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Discussion Starter · #1 ·
Ive had the SMT-6 installed for awhile and finally got around to going to a dyno tuning shop for propper afr adjustments. Well apparently the car stock ECU is dominating any fuel settings that are entered. The stock ecu leans the AFR to 14.7 even with 100s in all fields of tuning software. I know its wired right at least that when i mess with fuel settings for IDLe it stalls the car. SMT-6 is working but is being bullied by stock ECU.
I recently installed a wideband but have no idea how to wire it into the SMT. I've read somewhere that wiring it to the wideband input on the smt will somehow fool the stock ecu and actually stick to smt-6 adjusted levels of fuel.

Has anyone run into this problem and if so what did you do to correct it?

Thanks
 

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It sounds like the O2 sensor is sending a rich signal to the ECU and that forces the ECU to lean out the mixture regardless of what the other inputs are saying. Can the SMT-6 intercept the O2 sensors and send a modified O2 signal to the ECU?
 

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Discussion Starter · #3 ·
thats what im kinda wondering if anyone has done. I know people here run the smt-6. Im wondering how they overcame it. and without a wideband how would you know how lean/rich you were. but yet im sure people run it without wideband.
 

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How much do you want to change the A/F? If you run it too rich won't it damage the CAT?
 

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Isnt the smt a full standalone? I thought you can run it that way. If you can, then **** the stock ecu. Throw it away and have the smt run the engine. All i can think is that it wont have an idle circut so you will have to remove the idle stabilizer, but you just turn in the idle screw then
 

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Discussion Starter · #6 ·
The SMT-6 is not a standalone, it's a piggyback. I need to make fuel corrections to about a 12.7 - 13.5 AFR. Im not worried about fuel economy at all. Car runs 100 octane 24/7
I also still have to be able to pass CA Smog tests.... so losing the stock ECU is out of the Question. No ECU no OBDii No Pass
 

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Another option that just became available.

I recently installed one of the new AEM FIC piggybacks on my BetaII 05 Tib with the Alpine SC setup.. This unit intercepts the injector leads and changes the factory ECU pulse width to add or subtract fuel. No trying to tune your fuel by playing with the MAF input signal. I am running a set of 34lb injectors that the FIC cuts back to the stock 190cc injector size for NA running. Cold startup, idle and hot restarts are the same as stock. The FIC has an onboard MAP sensor and I can add whatever fuel necessary to get AF I need when under boost. My long term fuel trims are holding at zero. It has the ability to modify the O2 sensor signal to keep the short term fuel trim from pulling fuel if it is needed. My factory ECU stays in closed loop at low boost levels so I am going to start using this function.
The Alpine kit came with a Unichip and 5th injector for fuel tuning. My car never ran really good with it. Getting rid of the 5th injector and going with the AEM FIC has made the car much better.
 

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Discussion Starter · #10 · (Edited)
Wychdctr,
It doesnt take very long, maybe an hour of driving till ECM corrects back to 14.7 for WOT settings and instantly on all other range settings.on the dyno the tuner added 100's to fuel maps and it made no chnge whatsoever. leaned it right back down .
I bought an o2 simulater from
https://www.o2simulator.com
I hope it works. it should be here in a few days. I will post results.
 

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When the ECU is in closed loop the O2 sensor rules. It will cut fuel with the short term fuel trims untill is gets the AF it wants.

At first I didn't use the O2 signal modification function on my FIC and the long term fuel trim would pull fuel after driving for a while. The ECU stays in closed loop during low boost and the ECU was pulling fuel with the short term fuel trims. The ECU alters the long term fuel trims based on what happens with the short term fuel trim. I don't think the O2 sensor is used in open loop but I am pretty sure the long term trims still apply to open loop fuel amounts.


After I hooked up the O2 signal modifier the long term fuel trim is staying at less than + or - 1%. With this function the FIC lowers the O2 signal voltage going to the ECU and it doesn't see the extra fuel that I add during low boost. End result is the ECU thinks the AF is what it likes and leaves the fuel trim alone.

Check this link for the turbo box that works with the SMT-6. It's supposed to force the ECU into open loop so it doesn't see the extra fuel at low boost. Sounds like pretty much the same result as changing the O2 signal.

Atelier HP extra injector spacers and turbo box GB - ElantraXD.com - Dedicated to the true Elantra Enthusiast
 
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