Debate: Closed Loop vs Open Loop - Narrowband vs Wideband

[SiriusC1024]

I've wondered about that, too. Maybe there's a hysteresis component that's making the difference.

[horsepowerguru427]

No. If they match up, and the narrowband O2's are doing their normal full range switching, then nothing to adjust.

No, i meant if they arent matching up. If they arent agreeing with each other and there is no adjustment for the WB then what would be the solution? Differnet WB? Change switch points? Which one would be relied on as more accurate in that situation?

[SiriusC1024]

Check that narrowbands are switching correctly first. Then it's narrowband fuel trims that you want to use. Usually the wideband comes inline at higher RPMs and loads.

[GHuggins]

No, i meant if they arent matching up. If they arent agreeing with each other and there is no adjustment for the WB then what would be the solution? Differnet WB? Change switch points? Which one would be relied on as more accurate in that situation?

Play with inj timing and O2 settings to bring them more in line with one another first then you can use the trims for dialing it in. A 4ish % difference is all you really want. 3rd gens are harder to obtain this only because there isn't a distance setting in hpt that you can change.

I believe you've already seen Alvin's write up for fixing or rather correcting the offset issue that "noise" (temperature, wire resistance, terminal tension and so on) creates in analog circuits if your gauge face doesn't agree with the scanner's display. If necessary you can create multiple ones to correct for rpm and voltage load changes.

[horsepowerguru427]

Im sure i have read it. I read everything i can get a hold of when it comes to tuning. Might give it another look soon though, never hurts to refresh a subject.

I only posed the question out of curiosity. Most of the cars i tune are mild builds so using trims on the low end is possible and usually gives me better drivability. I have mostly used WB on the high end for WOT and comparing mid-load range with the trims, but i cant say ive ever noticed a big discrepency in the readings. Nothing that caught my attention anyways... Maybe i should pay more attention XD

Thanks for the input though, fellas. As always, i appreciate it.

[TheMechanic]

I thought of one more thing. Maybe someone can chime in. I know that the lean to rich switching rate on a typical O2 sensor according to the CARB when I had my smog license is from under 175 millivolts to 800 or more millivolts in under 100 milliseconds. I wonder if the WB has a slower response rate and will do more averaging. Or vice versa it has a much faster switching rate. Thereby giving different results on AFR.
I am thinking that the WB has to first respond to the AFR it sees. Then its analog signal is processed by an electronic device (AEM gauge set) then the analog signal is processed digitally then processed a second time by the computer, and a third time to a digital signal for the scanner, then processed to something we can actually view. That's a lot of bottlenecks.

[GHuggins]

If that was the case it would be worse at higher rpm. I still stand by the engine is calibrated for a stock setup and once that is changed everything using airflow variables for control gets shifted and then the wideband becomes the constant. Plus look at all of the calcs that take place within an ecm. They don't seem to have a problem with bottle necking unless you just completely screw up one of the root calcs which is easy enough on the newer ones and then things can go south real quick. Nevertheless the O2's are what the ecm is using for fuel corrections, so correct them as much as possible and then go off of trims until wot PE comes into the picture at which time use the wideband.

[SiriusC1024]

Maybe maybe not. At higher RPM exhaust flow is more consistent. That's what the the airflow modes are for with the narrowbands. Wideband controllers lack any such set of modifiers.