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Fred
Moderator
Joined: Tue Jan 15, 2008 2:31 pm Posts: 15069 Location: Home sweet home!
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NB does NOT give you AFR....
_________________DIYEFI.org - where Open Source means Open Source, and Free means Freedom FreeEMS.org - the open source engine management system FreeEMS dev diary and its comments thread and my turbo truck!n00bs, do NOT PM or email tech questions! Use the forum! The ever growing list of FreeEMS success stories!
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Tue May 05, 2015 10:41 am |
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malcom2073
LQFP112 - Up with the play
Joined: Tue May 01, 2012 4:17 pm Posts: 211 Location: Shrewsbury PA
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Marek0086 wrote: I have some idea. Why would the output swing back and forth... rich and lean... if the AFR is constant?? AFR isn't constant. Narrow band sensors are very narrow band in the electronic sense of the term. They tell you if you're rich or if you're lean. Think a ball balanced on a knife, it'll fall one way or the other; very hard to keep it in the middle. The only way to use them is to vary the intended AFR by a percent and watch for it to swing high->low or low->high, then adjust as appropriate (Short term/long term fuel trims relate to this as to what adjustments over/under base are required to cause the swing). As Fred mentioned, it also makes Californians happy as modern catalytic converters are more efficient under an oscillating oxygen rich/learn environment, which was likely the primary push for narrowband use in this manner.
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Tue May 05, 2015 11:00 am |
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Marek0086
DIP8 - Involved
Joined: Fri Apr 24, 2015 5:26 pm Posts: 16
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Fine, Fred, let me rephrase that; if the AFR is CONSTANT at 14.7:1... why would the [sensor] OUTPUT also not be constant??
OEM narrowband output oscillates because the fueling is oscillating.
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Tue May 05, 2015 3:27 pm |
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Marek0086
DIP8 - Involved
Joined: Fri Apr 24, 2015 5:26 pm Posts: 16
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Fred wrote: NB does NOT give you AFR.... 14.7:1 is NOT an "AFR"?
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Tue May 05, 2015 3:33 pm |
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Fred
Moderator
Joined: Tue Jan 15, 2008 2:31 pm Posts: 15069 Location: Home sweet home!
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Marek0086 wrote: Fine, Fred, let me rephrase that; if the AFR is CONSTANT at 14.7:1... why would the [sensor] OUTPUT also not be constant??
OEM narrowband output oscillates because the fueling is oscillating. Mike carefully explained this to you above. Read his detailed explanation again. He's obviously got too much time on his hands, good for you.
_________________DIYEFI.org - where Open Source means Open Source, and Free means Freedom FreeEMS.org - the open source engine management system FreeEMS dev diary and its comments thread and my turbo truck!n00bs, do NOT PM or email tech questions! Use the forum! The ever growing list of FreeEMS success stories!
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Wed May 06, 2015 2:08 am |
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adamw
TO220 - Visibile
Joined: Wed May 14, 2014 10:04 am Posts: 14
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Marek0086 wrote: Fine, Fred, let me rephrase that; if the AFR is CONSTANT at 14.7:1... why would the [sensor] OUTPUT also not be constant?? OEM narrowband output oscillates because the fueling is oscillating. I would say if you had some very high accuracy combustion apparatus that could give you exhaust gas with a constant "lambda" held to with within about 3 decimal places and that lambda that you want to measure was somewhere between about 0.900 and 0.950 or 1.050 and 1.100 and the sensor temperature was kept constant to within about 20°C, then yes, your narrowband sensor would probably give a constant output voltage with reasonable accuracy. If any one of those variables are outside of the examples given above then you can only use a narrowband sensor as a "switch" - i.e on/off, rich/lean, 0/1... Redlines show where the curve slope is possibly useable:  [/url] **Later edited picture**
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Wed May 06, 2015 4:15 am |
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Fred
Moderator
Joined: Tue Jan 15, 2008 2:31 pm Posts: 15069 Location: Home sweet home!
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That's an optimistic graph that relies on the sensor being up to temperature, and varies, a lot, with temperature. Probably varies a lot between one an the next too. Also over a narrow Voltage range, so errors are large, etc.
He was specifying 14.7, at which point, no, no way, can you use it to hold stable. You could hold a stableish value away from that, but you couldn't say what value it was that you were using. The only way would be to reach steady state, then find stoich, and use math to find other AFRs assuming your calibrations were all perfect, or close to it.
_________________DIYEFI.org - where Open Source means Open Source, and Free means Freedom FreeEMS.org - the open source engine management system FreeEMS dev diary and its comments thread and my turbo truck!n00bs, do NOT PM or email tech questions! Use the forum! The ever growing list of FreeEMS success stories!
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Wed May 06, 2015 6:13 am |
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adamw
TO220 - Visibile
Joined: Wed May 14, 2014 10:04 am Posts: 14
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Fred wrote: That's an optimistic graph that relies on the sensor being up to temperature, and varies, a lot, with temperature. Probably varies a lot between one an the next too. Also over a narrow Voltage range, so errors are large, etc.
He was specifying 14.7, at which point, no, no way, can you use it to hold stable. You could hold a stableish value away from that, but you couldn't say what value it was that you were using. The only way would be to reach steady state, then find stoich, and use math to find other AFRs assuming your calibrations were all perfect, or close to it. Isn't that just saying what I said but in a different way?
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Wed May 06, 2015 6:35 am |
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Marek0086
DIP8 - Involved
Joined: Fri Apr 24, 2015 5:26 pm Posts: 16
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So a NB can be used as a "semi-wideband"??. Could you use a NB to read from 11.78 to 14.7 ??.
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Wed May 06, 2015 7:53 am |
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ivan141
LQFP112 - Up with the play
Joined: Sat Sep 29, 2012 9:16 pm Posts: 148 Location: Rotterdam, the Netherlands
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Multiple knowledgeable people just explained that no, you cannot. You're either very good at ignoring any information that doesnt suit you, or you're doing some expert level trolling.
If you're convinced that a narrow band can be used as a wideband, go out there, prove your point, amaze the world with your engineering prowess. All those evil companies selling us widebands all this time while we could have settled for marginally cheaper narrowband sensors, it's time someone put a stop to them. You go work out the details, I'll go put on my tinfoil hat and chant some mantras in support.
_________________ FABRICA MI DIEM, PVNC!
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Wed May 06, 2015 9:28 am |
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