RIWWP

iTrader: (2)

I am working on the plans and materials for swapping a Renesis (NA) into a NB series Miata (1999 or 2000, I have a 2000 located that I am about to buy if everything checks out). Likely the work won't start for another 10 months or so, but I am working on the research and investigation into what I will need early, rather than stepping into it without a plan.

This is just a thread to discuss my ECU options for the engine swap (including wiring harness). If we can keep to that topic, it would be great. Thanks.


So what input and thought to people have on what ECU options I have, and the pros and cons of each. As I see it right now, my options are:

- Complete stand-alone ECU (Motec or other)
- An ECU piggyback onto the existing Miata ECU that can take the Renesis sensor data
- An ECU from an RX-8

The ECU from an RX-8 has the advantage of probably being fairly cheap and easy to obtain from a wrecked 8 (yes?), and it is a known Renesis ECU on the boards here for Access Port tuning, even though it's in a different chassis.

The stand alone and piggy back have the disadvantage of being more expensive, and possibly more difficult to get assistance tuning from the forum here, although it might be easier to find a shop able to tune it. Though I don't know that I would go that route. Only Synaptic up here seems to have experience, but I'd prefer to learn this stuff myself.

So what are my realistic options?



Again, if we can keep the topic to ECU options and roadblocks I will run into, I'd appreciate it. If you want to discuss how awesome this would be, PM me and I will agree with you. Likewise PM if you want to discuss my reasoning for going this route or why I don't do something else you think would be cool too.

zoom44

well you can easily run the renesis on something else but its about cost mainly right? whats the cost of a rene and PCM versus just the rene and a standalone. Have you checked your local you pull its? Someone should drag Paul in here...

RIWWP

iTrader: (2)

Yeah, cost will be a component, I don't have the financial pockets for a BOSCH or something of that grade , but being the right solution for me means more. I refuse to just buy stuff and try it and hope it works, because it never will at that point.

IF (and I recognize that it's a very valid IF), pulling the ECU/PCM (same thing right?) from a wrecked 8, and wiring a new harness in for the engine components would actually work, then I could see that as being the most cost effective route, for both the swap itself as well as the tuning afterwards, although more work on the wiring end (but that is probably the part I have the most pre-existing knowledge about how to get right). Being a 1999 or 2000 Miata, it will have ODB2, but I do not know if it is possible to tap an 8s ECU into that properly for COBB AP tuning. I suspect that it would be, but I also suspect it wouldn't be simply a matter of running the wires over there.

No sure what you mean by "Have you checked your local you pull its?" I suspect there is one or more typos in there hiding it's meaning

Solidtrance

iTrader: (2)

I think he means to check Pick and Pull type of Junk Yards in your area to see how much an RX8 ECU/wiring harness would cost. Using an RX8 harness/ECu combo will be great if all the connections can be made to work. Should be the easiest way to get the dash to intergrate. Matter of fact it would be cool to get an RX8 dash cluster and install that as well. Seems like doing this with an NC miata m9ight be easier as it already uses the same trans. Might make the intergration easier. I don't know enough about the miatas to be sure.

RIWWP

iTrader: (2)

Yeah, an NC chassis is ideal, as it has so much in common with the 8. It's almost a plug and play with fabbing new engine mounts.

But my financial resources rule out being able to get an NC for this. I'd have to get another 4-5 year loan and back into car payments. An early NB is less than $150 a month for a couple years (though I'd still pay it off in a few months tops before starting the swap). Not going to do a swap on a car I'm still paying on. An NA's engine bay is smaller than the NB, and quite a bit more work, though the e-shaft sits higher than it should in both (though closer match in the NB than the NA). So it's either wait another 3-4 years minimum and re-start it with an NC, which I don't find appealing, or start with an NB, which I'd prefer as the chassis in the end anyway (lighter, smaller, more appealing than the NC)

Done properly it even looks like a mini FD, where the NC looks more like a scalped vw bug.

