Rotary Miata
 

I've decided to swap the 4 cyl in my miata for a rotary. I've narrowed my choices down to the 13b-rew and the renesis. I'd prefer the renesis for the weight savings. My main concern is management. I'm aware the ems options are limited for the rx-8 because of all the other stuff the stock computer is in charge of. What systems are different between the 2 engines? The miata is pretty straight forward. The engine computer doesn't have much to do with the rest of the car. Would a computer that works for the rx-7 be capable of managing the renesis?

Also, the majority of discussions involving engine failure seem to share the idea that it's a matter of "when" rather than "if" Could I attribute this to a love of rotaries that runs so deep that people drive them until there's nothing left of the engine? Or am I to assume the engine might not last as long as some others? How many miles should I expect out of it?

I'll leave the question about the engine management to somebody more knowledgeable, but I'm guessing it might be easier to deal with a 13B-RE or REW than trying to wire in everything the renesis needs.

All engines are when rather than if. Rotaries in general can last a long time, and I believe there are a fair number of RX8's with over 100k without any issues and still going strong. Run the correct oil for your climate, change the oil religiously, and make sure your cooling system is up to snuff for your climate and you probably won't have any issues. Doing the engine cleaning procedure using seafoam (or whatever else) every once in a while is a good idea too.

There is some debate on the renesis if there is adequate oiling of the rotor housings, and there are some pictures posted on this site of engines that have been torn down making it look as though the OMP coverage (rather than the quantity of oil injected) of the 2 ports isn't adequate. Fueling that idea is the fact that Mazda added a 3rd port on the 09 model... because of this, many people recommend premixing a small amount of 2 cycle oil in the gas to help with lubrication.

Anyway, it's an interesting project, and I'd like to hear how it turns out if you decide to go forward with it :)

Oh well 100k is fine, by then I'll be ogling some production version of the 16X. I'm just not used to seeing so much discussion about engine failure and lubrication in an automotive forum. This will be my first rotary. I've heard all kinds of horror stories, and people that swear by them too.

I'll post updates as I go but the project won't start for a while.

here's the car I'll be working on. http://www.cardomain.com/ride/3115605

Remember, you have emissions systems you have to deal with in a post 1996 car. I wouldn't use a Renesis for a swap due to the engine management issues. I would think a 13b-RE would be the better swap if you want the rotary engine.

I guess what I'm trying to find out is if there's anything other than fuel and ignition I'm going to have to concern myself with.

Is this OMP controlled electronicly?

I heard something about a variable intake similar to the VICS on some Miatae. Can anyone verify this?

If you wanted to swap a Renesis into a Miata, you would be better off getting an entire wrecked car and using everything stock to put the engine in that is possible. With the complete wiring harness and ECU, there are only changes to the Miata you need to make so that it will fit.

On the Renesis, yes. By the PCM. Earlier 13B's are mechanical.
You would have an easier time putting a Renesis in a NC. All the wheel sensors are already there. The question I have is how the PCM interfaces with other systems like the dashboard.
For questions about the PCM, PM "Hymee" or "MazdaManiac". They are the ones that probably the most experience there.

Has been done
 

Several years ago I helped put a 89 turbo II in a Miata. I did all the electrical. This was a complete swap and smog legal including the cat, trans, rear end and brakes. All said and done it cost somewhere around 30K. The power to weight ratio was nuts. It was in Car and Driver I think.

By the way
 

A Renesis would be MUCH harder electronically, but maybe easier mechanically. (no sub frame mods to make room for the turbo)

http://forum.miata.net/vb/showthread...=285154&page=1

http://videos.streetfire.net/video/M...rew_163399.htm

http://compositeenvisions.com/index....ored_show_cars

seen it done in na's but no nb's yet.....could be a monster though

Hey Guys, we have been performing this swap for several years and sell a kit to bolt in the MUCH stronger Turbo RX-7 running gear as well. We can also help with the engine management side of things by providing a plug and play ECU, harness and mapping to suit your needs.

Here is a link to the kit!

http://www.mazsport.net/store/index....t_detail&p=316

Thanks, Scott

The PCM doesn't interface with any other systems. I have aftermarket gauges that take their signal directly from the sensors. There's really nothing else in the car.

I had pretty much expected to have to use the DIY computer from megasquirt.

Forgive my ignorance, but why would I need wheel sensors to make the engine run?

So far I have fuel, spark, and OMP. I've seen some kind of valve on the intake manifold too, I can't tell if this will need some kind of control by a computer but if so it shouldn't be a problem. Are there any other engine bits that would need a signal from the computer?

As for the stronger rx-7 guts, my trans, diff, and axles are plenty tough enough for the renesis. I have the 6 speed manual which IIRC is the same one in the rx-8. The miata guts should be fine up to about 350hp.

The APV motor is controlled by the 8's PCM I believe. This opens the extra intake ports at specific RPMS (3750, and 6250 I think). I'm not sure what controls the VDI valve... that's possibly also the PCM.

you could try to contact mazmart, they do rotary swaps into miatas

Of those of you who have owned both engines, which did you like better?

After some discussion with a few shops I think I've decided on the 13B-TT from a Cosmo. I have the beginnings of a plan for the start of a project! WEWT! Phase 1 will involve resource gathering. First I must find a source of green papery things that can be exchanged for goods and services. Then I need to use the green papery things to purchase bits and pieces to begin the project with. After some careful thought I think I will join the Army to provide me with the green papery things I need. I will post updates after I complete AIT.

Good choice.

The 13B-REW from a Cosmo has huge ports as standard. Will you be removing the REW part (rotary engine double-turbo) & going "Atmo".? If so then the 13B-MSP engine would give more bang for buck.....

Get a Haltech or better aftermarket ECU than can control actuators & the OMP

REgards

I will be keeping the factory turbos at least at first. Does anyone know if the Cosmo version came with the Efini turbos? Should I be looking for a 99+ engine from a 7 or what? I've been doing some research but results conflict. I'm not very trusting of most of the JDM engine importer sites I've found because the "specs" don't seem correct for the engines I've looked at and I've seen the same engine photo shared between more than just a couple different companies. If anyone could point me to a good source for rotary engine history and maybe a way to identify them that would be awsome. I'd like to be able to know exactly what I'm looking for and be able to tell if I'm getting ripped off or not before I spend any money.

Mazda did 2 types of 13B-REW..

JC Cosmo - 90-95
FD RX-7 - 92-02

The JC 13B-REW has larger ports & better low end torque. The FD 13B-REW have higher flowing turbo's (20% extra) for more top end.

The term "Efini" was the sales channel Mazda used to sell the JDM RX-7 Series-6 (92-95) + Series-7 (96-98). The Series-8 version (99-02) was sold as a "Mazda" in Japan.

To answer your question. The FD turbo's wont bolt up to the JC engine. Between 1990 (JC) & 1992 (FD) Mazda made a lot of changes.

REgards

So what I'm looking for then is the engine from the JC Cosmo. What should I look for to identify this engine? I plan to find an importer, drive to their shop and make my purchase in person so as to avoid any problems. Thanks for the info so far you've been very helpful.