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Old 03-17-2009, 08:41 AM   #1
SubiWRX04
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Default air/fuel question

So - I installed the infamous narrowband a/f gauge (to the rear o2), and now with that thing flashing in front of me all the time, it makes me worry/begin to think that I'm running too lean... I know it's a mostly useless gauge, but I had an opening in my pod... in hangs out in lean most of the time. However, I have a data logger which communicates over OBD2 (CAN) and the front o2 sensor is displayed on the bus and is reading stoich (14.7) at highway speed and ~11.2 under wot - should I be alright?

why would the narrow band be reading so high? is it shot?
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Old 03-17-2009, 10:11 AM   #2
the suicidal eggroll
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When is it reading lean and what do you mean by lean? 14.7 while cruising is normal, 11.2 under WOT is normal only because the stock o2 sensor is useless under WOT.
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Old 03-17-2009, 10:35 AM   #3
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Originally Posted by the suicidal eggroll View Post
When is it reading lean and what do you mean by lean? 14.7 while cruising is normal, 11.2 under WOT is normal only because the stock o2 sensor is useless under WOT.
As stated - I was using a data logger to view the FRONT O2 (reading 13.4 ~ 14.7 while cruising and 11.2 under WOT) while the REAR 02 was reading in the red constantly with the exception of tip-out followed by a moderate tip-in. I am concerned about the REAR O2 - which is where the narrowband a/f ratio gauge is connected.

Correct me if I'm wrong, but isn't the front O2 a wideband AFR sensor?

Last edited by SubiWRX04; 03-17-2009 at 10:46 AM.
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Old 03-17-2009, 10:42 AM   #4
the suicidal eggroll
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What does red mean? Do you have some documentation that tells you what these colors mean?

The front sensor is a quasi-wideband, meaning it can read outside of the 14.7 range, but it doesn't do it accurately, especially since the increase in pre-turbo exhaust pressure while under boost will affect its readings.
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Old 03-17-2009, 10:50 AM   #5
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Originally Posted by the suicidal eggroll View Post
What does red mean? Do you have some documentation that tells you what these colors mean?

The front sensor is a quasi-wideband, meaning it can read outside of the 14.7 range, but it doesn't do it accurately, especially since the increase in pre-turbo exhaust pressure while under boost will affect its readings.
lol - my bad... it's an autometer ultralite gauge. red means bad (lean) - orange is stoich, and green is rich.

so basically, I could be running lean and said quasi-wideband may not/will not correct for lean conditions under load/boost?
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Old 03-17-2009, 02:09 PM   #6
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lol - my bad... it's an autometer ultralite gauge. red means bad (lean) - orange is stoich, and green is rich.

so basically, I could be running lean and said quasi-wideband may not/will not correct for lean conditions under load/boost?
"lean" meaning what? 11.0? 12.0? 13.0?
The front o2 sensor wouldn't correct for it anyway, under boost you're in open loop, which means the afr readings don't affect the fueling.
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Old 03-17-2009, 02:27 PM   #7
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Originally Posted by the suicidal eggroll View Post
"lean" meaning what? 11.0? 12.0? 13.0?
The front o2 sensor wouldn't correct for it anyway, under boost you're in open loop, which means the afr readings don't affect the fueling.
the front O2 is never exceeding approx 14.7 (i've seen 11.0 ~ 14.7) - except when off throttle/engine braking.

The rear O2 is reading lean on the gauge - which is a 0 to 0.9 v signal. So I am not sure what the AFR is based on this info.
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Old 03-17-2009, 08:28 PM   #8
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narrow bands are worth piss unless you drive at a constant load and a constant rpm and the moon is aligned with pluto and the sun has gone down. Seriously, narrow bands are purely bling gauges (although I wouldn't say the Autometer one is that bling ).