An 8s gauge cluster is something I would like to do, but I am not going to let that hinge a decision on ECU. If it works with the right solution, I'll do it, if not, I'll stick with the NB cluster.

RIWWP

iTrader: (2)

But yeah, an ECU designed for the engine > an ECU that you have to get to work with the engine in my book.

I am still researching prices, but if the work is similar and costs aren't much higher, I'd considering buying a new RX8 ECU for this. I've heard they run around $1800 to $2300 from the dealer.

I've got a PM over to Danny in Aus asking what he did for this, and what challenges he faced.

RIWWP

iTrader: (2)

...and just found the 1 line in that whole thread mentioning his ECU choice. A Motec M800. Still interested to find out what challenges he faced and why he picked that.

kartweb

I'm a big fan of MoTec having used their systems for controllers and data for many years. The downside is by the time you've bought and configured the system you'll have probably spent as much as you did on the car and the engine.

The OEM ECM & cabling is already programmed and relatively inexpensive from a recycler.

RIWWP

iTrader: (2)

Thanks. That is the feeling I was getting as well. Been researching the MoTecs, and I think it might be buying way more than I need to get what I need, if that makes sense.

zoom44

yeah you could run the rene on a Motec M2R

http://www.motec.com.au/m2r/m2roverview/

interesting prices

http://www.racingbeat.com/motececu.htm

but if you are going to source a used rene i was saying you should get the wiring harness and pcm (and dash for tht matter) from that car. one big package all already known rto work together.

otherwise go the motec M2r route

alnielsen

iTrader: (4)

A RX8 PCM is going to expect input signals from sources that aren't present on a NB, right?

zoom44

yeah but if you've got a cobb most of that stuff can be dealt with.... hmmm welll actually if its expecting input from DSC or TC and it gets none it would limp right? Dont think the Cobb can adjust that. sooooo

RX-8 PCM from an early base that had none should work. What else would it be missing?

TeamRX8

iTrader: (25)

The early base models didn't have TC/DSC so I don't see that as an issue.

I have a new takeoff ECU from a 2005 6 speed that I purchased direct from Speedsource and never did anything with if you need it.

bse50

The m2r only supports 4 injectors. I would source a wrecked rx8 and remove the ecu and the sensors\wiring stuff needed to do a complete swap. You could also swap the differential and the transmission at that time, probably making the complete build easier.

zoom44

oh right. missed that

bse50

Yep but at that point i'd personally consider other roads!
PhillipM enlightened me with this cool ECU some time ago on another board (he's also a member here) : http://www.dtafast.co.uk/S_80_PRO.htm
It's not the best system out there but is not crazy expensive and can be worth a look for a street driven vehicle.
The problem with most motorsport ECUs is that they have a ton of useful features for a track car while completely forgetting about street tuning etc. That's an example of a good compromise imho!

RIWWP

iTrader: (2)

Might take you up on that.


So it is looking like a base model ecu, preferrably from the same car as the engine, if possible. Since it will be street driven as well, i wouldnt mind having tsc/asc/abs, but realistically, its probably a lot of extra work.

I dont think i have to change the tranny/diff, since it isnt much more power, and less torque, that the turbo 1.8l miatas. I probably would change the diff though, especially if the miata i get doesnt have lsd, but the gearing might be sub par, and changing the final drive allows an easy chang there. I dont see a problem with a 5sp transmission. Might even be better. I believe the 5spd is preferred for miatas for autox anyway.

Symbioticgenius

S2 Renny have 4 injectors, so I think Motec M2R would work. If finding one of those is a possibility, The S2 Renny I mean

RIWWP

iTrader: (2)

Danny brought up a good point about ECU. He decided not to go with an RX-8 ECU since it wasn't plug and play, and it would be looking for the Immobilizer, electronic steering rack, ABS/TCS/DSC. And probably a few others.

