scesare1

As title states I have a S4 TII with stock ecu, dude I got it from claims it has a half bridge port. I have a apexi safc installed and figured that's what was causing my problem. My car will not idle and has horrible horrible throttle response on lower rpms ~3500. If I add alot of(25%) fuel with the safc on the lower rpms it'll idle but still very bad throttle response. It also has 550primary 1000secondary. So my question is will a half bridge not run on a stock ecu and do I need a new management system like haltech, or do I have a problem with my primary injectors not providing enough fuel(clogged or went bad causing me to have to add more fuel to idle). Or something wrong with my tps causing my horrible throttle response. I'm clueless so PLEASE HELP

fendamonky

iTrader: (6)

I'd swap out the ECU for something modern if I were you... I'm not sure what the factory injectors are meant to be, but I'm thinking that if you've changed them around than the factory ECU may not be happy. Same thing applies for dramatically changing the porting while running a factory ECU...

I'm not an FC guy though, so I don't know how flexible the 2nd gen systems are.

jjwalker

I can tell you right now that you cannot swap injectors like that nor do a bridgeport on a factory ecu. The car runs like **** because the ecu has no idea what the hell is going on. Firstly, the factory ecu assumes you are running stock injectors and has no idea you have gigantic ones on the car. Secondly, beyond a street port, the ecu cannot reliably run the engine because the overlap and airflow characteristics of a bridge port is way outside of its lookup table

scesare1

So that's my problem then? I need to ditch the safc and the stock ecu and buy a stand alone like haltech? This would cause the good awful throttle response?

jjwalker

Yes.

Here is a good way to picture what is happening. Imagine you have a multiplication table that will give you answers from 0 to 100. Take two numbers and cross reference them with the table and you should get an answer right, well what happens if you answer is more than one hundred?

The second gen ecu is really stupid really. It takes in all available sensor data and does a lookup on a table to determine spark timing, fuel, etc. That table is based on what sensor input values it would get on a stock engine. It has enough play so that changing exhaust or putting in a higher flowing air filter isn't going to wack it out.

I suggest going over the the second gen specific section and speak to them about what some good options are on an aftermarket ecu.

fendamonky

iTrader: (6)

If I may add in... DON'T just get the cheapest ecu that will work. Pay the extra cost now to get a GOOD current ecu that will serve your purpose for years down the road. If you cheap out now on an older (mid-90's) ecu there is a good chance you'll be replacing it shortly down the road anyway. Spend a little more NOW to save yourself a headache and rework down the road.

j9fd3s

iTrader: (3)

the stock ECU is programmed for the stock engine, and it can handle some mild mods, but i wouldn't expect it to be able to run a bridgeport, and even if it did, it wouldn't be very optimal

scesare1

Thanks for all the input, very helpful! I'll hit up the 2nd Gen section for ecu info

Aaron Cake

iTrader: (1)

Might be a good idea to find out if the engine is bridgeported before you go swapping ECUs if you don't have to. A standalone is large investment. Figure you will spend between $1000 and $1500 (but could be more) before tuning.

If you pull the lower intake manifold (yes, I know this is a pain) you can look into the intake ports with a light and mirror. Bridges will be obvious at that point.

fendamonky

iTrader: (6)

I'm not sure how you're calling an ECU a "large" investment, cost wise, considering how important it is. $1,500 is lower in the bottom half of the spectrum for good ECUs...

Which is cheaper, a quality ecu, or a COMPETENT rebuild???

Aaron Cake

iTrader: (1)

Large in the sense that the OP may be thinking that an ECU may be a chip like many other vehicles, or a simple piggyback.

$1500 is easily doable with a Megasquirt MS3X once all wiring supplies are factored in.

Of course that doesn't include the necessary wideband.

And if the OP isn't familiar with tuning, then he'll be paying for a tuner at $100+ per hour plus the cost of dyno time.

