ecu mystery
 

I am building my own budget concept car powered by a rotary engine. It's based on a street legal Rail Buggy with a body made of cloth. It was originally powered by a VW motor. But. I blew that one up. (I always wanted to do that). The original design intent was to swap up to a rotary motor. So, it's time!!!! See the car at my website www.bellemachina.com/id26.html

So, I found a 1989 motor on CL locally and ordered the Kennedy adapter kit that had been taunting me from the back of magazines for years. Two months later, the motor is mounted with all cooling, oil, and fuel systems plumbed. The only thing left is wiring the Wankel's ECU. The ECU came with the engine along with a truncated and attached harness. I even have the plugs for the ECU.

This is where the confusion starts and our mystery begins. My ECU is marked as "N351" and has only two plugs. Those two plugs contain 16 and 20 pins. All of the documentation from Haynes, the FSM and the typical sources (foxed, rotary restoration, luvmyrx7, rx7club) refer only to 3 plug ECU's. The specified plugs have different numbers of pins and a completely different colors for the incoming wires.

So, does anyone out there have a pin out diagram for this odd box?

Can you post a picture of it?

Because this is an N351 ECU, and it accepts three plugs...

http://www.rhinehartsautoparts.com/r...s/pics-009.jpg

the mystery box
 

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That's not an ECU. It looks like a cruise control unit.

ditto
you want the ECU as pictured in DWB87's pic.

Can anyone post a pic of a similar cruise control unit?

Are the cruise control and ECU similar in looks?
The box I have has far too many wires for simple cruise control. Granted, I'm not the expert on these elements. But the numbers for this ECU are located as reference all over this site.
Do the cruise control and ECU have matching part numbers b/c they come in a set?

Electronics are grouped by the 4-character part number prefixes. Different years; different prefixes. That is 100% not an ECU. Whoever you bought it from ripped you off.

You can look for yourself in the parts fiche: http://www.rotaryheads.com/PDF/2nd_g...20BODY%20b.pdf

The "ecu"that you have is about 3x3inches.
The Engine ECU is about 5x7 inches.so it is BIGGER.
The N numbers are the specific year numbers that the car uses..(like N326 is for 1986...N351 is for S5 1989-91)).
The Cruise does not need to be hooked up anyways,It is on a harness that is separate than the harness that you need to run the engine.
Have you considered putting an aftermarket ECU in?..like a Haltech?

Thanks! I found my box in the docs. Page 43 on my PDF reader. The part number matches mine N351 18 9E1B. It's called a PWT module mounted on the kick panel on the passenger side. 4" x 6.5" x 1.25"Without the actual car, Im working from these images only. So the help is greatly appreciated!! Anybody know what a PWT module is? I searched the term here but got no results (search is down) Maybe I can sell it off on eBay.

If I have to replace the unit, then I have to replace the unit. But If it comes down to that, a simple carburation and coil system may suffice to easily increase the power. As much fun as fuel injection is to play with, it may be too complex for this simple craft. See the car in my other thread under "body bag". I never expected this to be plug n play, but having the correct components makes things go remarkably easier. The intel here helps! Thanks to all

the actual install
 

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very nice toy

The problem is that if you carburete it, you'll have an engine that only makes decent power at WOT and high RPM. The 6 port engines have massive port area that can really only be used up top, hence the aux port actuators and two stage intake manifold on the S5.

Plus carburetors suck.

dv8 Racer I would encourage you to stick with the injection .. I have gone the carb and single fire ignition route . With help from Aaron and a few of the members I managed to get every thing changed over but If I had it to do over I would stick with the fuel injection and electronic ignition . Although I did manage to over come most of the problems mentioned , in my opinion you will be much better off spending some time learning the electronic route as misterstyx mentioned there are different ways to go about it . I can't speak for Aaron Cake but I bet he would help guide you along a bit just to keep you from using a carb .:lol: your in good hands here good luck .. Gerald m.:)

An archaic microtech can be found used for a cheap price and tuned properly will yield more power. I would think a standalone would fit this project better anyway

The donor engine and ECU (maybe) cost me $500. A used microtech cost more than that and used electronics have no warranty. A new controller costs 1k (+). The economics of the little rotary may have just been exceeded. A variety of running engines can easily be acquired for far less than this "solution". No wonder they don't make them anymore.
I need a running engine, not another hobby. I'm a designer, not a mechanic nor rx7 specialist. The legendary simplicity of the rotary engine was the appeal. The zealotry required to make this one run has already blown the time budget. Tripling the financial investment may produce only nice used parts for the classified section of this forum.

Stop making things so complicated, and just make a WTB ad in the classifieds for an N351 ECU. It won't cost you more than $20-50.

Yeah, we designers make everything more difficult... the first time. That's how tomorrow gets made easy for everybody else. Thanks for the reminder.

I think everything has been covered, but I'm just replying because this question was also PM'd to me.

I agree. A Microtech is properly described as archaic and really, for the $500, you could have a far more capable Megasquirt. Or just buy a used RX-7 ECU because they are cheap. What you have there is a cruise module or an automatic transmission controller. With so few auto RX-7s I can't say I've ever seen one in person, but going back on my memory, that's what it is. The cruise module has a little slanted area at the top. Hell, it may even be the auto suspension computer.

