EVOllie

iTrader: (10)

My aem wideband is about 6 months old and has seen several tanks of c-16/pump, never straight c-16. Because i knew the senor wouldnt take it.
On my way to atlantic motorsports in gaithersburg to get dynoed (cool guys by the way) i did a 4th gear pull and my gauge was reading 11.6 which is were i like to keep it.
Got there did a pull on the dyno, and there gauge read 10.5-10.8 in 3rd! i dont doubt there wide band cause they dont have a rep of blowing cars up, but i didnt want to lean it out if one gauge is telling me its already leaner. when i left i did a 3rd gear pull...AEM gauge read 12.0 Which in 3rd, is normal.
My question is has anyone had there AEM guage read that far off another wideband?? The guage does not stick and reads consistent and linier. i know these gauges are cheap compared to others, but if its going to be over a point off. thats junk to me.

notes: my gauge is tapped on the down pipe where its still vertical. They tapped theres where my o2 simulator is.

Aby@MIL.SPEC

iTrader: (161)

How far apart; in inches, were the 2 sensors? I am not suprised to see differnt readings, by your description, your talking almost ~30-35".

I have seen a decent difference, 5%, when the 2 sensors were about 4" apart from each other. Granted, the tailpipe wasnt very long & the sensors due to fitment were placed in their location due to chassis constraints.

you mentioned your after dyno a/f was leaner than the prior to your dyno, did they tune the car or are you implying your encountering different readings?

12.0 vs 11.6 is only ~3.5%, ambient temps can acount for 2% easily if there was a difference in temps from your observations.

EVOllie

iTrader: (10)

The space between the 2 sensors shouldnt have made the reading that far off. one sensor is reading 10.8 the other 12.0. Thats a big differance. The 2 sensors were about a foot and a half apart.
Ive seen widebands tapped on the downpipe and dynos stick theres in the tail pipe in a supra, thats what? 8 feet apart? And they would only be +/- .1 differance
No i didnt tune the car i left it at 10.8 acorrding to the dyno. because my gauge was reading 12.0. I didnt want to take a chance that my gauge is right.

Cirrusly Evolvd

iTrader: (44)

Unless you have a leak in your exhaust you shouldn't see any difference in A/F's. Air/Fuel ratio is based on mass. The mass of the exhaust gas does not change between two points unless there is a leak in between those two points. (Physics)
It's entirely possible that one of the two gauges is wrong...it's also possible that you have a bad seal between your downpipe/testpipe or testpipe/catback.

EVOllie

iTrader: (10)

And sorry if my post was a little confusing. When i was saying i "did pulls" i was referring to doing pulls on the street.

On street with AEM wideband:
3RD 12.0 afr
4TH 11.6 afr

At the dyno with there wideband:
3RD 10.8 afr

EVOllie

iTrader: (10)

no leaks. i usually stick it up on my freinds lift to check. i hate exhaust leaks. I know one of the sensors is off, but you would think aem would have a bad rep if there gauges were THAT far off. I just wanted to get some others input before i go to another dyno and buy a new sensor.

Ev0ikon

iTrader: (18)

Your only option is to borrow another probe/WB and check it against that. It's really hard to tell if you only have 2 data points to compare. Was there any other car on the dyno that day with their own WB reading?

EVOllie

iTrader: (10)

thanks for all the info so far guys. But i know what to do far as checking against other widebands, going to another dyno ect..

I just want to know if anyone is using a AEM wideband, and having inaccurated readings. But if no one has had this problem, i'll keep you posted when i get some time to check it out.

All my 1000+hp supra friends say its definitly the senor, but they all run FJO's i figured some EVO owners on this forum would be running AEM widebands. I know they crap out and stick after running leaded fuel but I never heard a sensor not giving any signs of crapping out and just be off like mine is.

jfitzpat

FWIW:

The gauges aren't based on air mass, they measure lambda, by basically oxidizing the exhaust until stoich results are achieved inside the sensor chamber. This is a relative measurement and depends on things like partial pressure. AFR is then computed using a fixed stoichiometric fuel multiplier (ex. 14.7). So, the AFR value is an estimate, but the lambda value - where the mix is in relationship to stoichiometric, is a direct measurment - which is fuel and blend independant.

Also, lambda is continously changing. Fuel distribution isn't perfect, weak sparks happen, etc. Different controllers have different measurement speeds and feedback systems, so some variation between gauges is to be expected, particularly when a large change is occuring (ex. changing from closed loop stoich to WOT).

Still, I agree with your conclussion, variations this large are almost always plumbing or sensor problems. It is a lot easier to exceed the max bung temp than most people realize. Once you get tiny cracks in the sensor plate air leaks are common. It is possible to detect this condition, but most controllers do not.

-jjf

Edit: Also, because of the way the sensors work - they can effect each other's readings when operated in relatively close proximity.

Aby@MIL.SPEC

iTrader: (161)

give aem a call. Maybe they might swap out the sensor for you if its fairly new.

EVOllie

iTrader: (10)

I doubt it. the first question they'll ask me is "did you run leaded fuel?"

I thought running like a 60/40 mix of c-16 and 93 pump would save the sensor from the lead. But i guess not. Ive seen sensors go up, but its usally stuck at one number, or it reads real slow.

Im waiting on the new sensor i'll let everyone know if it fixes it. im hoping my air fuels go from 11.8 to 10.4 when i change it, that will answer all my questions. and it means i got more power to squeeze out.