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post #1 of 3 (permalink) Old 01-30-2009, 10:09 AM Thread Starter
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Hi,
I was doing some more research, this time i'm looking to get an a/f gage, and came across something that confused me. Hopefully someone here can clarify this for me.

Here is the linkAEM's Installation manual
Within this manual, at the bottom of the second paragraph, is a sentence that says:
"These sensors were designed for operating closed loop around the stoichiometric AFR (14.64 for gasoline), and for performance tuning they are useless."
The part that caught my attention is the, "...for performance tuning they are useless."

I dont understand what their use is then. Can anyone explain what this sentence is saying that might make me think that purchasing this product has a useful purpose?

The reason i ask is because in my recent search for information regarding gages, a UTEC, and general tuning info, i remember reading accounts of people tuning on the street by datalogging and by just shouting out RPM increments and having a partner write what the a/f gage says at that time. This seems to have been a waste of time for these people after having read this manual. Then again i dont actually understand what this manual is saying in this instance so i could be wrong entirely.

Could someone please explain this to a layman?

Thanks, BTW i have another acronym for that list...Universal Exhaust Gas Oxygen (UEGO) sensor
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post #2 of 3 (permalink) Old 01-30-2009, 12:14 PM
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QUOTE (OhhdangZ @ Jan 30 2009, 08:09 AM)
Quote:
Hi,
I was doing some more research, this time i'm looking to get an a/f gage, and came across something that confused me. Hopefully someone here can clarify this for me.

Here is the linkAEM's Installation manual
Within this manual, at the bottom of the second paragraph, is a sentence that says:
"These sensors were designed for operating closed loop around the stoichiometric AFR (14.64 for gasoline), and for performance tuning they are useless."
The part that caught my attention is the, "...for performance tuning they are useless."

I dont understand what their use is then. Can anyone explain what this sentence is saying that might make me think that purchasing this product has a useful purpose?

The reason i ask is because in my recent search for information regarding gages, a UTEC, and general tuning info, i remember reading accounts of people tuning on the street by datalogging and by just shouting out RPM increments and having a partner write what the a/f gage says at that time. This seems to have been a waste of time for these people after having read this manual. Then again i dont actually understand what this manual is saying in this instance so i could be wrong entirely.

Could someone please explain this to a layman?

Thanks, BTW i have another acronym for that list...Universal Exhaust Gas Oxygen (UEGO) sensor
The paragraph you quote is talking about narrow band sensors. With a narrow band sensor, the slope of the output voltage versus air-fuel ratio is very steep around 14.6:1, and much flatter as you move away from this ratio. In essence, these sensors are switches. They indicate when you are running rich or lean, but don't tell you how much rich or lean. Narrow band sensors are installed in the exhaust system before the catalytic converter to signal the ECU to adjust the air-fuel ratio. If the sensor says "lean," the ECU will increase fuel delivery in small steps until the sensor says "rich," then decrease the fuel delivery in the same small stems until the sensor says "lean" again, and continually repeat this cycle.

Wide band sensors, like the AEM UEGO, have a shallower voltage versus air-fuel ratio slope over a wider band of air-fuel ratios. They can be used to tune the engine to a desired ratio as long as that ratio is in the sensor's bandwidth. Wide band sensors are also installed after the catalytic converter and are used by the ECU to determine how well the cat is working. The 350Z uses narrow and wide band sensors as described above. Your AEM meter uses an additional wide band sensor, since splicing into the Nissan sensor will probable change its output voltage and throw off the ECU.

Karl
2005 Enthusiast 6MT
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post #3 of 3 (permalink) Old 01-30-2009, 01:03 PM Thread Starter
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Awww...i see now. The paragraph before that one starts describing the narrowband and its limited funtionality and that paragraph was still describing it. Whoops. I just read it wrong...please disregard this brain fart of mine.

Thanks for enlightening me.

We can probably close this thread...
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