Why would you ever buy a new ECU when you can buy them used all day for $20?

That's kind of an odd statement to make. I don't see how the fact that you bought the wrong part, and then didn't believe it was the wrong part, and then only considered buying the correct part new from the dealer has any real relation to the engine? Get a Toyota 4 cylinder, then price an ECU from the dealer and I'm sure you'd find them at a similar cost. Used ECUs and other rotary parts are very cheap. There were a lot of them manufactured.

You ended up with the wrong part. How is that at all related to "zealotry" required to make the engine run? It runs perfectly well on the factory wiring when you use a factory ECU. There's really no rocket science to it, and it's like any other engine with regards to the EFI system.

And hell, if you really wanted to go carburetor, used Weber manifolds are cheap, then use the dizzy from an '81+ RX-7, and Bob's your uncle.

Good reply. It gives good arguments to include in my own head.

ECU heritage

1. The ECU I have matches every possible description (size, shape, part number, and original mounting location). The only difference is the number of plugs.
2. Mazda, according to this site, made many versions of this part. The heavily reproduced FSM on the web shows only one version of an ECU with 3 plugs.
3. No one knows what my little silver box is. (If anyone knows, post a pic!)
4. Cruise controls and 1989 suspensions systems didn't have/ need 24 wires to work. (I used to install all kinds of electronics in cars for a living then)
5. If the ECU I have is indeed some other electronic gimmickry instead. Then cool. I'll have to buy one. No problem. I make mistakes all the time. Tis might just be another. But here's the rub... If I don't know the ECU, then I don't know the wiring harness either. That means a full re-wire of the engine before adding a matching Replacement ECU.
6. But, if my ECU can be authenticated, then I can provide this new information to all the folks encountering one of these strange little variations of production. (this stuff happens frequently. I make Product lifecycle management tools for a living. It tracks these changes through the production of new product)


Zealotry
1. No offense was implied or expressed.
2. I'm a zealot for things I believe in. I listen to other zealots. They're sometimes wise, and always more interesting.
3. Zealotry includes the undying love for a dead idea, car, or any other product. (that's why religion stole the word)
4. Fans buy t-shirts. Zealots build websites, fill empty spaces with parts, and write books filled with ideas and stories about their love.
5. Zealotry can cause blindness and tunnel vision. So, I'm adjusting my scope.

Replacement.
1. There are a variety of less expensive, more modern, and more efficient used engines available on the market.
2. Plug n play fuel injection has been vastly improved since 1989. All the electronic components and architecture of cars have Improved exponentially thus allowing for ore advanced maps and robust service. That's why most folks upgrade, right?
3. I wish they still made these engines.
4. This is my first rotary engine. I'd like to make it run and keep it.
5. As cool as this engine swap is.... There is YouTube video of a fz1000 motorcycle engine on the back of a VW. Junkyards are filled with shattered sportbikes with useless, new engines. Newbies total these things all the time leaving low mileage, high quality scrap.

Another clue, or distraction
 

One more thing about this 2 plugged mystery. Using the referenced manuals, I found nothing that had the same plug configuration or wire color set that matched the truncated plugs that fit in my "ECU". I was attempting to identify this as an a/t controller or suspension system device.

The engine was not from an automatic. I removed the clutch and had to add the counterweight for the conversion.

Did the rx7 have an electronically controlled suspension system in 1989? Just asking. Was it pneumatic, or electrically actuated?

It could be the automatic trans computer, and the car was a swap to a manual. Very possible.

I found you one for sale! $30 here https://www.rx7club.com/showthread.p...highlight=n351

It's the EC-AT, automatic transmission controller. Two plugs, 16 and 20 pins. 8 slots are unused.

Now stop calling it an ECU.

Search-able S5 FSM, wiring & parts fiche: https://docs.google.com/leaf?id=0B-v...notVXhlakY0SG8

https://www.rx7club.com/attachment.p...1&d=1336247697

Looks like the mystery is solved; automatic transmission controller. It's just likely that no one recognized it because very few automatics were sold, and even less of them are in enthusiasts hands (for good reason). Mazda was a bit annoying by sticking the version number on all the parts. That is, the ECU says N351, as does the AFM, as do some of the other modules. It can be confusing.

Honestly though, all the strange little variations in production have been accounted for. There is nothing left to discover regarding which ECUs were used in which cars, and the variations in wiring. It's all well documented since these cars have been around since 1986.


Probably, yep. However for displacement to power output, it's still hard to beat the rotary. In NA form, it's hard for them to compete. However in turbo form, that is where they shine. I guess it mainly depends on how much power you want. There are plenty of 150HP 1.6L piston engines around (Honda). If you are looking for 300+ HP in a compact and light package, the turbo rotary is hard to beat.

The only thing about these high revving motorcycle engines seems to be that they are far less reliable than the rotary. At least, that's the impression I get from my bike friends.

Anyway, now that you can find an ECU, it's fairly simple to go through the harness and simplify it to just run the engine with nothing but a connection to 12V. Note that you'll need to add the missing parts of the harness which control the coils and read the signals from the CAS. These would have been part of the front body harness and engine harness, which I'm assuming you don't have.