ml2242

Hey folks!
It's been a while since I have come here for advice for the cobalt but have recently gotten back into modding the car for increased reliability and longevity of my current build.

So, I have recently installed a brand new AEM UEGO wideband. The installation went fine and all of the wires are connected correctly but I noticed that the AFR values fluctuate an insane amount under both idle and light throttle but are spot on PERFECT at WOT. My AFR 02 sensor is connected to the bung on my LSJ manifold while my other two sensors are pre and post hi flow magnaflow cat. According to AEM my AFR 02 should be in the down-pipes pre-cat bung for optimal distance from the blocks exhaust ports. The issue is I had the car dyno tuned with the ECU 02 sensors in their current positions and my old AFR in the manifold (innovative LC-1). Would I be able to swap the two 02 sensors so that my initial ECU 02 sensor is in my exhaust manifold bung and the AFR is in the pre-cat bung? Or would this potentially mess with my dyno tune's perfection? I'm just not a huge fan of constantly flashing lights and numbers on my AFR unless im at WOT which is not all that often as this is my DD in the non-winter months.

Synopsis:
-Can an AFR 02 sensor be used in the LSJ exhaust manifold bung?
-Will the movement of my ECU's FIRST 02 sensor (has 2) from pre-cat -> exhaust manifold screw with my tuning? (movement is about 6-10 inches closer to exhaust ports than current location)
-Will the movement of my AFR 02 sensor to farther from the exhaust ports increase the accuracy and reduce the roughness of my AFR reading?

Thanks!

ml2242

Day two bump.... Anyone?

I'm planning on switching my AFR and primary 02 sensors positions so my ECU 02 is at the header and my AFR is pre-cat. Just need it to be above freezing here in Boston for a day!

nhanson

iTrader: (1)

Mine also does that. My tuner said thats just how the AEMs are. I think it has to do with air flow and that WOT is table controlled VS. computer/sensor controlled.

YelCal7

iTrader: (1)

It's normal n it should be like that. I have AEM UEGO Wideband it does the same thing. WOT it stay then drive around it fluctuate at idle or when You REV. You should put your Wideband on Your Downpipe before CAT.

ml2242

Well this makes me feel a good bit better about it

Just want to be sure my readings are relatively accurate.

YelCal7

iTrader: (1)

Yeah, It's alright. It may get annoying at first then get used to it.

nhanson

iTrader: (1)

Bring the revs up and hold it there, you will see it even out and stay around 14.7ish

ml2242

Ended up buying an 02 sensor extender so the sensor isn't in the direct stream of the exhaust and is like an inch away... will update this thread with my findings as soon as its warm enough to not bleed every time I bump into things while working on the car.

Cherry GT

Which o2 is out of the main stream of exhaust ? and WHY ?
I have noticed less swing of the afr on my AEM as my MAF tune got better.
and I agree the AEM o2 should be in the down pipe and ECM o2 in the manifold where it was originally.

ml2242

I'm a 2.2l so I never had a manifold 02, just 2 ecm 02's in the DP.... The wide-band 02 will be pulled out with the extender on the manifold....

YelloEye

iTrader: (3)

The AEM reacts very quickly to changes in the exhaust consistency, same with the OEM LNF wideband. At idle you can see anywhere from 13-15 normally, has something to do with the computer giving the cat more or less good air. You should put it back into the stream the way it was IMO, otherwise you're just measuring the past values slowly.

Validater

iTrader: (1)

Ugg. The problem here lies with the factory Narrowband sensors. Narrow band sensors can only read around stoick. but never 14.7-1.

"A narrow-band sensor has a nonlinear output, and switches between the thresholds of lean (ca 100–200 mV) and rich (ca 650–800 mV) areas very steeply."

Hence. the computer can only see a rich and lean condition around stoich. but never 14.7. So in turn. the PCM is constantly changing the STFT to keep it around stoich. This is the jumping you are seeing.

Also. being that we have 4 cyls. it isn't flowing much exhaust at idle, hence. it gets better when you rev the engine up a bit.

Final bit. At WOT. The fueling goes into Open Loop. and uses the preset injector pulse width programmed for WOT. Causing the AFR's to be steady.

ml2242

I haven't put the extender in yet... Not sure why my old innovative LC-1 was able to get such smooth values... I would assume the large block in part of the cord is doing some math to give the smoother values where as the AEM is real time... so long as it is normal.... I'm fine with it

YelloEye

iTrader: (3)

Yeah, AEM is raw real time values. Think LC-1 has a filter to smooth out an average better.

ml2242

Sweet deal. Thanks man!