jwx

hello, I have a 89 Subaru RX with a 13B(S4) N/a rotary in it. the guy I bought it from was running a Dellotro carb but took it off and gave it to a friend who lost it. so he got another one but the upper intake manifold is the wrong one for the lower intake manifold, but I want fuel injection anyways so that not that big of a thing. so I ask would it be better to get a parts RX-7 and swap over the ECU, wiring harness, etc,etc or get a stand alone ECU? I've never messed with this stuff before, but I pick stuff up real quick. should I just get the right UIM and build the throttle cable bracket (for the carb) and get that tuned right, or swap fuel injecton on to it?

DigitalSynthesis

My personal recommendation (and this coming from someone who has ordered but hasn't yet recieved his first aftermarket ECU!) is to go aftermarket if you have the option. The stock stuff is :



- More hassle than its worth

- Relatively inflexible at best

- Downright frustrating, picky, and annoying at worst (that's when its fully functioning!)

- A PAIN to troubleshoot

- Expensive when new, and used items are generally of unknown reliability

- Uses an AFM which can be seen in many circumstances as a disadvantage rather than an advantage



Whereas an aftermarket system such as a haltech is:



- Completely customizable to whatever injection setup you want

- Can always be retuned to fit your modifications

- Shows you quickly what its seeing so troubleshooting is much faster

- Uses reliable, time-proven GM-variety sensors

- Provides you with a guaranteed new set of wiring and sensing apparatti eliminating many potential problem areas

- Is fun, provides more power at greater fuel economy than stock (with a proper tune), and

- Uses a MAP sensor which is much less sensitive to things such as miniscule vaccum leaks and does not restrict intake airflow.



That's my $0.02.

j9fd3s

yeah if you have to wire it up in a different car the stock stuff is a big pain

jwx

but what about mapping, and stuff? I just don't want to jump into this and not know what I got myself in to. and is there a kit available for the 13B?

jwx

and this might not be the place to ask this question but would fuel injecton be better then a carb setup(ie, dellorto,webber,mikki(sp)holly?

DigitalSynthesis

You can get base maps for almost all major ECUs for your car which will start it up and give you a good base to begin proper tuning, and there are a lot of competent tuners to help you get a solid setup.



I *believe* fuel injection is better, but there are plenty of high powered RX-7's running on carbs. I'm not one to comment since I've never really seen a carbed vehicle so I know nothing about them. Fuel injection is vastly more controllable though and I think you get better fuel economy as well. But that's all theory coming from me.



edit: redundant signature

j9fd3s

yes, when its setup right efi will be responsive in corners, get excellent mileage, and make power on the same map.



carbs can be setup to be very close though

jwx

cool didn't know I could do that. now how about that other question. is there a kit with most of what I need? I assume I would need tohave a manifold and throttle body, but what about the rest (ie wiring, map sensor(s?) stuff like that?

DigitalSynthesis

Well, to my knowledge most Mazda rotary owners with "typical" aftermarket setups run the following:



- Stock CAS (crank angle sensor - I think you have a distributor in exactly the same location)

- Stock coil packs and built-in ignitors (they reportedly outperform pretty much all aftermarket brands and are usually durable although they are known upon occasion to die - if they aren't ridiculously expensive from mazda directly compared to a potent aftermarket unit, I'd get brand new stock coils or try some fairly clean and well-kept used ones)

- ECU-supplied or recommended MAP sensor, water temp. sensor, and intake air temp. sensor. Haltech I know uses GM standard sensors which are not only fairly reliable but are also easy to get and replace.

- Whatever pressurized fuel system you want to run. Most people use a 255lph pump such as the Nippondenso (expensive), Walbro (cheap), or Bosch (expensive and does not fit in the tank I think). You can most likely just pick up a set of manifolds, a throttle body, and fuel injector lines from some junkyard or some owner who is selling theirs (like me... ) and use those and won't need to machine much.



IIRC that's pretty much all you need to run your system on EFI. I just noticed you are in Atlanta. If you want to PM me and drop by my place sometime I can hook you up with an entire S5 NA intake and fuel setup - I'm pretty sure most of that is a bolt-on to your engine, at an excellent price with no shipping charges. Its all pulled from my NA engine before the turbo swap and fairly clean too. (hint hint!! Please I gotta sell this stuff! I'll make you a good deal!)



Have I forgotten anything critical? Oh yah the TPS on the throttle body - if you use an S5 throttle body there is a full range TPS that works perfectly for an aftermarket ECU. If not, you'll need to fab a bracket to hold the TPS.

DigitalSynthesis

Oh I forgot... the haltech at least comes with all sensors except the MAP sensor, and it also includes the flying lead harness. Most dealers sell it as a package - Haltech basic kit, 3-bar MAP sensor for turbos, 1 bar for NA, and the necessary connectors. That will let you use a setup like I just described. I don't know about the other major ECU brands (Microtech, Wolf, or Electromotive).