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Discussion Starter · #1 · (Edited)
Wideband O2 to AFR controller to ECU

Hey guys.

I installed my MXT-L AFR controller along with a bosch style wide band in my driver side bank. I need to know the voltage output from my o2 sensor that my ECU needs to read lamda (or shall I say lean/rich) as I can define this in my controller.

I found this: Oxygen sensors | Mustang Forums at StangNet . It stated that at lean it will read less than 400 milivolts and at rich it will read over 600 milivolts with an overall range of .1 to .9 volts. So I did the math and this is what I got:

.1 to .4 volts is lean
.5 volts is lamba
.6 to .9 volts is rich

I included a screen shot of the factory defined analog output voltages for the MXT-L. By FACTORY DEFAULT it's allocating 1 volt as lamda, .5 volt at full lean and 1.5 volts at full rich. I will change this to the aforementioned calculations. Do my calculations look and seem right? Can anyone confirm this information? I just want to make sure I have the right info and only need to program my controller once...
 

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Discussion Starter · #2 ·
UPDATE:

So I hooked up the analog one output on my MXT-L controller to pin #43 (Dark blue with green) on the connector to the ECU. I defined my controller to read out lambda, and .1 volts at .5 lambda and .9 volts at 1.5 lambda. During the first start she died, but the wideband was still heating so it did not give a reading. I let it heat then she fired right up. No oscillations in the rpms. I took the mustang for a spin and it appeared that she was giving accurate readings but I was mostly around the 16 mark. I logged it and attached the logged to this thread.

I did have one hiccup that was good and bad. Bad: The MXT-L froze at 22.4 while I was cruising in 3rd around 2100 rpm. The motor stuttered for about 15 seconds while it froze. I tried to put it under load to enrich the AFR and nothing... still stayed at 22.4 and bogged the motor. The meter then slowly went rich back to 16 and she ran puurrrfect Laid the hammer and she responded. The GOOD: The output from the MXT-L to pin 43 did have an affect on the motor; it's the right connection and the voltage outputs are right.
 

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Thanks for posting this, I am going to dealing with this exact issue putting my 306 back in my car (engines finally back from the builder).

I have the same wideband guage, originally I was going to install a new bung and run the wideband seperately and have the ECU read off the narrowbands like factory. Then I read the manual on the wideband and found out it does provide this narrow band output.

Is your check engine light on? I was concerned of the computer throwing a code becuase it didnt see the heater anymore for the factory o2 sensor.

Also, if im not mistaken Analog out #2 is pre-set from factory for a simulated narrow band output. What you posted in that screenshot shows analog out #1, from 0-5 volts which would be what you would use to feed an ECU that is looking for a wideband input. Basically its the defualt output you would if you were doing exactly what we are doing with a car that came factory with a wideband sensor.
 

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Discussion Starter · #4 ·
Thanks for posting this, I am going to dealing with this exact issue putting my 306 back in my car (engines finally back from the builder).

I have the same wideband guage, originally I was going to install a new bung and run the wideband seperately and have the ECU read off the narrowbands like factory. Then I read the manual on the wideband and found out it does provide this narrow band output.

Is your check engine light on? I was concerned of the computer throwing a code becuase it didnt see the heater anymore for the factory o2 sensor.

Also, if im not mistaken Analog out #2 is pre-set from factory for a simulated narrow band output. What you posted in that screenshot shows analog out #1, from 0-5 volts which would be what you would use to feed an ECU that is looking for a wideband input. Basically its the defualt output you would if you were doing exactly what we are doing with a car that came factory with a wideband sensor.
Awesome! I posted this thread to help someone who was as clueless as I was haha. My check engine light is not on from the wideband. With the MXT-L you can define what you want the output to read in (lambda or AFR) and you have the ability to define the voltage output for the said reading. The picture I posted was of the default screen, I have since changed it to .1v for .5 lambda and .9v for 1.5 lambda which puts the x and y axises at .5v for stoich. I saw that the analog #2 was already defined for lamda, but since I needed to change it anyways, I just went ahead and made #1 what I wanted. I'll try to get another screen shot of it.
 

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.45 volts is the crossover point and lambda (~14.7 AFR) in a fully-warm early Ford EGO sensor.

Lean is less than 450 millivolts (.45 volts), and rich is more than .45 volts.

My HEGO's tend to stay below .4 when even slightly lean, and above .6 even when just slightly rich.

The problem is the narrow EGO sensors are not linear, they behave partly like switches. I built a warning system for my car that samples the HEGO's. My home made system looks at the HEGO's and other things just to give me a warning idiot light. It considers any fully open throttle voltage below .55 as lean, because I want things on the rich side at WOT. It inhibits giving a warning on any closing throttle movement.

I did this because my Innovate LM2 with wideband was so unreliable, and I wanted fail safe warning lights. When the LM2 locks up, and it does at times, it can lock with good mixture.
 

