 84/85 FB http://cars.donedeal.ie/for-sale/vintagecars/1891397 which am I right in saying has a 12A engine?

From a previous post, it was stated that anything '85 or older and '86 and newer bolts together without any problems but can't be mixed. According to this, the 13B engine I have and the 84/85 12A engine I can buy, won't be able to mate together to make a 4 port 13B without machining a new coolant seal groove into the housing?

Can anyone confirm for me that I am right in what I am saying above?

What I want is a good driveable rotary engine, possible with 200+ brake, cost depending, so would I be better to just stick with a 6 port 13B engine and bridge port it, or try to get a 4 port engine and work with that?

Also finally, for normally aspirated, road use, would ceramic seals be a bit excessive or would regular steel seals be up to the job?

Any help you can give me lads would be greatly appreciated.

Cheers
Dan

diabolical1

iTrader: (3)

Dan Boy ~

before i start, i just want to note that your research is commendable. keep it up. it is key in learning about these cars.

anyway, you are correct. your REW (FD engine) will not be readily compatible with the engine from a Gen I. aside from that, it's already a 4 port, so there would nothing to convert.

since you don't already have a chassis to put your engine in, i would say weigh your options carefully. however, my only concern is that the engine you have was overheated and it doesn't sound like you have it apart yet to see if it's rebuildable. i would say since whatever car you end up getting would eventually be centered around this engine, you should probably find out if it's any good.

as for whether or not you should use ceramics, i think they would be excellent in an N/A engine. however, at your level (no offense meant) i would start off using basic parts. ceramics would necessitate new housings (or at least housings that are perfectly smooth/flat) and since i don't get the feeling that you've done any of this before, i would say just go with OEM (or similar) seals/parts and wait unitl you have more experience.

dan_boy

So the turbo engine from the FD I have is 4 port already? I thought all 13B engines were 6 port or is it just non-turbo 13B's?

Ya the engine I have overheated and was then limped several miles home so I am really expecting the worse when I do strip it open.

Don't worry, no offense taken. I could give the engine to a builder here in Ireland but I don't like cheque book cars and the only way to learn is by doing so.

Cheers
Dan

FC_fan

iTrader: (2)

yes, 13b na engines are 6 port. 13b turbo engines are 4 port.

if 200hp is your goal, ceramic seals (apex seals anyway) or not needed at all unless you want to spend A LOT more. oem mazda seals have been used in 400hp cars in all forms of racing and that is double what you will be running. I think that ceramic seals might be harsher on the housings too and wear them more. they are for race cars basically, high hp engines that get rebuilt regularly.

yes, that car is an FB and has a 12a stock. they have a model of FB called the gsl-se which basically has the same 13b na that is in an FC (86-88 models). so I think it would be easier just to get a 6 port 13b na and put it in. the only thing you might have to do is put a 12a front cover on it (not sure if you have to). This idea is for your power numbers you want, FC 13b's are fuel injected though. for simplicity, you can use a stock 12a which is carbed but it will be hard to reach 200hp na with that platform. these are just my opinions on the matter though, and I'm not too sure on the specifics of the 1st gen cars.

You may want to ask in the 1st generation (FB) section here as well, you will probably find lots more help if that is the car the engine will go in.

diabolical1

iTrader: (3)

i neglected to mention a few things before:
1. if you're going to use your REW, you'll have to figure out mounting in either the FB or FC. it can be simple or quite tedious, depending on which chassis and how you go about it.
2. since you're going with a carburetor, you've pretty much taken away one of the major differences between the FB and FC. so aesthetics aside, do you prefer live axle or an independent rear? there is aftermarket support for both suspensions.
i fully support doing it yourself. i, personally, think that that's where 95% of the fun is. however, the only true judge of your abilities is you. there is no shame in being practical or realistic.

FC_fan

iTrader: (2)

If you do find all the answers you need, and decided to rebuild it yourself, aaron cake (very knowledgable FC guy) just posted a very good video on putting the shortblock together of pretty much any 12a or 13b. its all pretty much the same as far as assembly. here's the link: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/video-13b-rotary-engine-rebuild-945517/

and this for checking parts: http://rebuildingrotaryengines.com/

that's some good, FREE info there. you can also buy rebuild dvds from atkins rotary or mazdatrix but the links I posted should tell you most all you need along with a haynes manual and the Factory Service Manual (FSM's are located in the 1st,2nd,3rd gen sections FAQ's)

fwiw, I've never rebuilt a rotary OR any other engine and I'm very confident I can do it myself on my turbo 13b which I will be doing when funds allow.

diabolical1

iTrader: (3)

simply not true.

