Hey guys,

Recently joined and have been trying to search and read rather than post up new threads but I need some help please. So I am putting a 13B-REW series 7 motor into my MX5, and yes while the fabrication part is consuming I can handle that, my questions are:

I plan on using the stock ignition module from the MX5 so I can run the stock ECU and have the stock tacho working, how do I wire the ignitors to work on the leading and trailing principal?

I will be removing the OMP after reading countless threads about premix, can I just leave the OMP unplugged since the MX5 ECU wont know any better and will that stop the OMP pushing oil through the injectors or do I need to remove the whole system to stop the OMP from functioning?

Thank you and sorry for a really lousy first post.
Ash

 

You can't use the stock Miata ignition. You also can't run the stock ECU.

The 13B uses a staged injection system. I also doubt it has the same triggers as a Miata, and there won't be any way to control the trailing.

I'd suggest a full standalone. The Haltech P1000 is a great ECU and there is plenty of support out there for it. You can likely drive the stock tach with a spare output.

If you are removing the metering oil pump, you need to install a blockoff plate in place of the the pump. Then replace the oil injectors with a bolt.

 

Thank you Aaron, I have spoken to a person here in New Zealand that has done the swap into his MX5 using the stock ECU just not sure how he went about controlling ignition. Could the leading and trailing not be set up using the ignition wires from the stock ignitor when it fires each cylinder?

Also thank you for the OMP advice, I will install a block off plate and remove the injectors just was not sure if I could unplug it and render it inactive.

Sorry I did not mention I am running a 750 Holley carb on the motor so no EFI.

 

He is likely running leadings only, since the leadings fire like a 4 cylinder and can be fired wastespark. How he is triggering the ECU, I have no idea. The trailings are timed to fire at a specific number of degrees (this varies through the powerband) after the leadings...it's just just one then the other.

Honesty his car sounds like a horrendous hack job.

Why the carburetor?

You can swap an earlier front cover onto the engine and run a 12A or GSL-SE dizzy so at least you'd have full leading and trailing. No boost retard of course.

 

Thank you for the reply Aaron. I am hoping it wont be a hack job since I will have everything done properly hence the millions of questions. So the 13B I bought has a carbie on it so I am using that for now and will go EFI later on, no turbo so it will stay NA.

The 13B is running a crank angle sensor ignition system. So after reading I can probably run the leading plugs just fine off the CAS but the trailings are where I get stuck, I need the ECU to control the trailing correct? Or can the CAS control the trailing as well?

I do have the RX7 ECU and loom as well but want to use the stock MX5 ECU to control my AC and other functions.

 

Spoke to the guy that sold me the motor, He suggested using the RX7 ECU he is supplying to control the firing and alternator and then leaving the MX5 ECU intact to run AC and all other functions. What are your thoughts?

 

So it isn't a 13b REW after-all. What are you gaining in the swap then?

 

How would it not be a 13B-REW if it came out of a series 7 body with matching vin plate? I am assuming he put the carbie on out of choice but yes its carbed and the manifold looks modified to fit so to me it seems the carb is in place of the standard EFI. Or did I miss something where a carb in place of EFI means its not a REW? Im not sure whats the big difference since I am just trying to figure out the ignition side of things, sorry but I have not really looked into rotaries as much as I wanted too initially so I am learning now.

I am hoping to gain knowledge and a bit of fun out of the swap, nothing more. I have my Supra for power.

 

It's not EFI and not turbo-charged. It might have come out of a S7, but after removing the turbos and sticking a carb on it, other than some design changes to the irons and housings over the years, and marginally larger displayment, it's not distinct from early 1980's 12a in that form....and IMO no longer a REW. That's why I asked what you hoped to gain from the swap... and the Miata's engine. I'm not intimately familiar with that 4 cyl. but always heard good things about it. You're looking at tons of work and at least some money and jacking with dual ECUs for the swap and not seeing any purpose to it. Why did your friend do it?

 

The more I think about this, I'm reminded that just because something can be done, doesn't mean it should be done.

 

Ah right that makes sense already, would there be any way of telling this is a REW engine or not? As for purpose its the same as why there are RX7's running around with 2JZ or RB26 swaps. The rotary would be fine in an RX7 and create good power for the application needed but there are just some people that like a challenge/to be different. Im doing the swap for fun and in the process learning what I need to know about the 13B, I see a purpose in the sense I get something positive out of it but to you not doing the work nor needing to learn anything about a 13B it would seem pointless.

I am not sure why my friend did the swap nor why a handful of other owners did the swap on their MX5 but I am sure its generally for the same reason.

I am sorry but I just really need to get my ignition and wiring sorted if you really dont see a point in the swap please maybe PM me or ignore my questions please.

 

In the New Member section I just try to help people. Sometimes that includes sharing an opinion they don't like. And in your case, asking a question you don't have an answer for to support that opinion. But your right.....in the end it's my opinon. So good luck and I'll ignore you from now on.

 

Thank you very much Sgtblue

 

ash I'm very intimate with the miata motor's LoL . and if the motor is not a REW- With the turbos .. THen you will gain NOTHING at all unless you add a turbo . and go back to FI Or port the motor , and then your stock tach on the miata only goes to 8k , LOL

its alot of work for such minor gains . Also maybe that friendo f yours ment he's running the same stock rx7 ECU .

just seems like alot of work for no gains at all . I'd suggest you do what arron said , Get a after market EMS , then then run the ignition independantly from the Miata's ECU , you will also have to figure out how to work the compressor wire the compressor to tie up with the Miata's harness

also which miata motor are we talking about?

