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Discussion Starter #1
Sorry if this sounds like a stupid question but I have to ask:

When measuring AFR the sensor is only reading one side of the exhaust and its upstream of the crossover pipe. If an injector on the opposite side or any other fuel / air malfunctions because of many other reasons, wouldn't the sensor not catch it since its on the opposite side?
 

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Yes it can happen. The best way would be to poll both banks of cylinders or monitor in real time (or near real time) and watch outputs of both. I had a problem with an LS motor once, one oxygen sensor was 'lazy' and was causing serious fluctuations on one bank of the engine.

I was also able to see a/f ratios as well as O2 sensor outputs for both sides, they were wide-band. I think the challengers are narrow band? still, you may have access to this via datalogging with a predator or trinity? I havent used one yet. hope this helps.
 

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You will get a flashing check engine light if you have a missfire (bad plug,injector,ign. coil,valve spring etc.)The computer wants to save the cat converter and will give you a warning.It will also set bank 1 and bank 2 lean or rich codes.
 

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When I was messing with LS stuff it was recommended to put the O2 sensor on the drivers side because #7 was the leanest cylinder. Not sure about the HEMI though...
 

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Discussion Starter #5 (Edited)
You will get a flashing check engine light if you have a missfire (bad plug,injector,ign. coil,valve spring etc.)The computer wants to save the cat converter and will give you a warning.It will also set bank 1 and bank 2 lean or rich codes.
RICHSRT8,
The only reason I put an AFR wide-band in was to let me know if lean conditions were occurring, I set my interceptor to go into alarm if conditions are lean at certain throttle positions. Most stuff i've read said it was imperative to monitor AFR with blown motors for lean conditions. If what you are saying is true, than I really dont need to monitor AFR since the PCM will alert me if lean or rich conditions occur?

I understand it would still be nice to have a readout to optimize performance but for strictly motor safety its not needed?
 

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RICHSRT8,
The only reason I put an AFR wide-band in was to let me know if lean conditions were occurring, I set my interceptor to go into alarm if conditions are lean at certain throttle positions. Most stuff i've read said it was imperative to monitor AFR with blown motors for lean conditions. If what you are saying is true, than I really dont need to monitor AFR since the PCM will alert me if lean or rich conditions occur?

I understand it would still be nice to have a readout to optimize performance but for strictly motor safety its not needed?
No,You should monitor A/F,just don't get too worried about reading the other bank.If you get a rough idle or missfire,check for codes.You can also monitor 1/1 and 2/1(left and right side) fuel trims with a scan tool and probably your intercepter.Usually they stay single digits +5 to -5 at idle.If your right bank was reading +15 you have a fuel issues(clogged fuel inj. etc.)Car would be lean and computer is having to add too much fuel.Sooner or later it will set a code and light.
 

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I put my Kenne Bell on late december, only now getting to the afr and boost/vac gauges, purchased the auto meter ultralites, and was reading that the afr needs a switched power circut that stays energized while cranking engine, any help on what circuts to use and locations to connect them up to, any help would be much apreciated, i also dont mind building a circut box dedicated to these auxilary circuts, if i only knew what to tap off of.
 

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RICHSRT8,
The only reason I put an AFR wide-band in was to let me know if lean conditions were occurring, I set my interceptor to go into alarm if conditions are lean at certain throttle positions. Most stuff i've read said it was imperative to monitor AFR with blown motors for lean conditions. If what you are saying is true, than I really dont need to monitor AFR since the PCM will alert me if lean or rich conditions occur?

I understand it would still be nice to have a readout to optimize performance but for strictly motor safety its not needed?
The PCM operates in two modes; closed and open loop.

The PCM only monitors AFR in closed loop via the O2 sensors, so you will need a wide-band to measure AFR in open loop.

Under normal driving, the PCM is in closed loop and takes input from the O2 sensors to adjust fueling. The O2 sensors are narrow-band, in that they only monitor AFR between, let’s say, 14.0:1 thru 15.4:1, which helps the PCM to keep AFR at 14.7:1.

During more spirited driving to include WOT, the PCM goes into open loop. While in open loop, the PCM ignores the narrow-band O2 sensors and uses pre-defined values in the Volumetric Efficiency and Power Enrichment tables to adjust fueling. Engineers know what values are needed in the PE and VE tables to keep a stock engine safe and operate at peak efficiency. So, there’s really no need for a wideband AFR sensor on a stock engine since the engineers have already determined optimum settings.

However, if you extensively modify the engine's intake/exhaust system, then your going to need a wide-band O2 sensor to determine what the AFR is during open loop. Tuners will adjust the VE and PE tables based on wide-band AFR readings. For FI engines, most tuners will try to keep AFR somewhere between 11.0 to 11.7, just depends how aggressive they want to be. Once the target AFR is met, in theory, a wideband O2 sensor is no longer needed. However, if a critical fueling component, such as a fuel pump or boost-a-pump, fails, then the AFR will most likely rise causing a lean condition. It doesn’t take long for a FI engine to grenade when a lean condition is realized, so it’s recommended to monitor AFR using a wide-band.
 
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