snivley whiplash

iTrader: (4)

dan_boy,
I currently own a 1985 gs model with a 13b six port installed. I run a dellarto side draft with a racing beat intake and racing beat full exhaust system. the front engine mount is also a racing beat mount with hockey puck mounts. almost all engine swap parts can be purchased from them. my engine install looks great and performs well. the s4 is a great base engine to work from.
I do not know the brake numbers from my set up yet as I am still dialing it in. also, when going carb on a rotary, make sure you invest in a wide band o2 system to monitor air/fuel ratio as this is a great tool when tuning. there is also set up and tuning issue you will need to look at to get the hp numbers you want, mine is an innovate system with the data logger installed in the glove box and a digital display mounted on top of the steering collum.
when you get to the set up of the engine and ignition system, my suggestion is to run the stock 13b dizzy with no vacuum applied to the vacuum advance pods. The next step is VERY important to make good power. The max timing on the leading side should not exceed 27 degrees at 4000 rpm and the trailing side should not exceed 16 degrees at 4000 rpm. is this happens engine damage to the apex seals will result from predetonation.
hope this helps in your choice of engine and goals

Joe

dan_boy

Thanks for all the help lads.
fitting the engine is a different issue because I'm not fitting it to an rx but to this instead.


So am I right in thinking that I should just rebuild the 4 port 13b using regular apex seals and go from there?

I haven't thought anything about carbs yet but thats another days work but since the engine was turbo and I will be carbing it, what would I have to do regarding the dizzy and stuff? What are my options?

Cheers
Dan

FC_fan

iTrader: (2)

I don't know a lot on ceramic seals, only what I've read so I may be wrong there but iirc, ceramic seals are around $1k usd for a set aren't they? doesn't seem worth the price if oem seals would work fine as they are several hundreds cheaper.

Wait, I must be confused. I thought you were putting an engine into a 1st generation rx7 (aka SA/FB)? Or are you just getting that for engine parts then?

I don't know how a 4 port would be na. they are all stock turbo so maybe the power curve would be ****. in the 6 port engines, I know they run on 4 ports until around 3800rpms, at which point they open up the 5th/6th ports. those ports are activated by exhaust pressure in 86-88 s4 FC's, and electronically on 89-91 s5 FC's. I know some people wire their 5th/6th ports open sometimes (mostly due to them not operating correctly) so maybe a 4 port na would have a similar curve?

j9fd3s

iTrader: (3)

4 port is fine NA. all of the NA cars prior to the 84 GSL-SE (in the US*) are 4 port. mazda has tried different portings over the years. quickly, mazda found that making the 4 port engine with bigger ports added top end power, but low end (sub 2500rpm) power suffers. so in order to deliver a car with more HP and the same or better low rpm power, came up with the 6 port system. the 6 port engines run from 4 small ports at low speed/load, and then at high RPM/high load the aux ports open, delivering more power up top.

however in the real world, when we can uncork these things and want to go racing we find 2 things.
1. nobody cares about the torque under 2500rpms
2. you can't really port the 6 port engines very much, which is unlike the 4 ports.

so its a well trod path to run a ported 4 port. the FD engine actually would be the best core to start with, it has a lot of small updates which will support plenty of HP and rpms.

*different markets got different models, the 1st gen for example, you got a 2+2, with an NA 4 port 12A (which has bigger ports than the us spec!), and the big brake/wheels. for the US, we only got 2 seaters, the big brake/wheels were an option that came with a 13B

diabolical1

iTrader: (3)

the photo doesn't seem to work for me. all i got was a red X.

don't worry about apex seals so much, at least not now. just keep the rebuild basic - as simple as you can. OEM (or similar) is all you need. if your engine is not totally hosed from overheat, just rebuild it as is - although i'm not sure i'd trust the bearing even they spec out. don't worry about fancy seals or higher compression (you have 9.0:1), you can make good power with it as you learn and get experience under your belt. save the fancy stuff for the next go round.

for the carbs, you have a few options, perhaps not as many as older engines, but you can find something good.

for the ignition, the simplest thing i can think of is get an older front cover (and timing gear) so you can just put a distributor in there and call it good.

dan_boy

Thanks again for all the help lads.

So what I have decided is to stick with the 13B FD engine I have here and rebuild with oem seals. I have also found another cheap FD so I might buy that as it will give me the gearbox and any parts I need to fit to this car.



Just to confirm, is the compression ratio of the turbo engines I have as high as 9.0:1? Seems very high for a turbo car. Will I need new rotars to increase the ratio?

diabolical1

iTrader: (3)

nice. what kind of Opel is that?

as i said, if your engine turns out to be in rebuildable shape, just focus on doing a solid build and then tuning it. don't sweat stuff like compression and apex seals right now. you can make good power with the 9.0s.

dan_boy

It's a 1979 Opel Kadett C. It's actually in this condition at the moment.



Ya you are right in what you are saying and just get a running engine first, then worry about power figures down the line.

Thanks for the help but I'm sure I will be asking plenty more in the future.

Cheers
Dan