It all adds up. That's why I suggested making sure the engine is bridgeported before going down that road.

scesare1

What makes me skeptical Is my buddy who has been into rotary longer than me says it doesn't sounded ported. Can a half bridge not run off a stock ecu? Not even idle? It'll only idle if I turn the fuel up on my apexi safc. I was planning on going with a haltech sprint re that's$850

scesare1

I also have a innovate lc1 wideband. It runs lean 14-15 and wont idle until I turn up the fuel and get it to idle at 10-11 on my wideband

KNONFS

iTrader: (14)

The Sprint RE is a great unit, you wont be disappointed (Talk to C.Ludwig about it )

Even if your engine is not ported, an aftermarket ECU is the way to go in my opinion.

fendamonky

iTrader: (6)

This is pretty much the point I was trying to make.

scesare1

My Luck ill get this sprint re and something else would be wrong with my motor making the throttle response bad like it is

Aaron Cake

iTrader: (1)

Yes, a Bridgeport can run from the stock ECU. Well, absolutely not. What it requires is a large set of primary injectors because bridgeports will typically require twice the amount of fuel as a stock ported engine to idle. The only way to achieve that with a stock ECU is to slop in some bigger injectors. The result of course is that the car runs terrible everywhere except at WOT. It's hard to start, fouls plugs, pig roots in traffic, bucks, sputters, etc.

A larger set of a injectors and an S-AFC to control them could get the car running reasonably OK. Reasonably OK. Not well by any means and since the S-AFC has only narrow control of the fuel then there are many instances where the car will just be massively rich. Such as startup. That completely ignores the timing changes needed to properly run a Bridgeport which are above what the S-AFC can accomplish.

The spring RE is the most basic of Haltech ECUs. I'd suggest going up one to the Platinum 1000 as you'll get far more I/O which you probably won't use immediately, but will want to in the future. Also the ability to control an idle valve which will be VERY useful for fast idle during warmup (though can't really regulate a Bridgeport idle once warm all that well).

However, as I mentioned, confirmed it is bridgeported with your own eyes before deciding a specific direction.

All the people saying to get an ECU are forgetting that wiring one up is the easiest part. The car then needs to be tuned, which is where the skill lies.

silverTRD

iTrader: (36)

Yes an ecu will be a good upgrade, but wouldn't you like to know what port you have reguardless? A tuner will want to know, that's for sure.

What if your car isn't ported? Then there is obviously a problem that may not be the ecu. You should troubleshoot before you throw money at the problem.

scesare1

Sounds like my problem exactly. It wants to flood at start up but won't idle unless I give it fuel from the safc. But has horrible throttle response under 3500. How exactly do I figure out what port my 7 has?

scesare1

And lets say my car isn't ported. Where she could I look to fix the problem

bumpstart

1987?

seriously, no one bothers with those old ecus anymore cause of exactly this vagueness and untuneability

Aaron Cake

iTrader: (1)

Referring to post #9 in this thread, you will need to remove the lower intake manifold and look into the intake runners on the block. From there it will be very obvious if they are bridged. Or if not bridged, you can at least get some idea if port work has been done. Now it takes an experienced eye to tell the difference between other types of port from this view so pictures posted to this forum would help. Use a REAL CAMERA, not a phone and use the macro featured with lots of light.

scesare1

Is there a write up on that

Aaron Cake

iTrader: (1)

The Factory Service Manuals for all years of RX-7 (and many other rotary cars) can be downloaded for free here: Foxed.ca - Mazda RX-7 Manuals . They contain all common service information and more, and are an essential tool for any sort of service work that needs to be performed on these cars.

Additionally, the Haynes service manual for the 1986 thru 1991 RX-7 (both turbo and NA) can be found at most local auto parts stores or purchased from any good bookstore (ISBN number 1 56392 007 7). It is only about $25 and is a great quick reference for things like this. Not only does it contain most of the information in the FSM condensed into an easy to read format, but it includes full wiring diagrams as well.

These manuals will answer 99% of service related questions for the car and if you intend to do your own repair work, you will need at least one of them. Preferably both, since the FSM is a free download. The Haynes is a good quick reference covering 99% of questions, while the FSMs show complete and detailed procedures.