I can remove the TCS/DSC going with a base model, but the electronic steering and Immobilizer are on them all. Fortunately it looks like ABS is available (if not standard) on the NB, so it should just be sensor hookups. I expect COBB probably didn't even research the steering or immobilizer. I am going to chat with another member that hacked open a 2004 ECU to play with everything to see how much, if any, of this can be disabled in the ECU. If these can't be disabled or bypassed, I will probably have to obtain the entire harness with everything, which does mean more components to install, Doable, but just got tougher. And another reason that the NC is an easier chassis for the swap, since it has more crossover to the 8 (like the standard immobilizer)

bse50

Have you considered the ECU that I posted earlier in this thread?

alnielsen

iTrader: (4)

Racing Beat's race tune disables the immobilizer.

RIWWP

iTrader: (2)

Whoops, completely missed that. Clicing into it now. I will consider everything that is within affordable range, and won't rule out anything until I can solidify that a given ECU won't work for me. What is left is my true options and there I can start nit picking ease of use etc...

Good to know, definitely means that it can be bypassed, which makes it more likely the rest can as well.

yiksing

Just curious, why a Renn?

Mazmart

iTrader: (12)

The costs and complications that I forsee doing this in an NB chassis may exceed doing it in an NC. If money is a factor then this may not be a wise project.

I'm not sure if anyone has outlined just what makes NC so perfect for the Renny swap; okay, Ill reveal most of my secrets:

The architecture is the same allowing the engine subframe to bolt directly in place.
The exhaust is on the correct side so the PPF can be used with some modification.
The gearboxes are the same length although different manufacturers (6 Speeds).
The driveshaft plugs right in (MX5 into RX8 gearbox).

Those are a few advantages.

I bought an NB to do a rotary swap and stopped. I was overjoyed when the NC came out as I guessed very early on that the interchange potential would be high.

Best of luck with whatever you do.

Paul.

RIWWP

iTrader: (2)

I believe the Renny is superior to prior rotaries. Parhaps there is more information and practice going FI on prior rotaries and you can get more power out of them that way, but the NA stock Renny produces the ideal amount of power for a 2200-2300lb car. I am not power hungry or power crazy, and believe that there is such a thing as too much power, more so for a car that will be used on the street as well. I could go FI on the Miata engine for similar power levels, but I really love the tactile and audible pleasures of the rotary, not to mention the lower torque and wider power band of a 200whp rotary vs a 200whp I4 turbo. Lower torque isn't a problem in a car of that weight, and more of an advantage since it is easier to keep traction.

100% agree that it would be easier with the NC. There are additional advantages of the NC beyond what you mentioned that I have found as well. I would prefer the NC for that reason. But the cost of an NC is still too high. I can forsee spending $8k-$13k on the entire project, including the cost of the NB and the engine, selling the 1.8l from the NB, etc... but the cheapest undamaged NC I have found so far is $11k by itself, vs finding suitable 99-00 NBs in the $3,500 to $5,000 range.

Again, one reason I am doing the research and planning now, and I am building a document of everything I find that will be needed to take into consideration/purchased/fabricated (and I know there will be stuff that will be run into during the swap that wasn't considered or noted). If it is determined that the project ill be too hard or costly, then I will postpone a few years and let the 2006 NCs drop farther in price. $6k-7.5k extra just for the chassis vs $6-$7.5k more for chassis modifications is really the dividing line. Although I would prefer an NB over an NC in looks and size/weight for this, I am attempting to keep that in the not-really-a-factor pile for the purposes of this project.

Part of that determination will happen after buying an NB, so I can spend time measuring and investigating that chassis in my own driveway, and I leave open the possibility of leaving it alone while I wait for an NC if it comes to that. I still want a Miata for autocross/track regardless of the power plant So buying the car itself isn't a point of no return.




So far though, it is looking like an RX-8 ECU w/ entire harness might be the best route, for both cost (comparable or cheaper) and suitability for the renny. (Regardless of the chassis I end up with)

I am not making that decision now, just acknowledging that things are pointing that direction more than they did when I started the thread.