 

Thank you TEM120. I am currently using the stock 1.6L with a few modifications however the 13B swap is just purely for fun. Its a lot of work I understand but I am honestly looking for no gains in terms of power, more so just to enjoy driving it to work and around the track.

The friend of mine is running the stock MX5 ECU but where I think he was lucky was that his 13B came with a 12A front cover/distributor set up so the ECU didnt have to deal with any ignition issues. I have a 13B with the standard CAS set up. I am looking in to a Megasquirt just waiting to hear back from the seller, but I honestly think the RX7 ECU controlling spark should work just fine seeing as it will be getting power and CAS signal nothing else so there wont be any issues?

Thats what I think but everyone on here will know more about it than me so if something doesnt make sense please tell me. For now I would like to just get it running and thinking of using stock ECU's. Also what compressor are we talking about? The AC? The wiring diagram on the MX5 1990 suggests the AC is run of main relay and fuses on the engine side, ECU has no input

 

This is what I am looking at

13B Turbo Rotary Programmable Engine Management | Trade Me

 

Since you are looking at a Megasquirt, read this first:

How To Megasquirt Your 2nd Gen RX-7

Honestly, if this is your first EMS install, I wouldn't say go MegaSquirt. A Haltech PS1000 is a great choice and there is a lot of support. Just that the learning curve of the 'Squirt is pretty high. Plus there aren't too many people running REWs on the 'Squirt. Not that it would be any more difficult than a 2nd gen engine or any other rotary really.

The RX-7 ECU needs a lot of inputs to control spark properly. All the sensors and the AFM (have fun integrating that with the carb ). A front cover swap and then a dizzy would be the "best" way.

Are you not running the REW turbo? It's going to be fairly anemic in that case, making about 150HP at the most unless it's been opened up and ported, then built with high compression rotors. Carburetors and turbo rotary don't mix.

 

Thank you for the link Aaron I have read it. I will be wiring the ECU up and will be given a base map to start/run the car. Then I am taking it down to the tuners to get it set up properly. As far as I know the motor was a apart and rebuilt while getting a street port so I am unsure on the lower compression rotors being swapped out but I can only hope. If they were not thats fine I can always do that at a later stage once its running properly.

I think the Megasquirt should be able to control spark just fine if its got all the variables. I can only imagine whats needed but I will have whatever the ECU needs connected so I am hoping its a fairly simple process.

 

No problem with MegaSquirt controlling spark, spark and fuel, or just fuel.

 

Once again thank you very much Aaron. I will be using the Megasquirt to run the low pressure fuel pump in tank, control spark as well as getting an inbuilt stock tacho output so I can run my stock tachometer. There is going to be 2x general out put relays off the ECU, one is controlling the cooling fans via water temperature sensor and the other might be a water spray output to keep things cold during track days.

The 13B-REW as far as I have seen has a oil pressure sensor so I am hoping I can keep that and run my MX5 wire to the sensor to keep the in cluster oil pressure gauge.

I am on the fence about the OMP delete? What are your thoughts now I have pretty much everything buttoned down. I will run premix thats for sure, so just disconnect the OMP and leave the lines connected just plug them or use a really short bolt to plug the feeds?

 

premixing my street ported engine which will see daily driving use I worked out at 430Ml to 45L full tank. Does that seem too low or should I increase the amount of premix? I will be using the standard OMP with semi synthetic oil. I was looking at these options:

Castrol Power 1 TTS Motorcycle Oil - 1 Litre - Supercheap Auto New Zealand

Valvoline Racing 2 Stroke Oil - 1 Litre - Supercheap Auto New Zealand

Silkolene Super 2 Motorcycle Injector Oil - 1 Litre - Supercheap Auto New Zealand

 

That's about the ratio you'd want....150:1 for a daily driver if your are NOT using the metering oil pump.

There's no reason to premix if using the metering oil pump.

Really, any two stroke fuel injection oil will do the job. Buy whatever is on sale.

Now...you've gone through all the trouble to wire up the MegaSquirt to run the ignition, so why not connect up the 4 additional wires so it can fire the injectors as well? It seems backwards to run the terrible carb when you're 90% of the way to EFI after the MegaSquirt install.

 

Awesome thanks Aaron. I will run the premix just to be on the safe side should the OMP malfunction or stop working. I will tune for EFI later down the line, right now its getting everything running and working together happily. I have asked the person building the ECU to leave the injector wiring there and have already asked for a second map to throw on once I get the EFI components together.

 

Metering oil pumps don't fail. There's no reason to worry about it. Assuming you are using the front cover from an earlier car the metering oil pump will be totally mechanical. Only the electronic pumps used in later cars have a tendency to fail, and in that case, it's normally just the position sensor.

You won't need alternative maps for EFI or just spark control on the MegaSquirt. If you don't want it running the injectors, just don't connect the injector wires and don't bother tuning fuel.

 

Thank you Aaron I am using the S7 front cover from then13B so the OMP is electronic. So you suggest just running the standard OMP and not worry about premix?

I will run the carbie for now and leave the EFI wiring tucked away but will wire it in later when I go EFI.