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Erratic Wideband Readings

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I have a 03 Dodge Ram regular cab with 408 and Vortech V1 Ti trim supercharger.

The wideband I'm using is AEM 30-4110. At the moment the wideband is proximately a year old.

Using HP turner MPVi2 and VCM Suite I have been making some AFR changes in open loop. After using the scanner to data log I make changes but it seems when I data log again it is richer or leaner. I get areas on the VE tables that is in the stoich range and call it good but later on data logging the AFR is off target again.

While data logging the wideband and the VCM scanner show the same AFR. When in closed loop I see mostly stoich readings so I'm thinking the wideband is reading the AFR correctly.

I've checked for exhaust leaks on the entire system.

Should I first try a new sensor or do I need to use a better wideband like Ballenger Motorsports AFR500v2?

Right now I feel like I'm running circles.


Hard to say, and not really my thing, but I'd suggest checking off the following.

Consistent fuel type and quality - differing ethanol percentage, if used in E' or even regular petrol (gasoline), will have slightly differing AFR/lambda. Some states use different fuel blends for winter and summer, and your 'gas' stations may be in a transition from one to the other?

Fuel pressure logging the same?

Intake temp' logging the same?

Ignition system up to the job - can't see why it wouldn't, but...?

Exhaust bypass, if used, not operating consistently, as back-pressure in the exhaust will affect breathing?

Engine temp's consistent?

Bad earth/power wiring giving varying resistances? Depending on how it's wired, accessories may even throw things off a little.

Other stuff?

Didn't realize some of things you mentioned would play a role in the AFR readings.

On consistent fuel type... I've seen the erratic AFRs using the same fuel that is in the tank.

Have not been logging the fuel pressure. My truck isn't set up for it. I've just been checking it at idle making sure it's stays consistent which it's set at 49psi.

Now the intake temps might be a issue. I've been logging on my way to work in which the intake temps have been in the 50ºF range. Then log from work and the temps have been in the 70ºF range.

The ignition is a MSD 6AL with matching MSD coil.

No exhaust bypass.

Once the engine has reached operating temperature it stays in the 198ºF range. Highest I've seen looking at the logs is 203ºF

I have the wideband's negative and HP tuner Prolink hooked to the negative of the battery.

If there is anything else on my truck that would skew the AFR readings I wouldn't know what could causing it.

Downloaded the tune today and enabled closed loop. At cruise the readings on the scanner and wideband stayed near the 14.7 reading. Noticed after data logging in the STFT there is a reading of -13 and a couple of -10s.

I don't know... I must not being doing some right.

Thanks for the help Gord