???

What signal?

I fear the parallel life is not the life for you. Either start reading a lot, or forget I suggested it and do what everyone else does.

It was just a thought
not actually in parallel but using MS to output certain data (clt , iat ,cam ,crank and what ever else )in a way that would keep the OEM ecu happy and let it think its everything is fine
I guess it would be in series not parallel

Like I said it was just a thought, I dont even know if it would be feasible...kinda like using an arduino to output a set test loop to the OEM ecu while MS actually handles everything

...not saying that it's a good idea just a random thought somewhat related to the current topic

You leave the oem ecu connected to those sensors in parallel with the aftermarket ecu.

I think I failed to consider the level of knowledge that someone asking your original question has. Unless you're looking to spend a lot of time learning how things work you should probably ignore this route entirely.

Here is a thread you can check out for some info on running parallel. While it was being done with an adaptronic, you will face the same issues.

Thanks for the link Lars that was an excellent read.

Yep I remember our adaptronic days. BTDT. The level of effort to get all this to work and play nice still makes the 1 day of emissions and swapping back a drop in the bucket.
But those with the appropriate knowledge and desire should most definitely pursue this route and post their results, it is highly encouraged.

That was very helpful and explained a lot
This isn't my first venture in to this its just my first time doing it on an OBDII car
This is a bit different than 1g DSMs, 3S cars and early turbo Dodges so I appreciate the assistance on the learning curve

Don't think for a second you need an adaptronic. Any system that can run in parallel and share sensors and has enough outputs can handle the work.

Honestly everything is easy except dialing in the front O2 sensor behavior. If it's off even slightly, the car's ECU will attempt to correct and wind up the long term trim until it throws a code.

A smarter dude than I would find a way to read OBDII trims and make an O2 simulator with a feedback loop.

Don't a bunch of wideband controllers have a narrowband output as well? Seems like that would be the easy button.


Or is the issue just that the fueling is so different from what the ecu expects that it shifts the trims and throws a code?

I haven't had an issue on my f150 but it's not boosted yet either so fueling should be similar to stock right now

the ECU expects that when it sees the car is lean and adds fuel, the O2 sensor will read less lean. If that feedback loop is not respected, then yes, you throw a code. Simulating a narrowband with a wideband doesn't matter to the ECU, results matter.

Got it. I'm surprised it cares.

Maybe an arduino monitoring injector duty off the OEM ecu and outputting an appropriate signal to simulate the O2 sensor.

Living in Maryland—where cars are eligible for emissions exempt Historic status at 20—what I would do if I had a 2002 I wanted to turbo is build my car with the Voodoo Box or the TDR cards. After enjoying Some Turbo and getting OBD2 checked for 2.5 years, I would register it as Historic on January 3, 2022, and do whatever I wanted with MS3 and get More Turbo. Actually, depending on when my emissions test was due, I could do it sooner, since the test is only required every other year. So I could install a MS3 after the test date if it was 1/3/2020 or later. If that was the case, given the speed at which my projects get completed, I might not even have to bother with the Voodoo Box.

YMMV depending on your location—where do you live, OP?

It cares because that's part of OBDII. In an effort to ensure low emissions, efficient operation, the ECU monitors the O2 sensor and constantly adjusts the trim. It has limited ability to do real time trim so over time if the trims are skewing one way, it stores them to the long term trim and uses that as a new baseline.

some reading:
https://www.obd-codes.com/faq/fuel-trims.php

The arduino is a good idea. You could set it to respond to OBDII trim data and make corrections to the lean/rich duty cycle to avoid codes. It doesn't have to be fast or optimized, it can just be proportional to the size of the trim to keep it from winding up in either direction.

Aaaaand full circle.

https://www.miataturbo.net/ecus-tuni...m-trims-61113/

My coding skills are no where near what's required to do this and I have no pressing need to do it as I don't have to pass an OBDII test. Certainly looks doable though.

Fort Worth TX
25 years for "classic car" status

I guess I forgot about that post AFTER EIGHT YEARS.

But yeah, what Jason said. Just have the Arduino remember the most used correction value.