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I am having issues getting the afr correct when using closed loop fueling. Basically, my typical idle is as per the screen shot. I have 14.7 as the target, but the o2 voltage is reads rich yet my wideband reads lean. The narrowband lean / rich cross point is set at 0.5v but during idle it always reads higher as if it should be rich. Also, to make things even more confusing, the ecu is pulling fuel out as can be seen.

So basically the closed loop is pulling fuel out, making the actually afr run leaner than target afr, but the o2 sensor voltage is in the rich range? Are there some parameters or offsets I need to look at? The only thing I can think of is the airflow at idle is different for my engine being a 355ci with cam compared to a standard engine for which the tune would suit?

Which tune are you using and has it been altered to suit the engine?

do the AFR's (NB Vs WB) match when cruising in closed loop mode?

The base tune was originally the one that came with the nvram chip. But have changed the lean/rich criss points to 0.5v and lean /rich voltages ro 0.4 for lean and 0.6 for rich. The numbers are better when cruising in closed loop. I dont get many cross counts though and it seems slower to react compared toy old Haltech. It is the same o2 sensor.

If you change the voltage settings than the readings won't be accurate.

I've always thought that closed loop had no effect at idle, even with a target of 14.7
NB O2 can be slow or innacurate at idle especially with extractors fitted.

Where's the wideband fitted? Are they measuring different cylinders or further away?

I'd go off the wideband reading and add a little more VE. Does your wideband controller have a fixed voltage output feature to help calibrate the 0 to 5 volt at the ECU?

I would think either the idle afr tables has 14.7 values or its not going into idle afr table .....

personally i'd be making sure its not going into closed loop at idle and then using the wideband to dial in the idle fuel, then if you want to use closed loop idle after that you can, but I'm not sure why you'd want to as apposed to using the normal idle afr table ?

also keep in mind closed loop fuelling is different to closed loop idle.

Yeah, the standard engine really idles quiet rich, I wonder how much of that has to do with the heat from the banana's manifold?

Is the wideband 0-5v offsets set?
Is the wideband measuring the opposite bank or somewhere different to the narrowband?

immortality wrote:If you change the voltage settings than the readings won't be accurate.

I changed it to 0.5v as the original voltages were on the lean side. My understanding is thant narrowbands cross from lean to rich at 0.45 or 0.5v, i had 0.5v set on the haltech and that was fine. However there might be other offsets that I have not taken into account with the delco.

Dylan wrote:I've always thought that closed loop had no effect at idle, even with a target of 14.7
NB O2 can be slow or innacurate at idle especially with extractors fitted.

Where's the wideband fitted? Are they measuring different cylinders or further away?

I'd go off the wideband reading and add a little more VE. Does your wideband controller have a fixed voltage output feature to help calibrate the 0 to 5 volt at the ECU?

There is closed loop idle which controls the IAC and closed loop idle fuelling which controls the fuel amount with the narrowband sensor.

The sensors are in differenwnt locations which is something I considered except that the Haltech was spot on 14.7:1 on the wideband when the narrowband sensor was being used during closed loop with that ecu.

Yes the wideband has a fixed output that is running to the ecu and I have checked its calibration with the gauge read out.