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I'm wondering if I should just install the other bung now and do my original plan of running both factory narrow bands, and leaving the wideband completely standalone.

All this talk of them "locking up" kind of has me worried. I don't want my car to start running like **** at 70mph on the highway, have to pull over and cycle the key just to keep on going because a GUAGE decided to malfunction.

Old man, what is your homemade setup? Are you even using a wideband?
 

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Correction to my previous statement, my check engine light IS on.
Okay, do you know if that's because you are using the wideband to feed a signal into the ECM and its not "seeing" the original o2 sensor?

Or is it on for some other reason?

Just curious. I mean, I don't really care all that much. Im pretty sure my CEL will be on for a while anyways until I get a quarter horse tuner, since I am not putting any of my emissions stuff back in. EGR, Evap, Smog Pump, etc.
 

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I'm wondering if I should just install the other bung now and do my original plan of running both factory narrow bands, and leaving the wideband completely standalone.

All this talk of them "locking up" kind of has me worried. I don't want my car to start running like **** at 70mph on the highway, have to pull over and cycle the key just to keep on going because a GUAGE decided to malfunction.

Old man, what is your homemade setup? Are you even using a wideband?
I have a LM2 wideband, but it is somewhat unreliable. It is not the Bosch wideband sensor that is trouble, it is in the design of the LM2. I absolutely use the wideband, but the LM2 occasionally locks up when logging. I'd say 1 out of 3 or 4 times it locks and I don't log an O2 reading through a full run.

My homemade system is a series of voltage sensors that can be programmed to any voltage as an alarm. The alarm can be excluded by RPM or by throttle position.

The alarms can be programmed as a caution or as a stop. I did this because I had a couple lean outs where I lost a piston. One was from a hose cracking loose from the SC inlet, and one was from loss of fuel pressure. Even though nothing gets hurt besides a piston, a piston is expensive to replace. Now I watch oil pressure, fuel pressure voltage, the wideband sensor, the narrow band sensors, engine knock, and water temperature and assign throttle positions and RPM where they take effect.

I have gone back to a warning light system instead of gauges (gauges still there), because I never can watch gauges when going down the track.
 

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I have a LM2 wideband, but it is somewhat unreliable. It is not the Bosch wideband sensor that is trouble, it is in the design of the LM2. I absolutely use the wideband, but the LM2 occasionally locks up when logging. I'd say 1 out of 3 or 4 times it locks and I don't log an O2 reading through a full run.

My homemade system is a series of voltage sensors that can be programmed to any voltage as an alarm. The alarm can be excluded by RPM or by throttle position.

The alarms can be programmed as a caution or as a stop. I did this because I had a couple lean outs where I lost a piston. One was from a hose cracking loose from the SC inlet, and one was from loss of fuel pressure. Even though nothing gets hurt besides a piston, a piston is expensive to replace. Now I watch oil pressure, fuel pressure voltage, the wideband sensor, the narrow band sensors, engine knock, and water temperature and assign throttle positions and RPM where they take effect.

I have gone back to a warning light system instead of gauges (gauges still there), because I never can watch gauges when going down the track.
Yeah, I went ahead and just welded in the bung for the wideband, so the ECU wont be relying on my MTX-L for a left cylinder bank AFR reading and instead just run how it was designed.

This way if it does lock up while I'm driving, I can just get pissed off and keep driving. Instead of getting pissed off and the car also running like crap.

I definitely don't need to run that crazy (but cool) warning light setup like you but at the same time Im running a N/A 306 setup. I may mess with nitrous down the road but it wont be anything too crazy and it wont be for a while. I just want to see how reliable my MTX-L is before I trust it warn for a dangerously lean condition with nitrous.
 

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Discussion Starter · #11 ·
Okay, do you know if that's because you are using the wideband to feed a signal into the ECM and its not "seeing" the original o2 sensor?

Or is it on for some other reason?

Just curious. I mean, I don't really care all that much. Im pretty sure my CEL will be on for a while anyways until I get a quarter horse tuner, since I am not putting any of my emissions stuff back in. EGR, Evap, Smog Pump, etc.
I do not believe the CEL is on due to the MTX-L as that it is only replicating the output voltage of the OE narrowband. I'm still having issues with it freezing on me. :-/
 

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I do not believe the CEL is on due to the MTX-L as that it is only replicating the output voltage of the OE narrowband. I'm still having issues with it freezing on me. :-/
Yeah, I went with my original plan and just drilled and welded in a separate bung for my wideband, right behind the passenger side narrowband to avoid to the whole freezing issue effecting the engines performance.

So far my MTX has yet to freeze up on me while it was running...then again I only got to put 200 miles on my mustang before one of the rocker studs snapped on me, lol.

If its feasible for you, you should do what I did and weld in a separate bung and isolate the wideband from the ECU this way even if it does freeze it wont effect your engine at all...completely standalone.

Who knows, maybe that analog output the MTX is sending is not playing nice with the ECU and causing the MTX to freeze? Just a thought...
 
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