ghia nut

Long story short.
Bought a programable ecu that uses megasquirt as the interface, added 14point7 wideband, added vtpms with new throttle position sensor.
Got car to run and start, allbeit like a 2stroke weed eater.
Any who a "life changing event" occurred and my priority shifted from hey lets take the time to learn how to tune this ecu, to this thing needs to run right now so that my wife can enjoy her car.

So I reverted it back to stock. Stock ecu, stock throttle body, stock afm :(
However I did make it to where the only pain in the *** would be to do a tb swap for automatic tb for vtps as well as resoldering the weatherpack connector for the wide band so the stock ecu would be happy.

The car runs great now and was like it was never even touched. She can drive the car and life is good.

Im just wondering about that single wire o2 sensor though. The 14point7 unit came with a simulated narrow band output.
The stock o2 sensor is a single wire so its "fidelity" is probably not any where near the modern unit and if I were to guess is not really super acurate as its just varying resistance based on exhaust output. Also is it just a simulated output or is that simulated output actually working in the way the original o2 was designed and operated with the stock ecu?
The controller for the 14point7 is just laying in the car hooked up but not communicating with anything and yes I took off the o2 so it wouldnt catch anything on fire . Could I run the simulated narrow band output and the car run ok so that when the time comes I just have to swap in the throttle body?

Bronson M

iTrader: (1)

Yes..... In a nut shell the simulated NB output is just that, a simulation of a NB based off of actual AFR's. You've got most of your other assumptions about the NB wrong but it doesn't matter, hook it up and put some miles on her.

ghia nut

Well, there's a pretty Stark difference between narrow and wide band and how they work soooooo...
But I didn't know if there would be a huge difference between running simulated and actual wideband for the car thus the questions. Like is it going to really harm the engine or just run a little rich.

Bronson M

iTrader: (1)

Well there is a huge fundamental difference between a narrow band and a wide band and an ECM has to process those signals completely differently.

This is the voltage "curve" of a narrow band, notice it's 0 to 1 volt.


As you can see it's not a curve at all, it's basically a switch that flips across .45 volts at 14.7 to 1 AFR. That's the only AFR a narrow band is accurate.

This is a typical linear wide band curve, notice it's 0 to 5 volts.

This sensor will tell you with accuracy the AFR between 10 and 20 to 1.

The factory ECM is looking for a switching .45 volts, as long as it sees the NB swapping back and forth across .45 rappidly then it knows it's at 14.7. The ECM will go open loop any time the engine needs to be richer than 14.7. so the ECM is blind to the actual AFR. As you can imagine the software routine is completely different for each sensor and you can't go ***** nilly swapping one for the other.

The aftermarket knows that a lot of people want a WB guage but still run a factory ECM and aren't interested in welding in a second bung to run two sensors so they build in circuitry that will simulate the NB voltage swing across .45 volts whenever the WB sees 14.7. In your case the WB signal is completely wasted until you hook up the Megasquirt that has the software to actually is the WB signal.



Said all that to say, hook it up, it'll run just like stock.

ghia nut

This is the explanation I was looking for! Thank you.