All you have to do is take your foot off the throttle a little, or drive down a slight decline and it will read lean. Even at idle it can read lean and jump back and forth - they are truely not the best at accurately reading your AFRs - and that is not including how it changes with different fuels or fuel additives.

Saying that, they can give you an idea of what your AFRs are doing, but you first have to take note of where the needle is in comparison to a wideband 02 reading - basically you "calibrate" the narrowband based on your wideband

The "calibration" process is simple:
  1. Cruise along at a constant rpm (3000rpm) on a flat road in 3rd gear, when your wideband says 14.5-14.9 check where the needle is on your narrowband gauge - that is your new "stoich" region (if running standard pump gas).
  2. Now put your foot down and when your wideband says 10-11 check the needle location again - that is now your "rich" region.
  3. Finally take your foot off the accelerator and coast/roll, check the neddle location again - that is your "lean" region.
  4. Get a marker if you need to (for ppl with memories screwed over by acid or petrol sniffing) and mark the points on your gauge - white-out/liquid paper is good as it can be scratched off at any time without damaging your gauge. A small dot at each location is all you need.

Now you have "calibrated" your narrowband gauge to your wideband readings, you'll be able to get a basic idea of what is going on. If you ever drive wot and your needle sits at the newly marked "lean" region constantly without moving (like the needle sits there for more than 500rpm), get off the gas and baby it home until you can log with your wideband again.

Alternatively, go buy a wideband gauge and be happy knowing the AFRs being shown are much more accurate
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Old 03-17-2009, 09:01 PM   #9
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I'm going to get a wideband this week - done.

however, your 'calibration procedure' you speak of... wouldn't work for me - under wot, it's in lean, under engine braking, in the lean, constant throttle, in the lean, tip out/tip in, stoich - only time I get rich is when the circuit is open lol. this is why I was asking if the circuit for the rear o2 goes high when it goes bad - because it always wants to hang out in the lean state. (and although it has been stated over and over again that these things are useless, it still scares the **** out of me when it's in the lean portion damn near all the time... I wouldn't think this would be correct)

Can someone please clarify and put me at ease here - if the front o2 is reading good values, but the rear is not, is it safe to say I'll be alright and maybe even replace the rear o2? also, I pulled the passenger side spark plugs to check how they were running, and they were a light carmely brown - I've raced snowmobiles and performance bikes for years, and this tells me i'm ok - but the o2 sensor is getting to me...
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Old 03-17-2009, 10:51 PM   #10
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Perhaps you have wired it to the wrong wire then
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Old 03-18-2009, 06:57 AM   #11
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I'm leaning towards the wiring as well. You're talking about fractions of a 1 volt making the gauge react. Any excessive voltage drop will cause the gauge to read leaner. That can happen if the signal wire is too heavy, the ground is not just right or solder connections are huge and lumpy. If you trust the wideband readings, try to dim the hell out of the narrowband display, ignore it, or get rid of it.

That's about all I can think of.....
Jay
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Old 03-18-2009, 08:48 AM   #12
SubiWRX04
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Quote:
Originally Posted by Storm View Post
I'm leaning towards the wiring as well. You're talking about fractions of a 1 volt making the gauge react. Any excessive voltage drop will cause the gauge to read leaner. That can happen if the signal wire is too heavy, the ground is not just right or solder connections are huge and lumpy. If you trust the wideband readings, try to dim the hell out of the narrowband display, ignore it, or get rid of it.

That's about all I can think of.....
Jay
Well - I've definitely got the correct wire (Connector #B135 Pin #17 right at the ECM.) What gauge wire should I be using?(any ideas).

And an excessive voltage drop would read 'lean'. As voltage increases to the 1v threshold from the sensor, the leaner the car is running. This the reason why when the circuit is open(ie unconnected), the gauge reads rich (0v).

I'm getting rid of it, but I'd still like to know whats going on with it... it should be half ass reading... which it's not even doing.

On a side note, has anyone used the Greddy E01 to monitor a wideband sensor?
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