AFR Tech Question

General engine tech -- Drag Racing to Circle Track

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user-23911

Re: AFR Tech Question

Post by user-23911 »

racear2865 wrote: Thu Jul 05, 2018 10:12 am

OK, been running my dyno since 1975 and lets dispel some myths. Making no changes but changing carbs and going from one droplets size to another and setting up for AFR, you may find that large droplets dont always completely burn and a fully atomized system will burn more fully.
reed
When you run a proper 5 gas exhaust analyser on the dyno, you'll know this because the CO, HC, O2 levels will change.
An incomplete burn is a dirty burn and higher in emissions.
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Re: AFR Tech Question

Post by gruntguru »

joe 90 wrote: Thu Jul 05, 2018 3:34 am At lambda 1 the pump cell changes polarity so there's no straight line to try to extrapolate.
Not at all. The slope is determined by the ratio of ion diffusion rate to voltage driving the pumping cell. Polarity reversal simply means the oxygen ions are being driven in the opposite direction, the reversal won't affect the ratio.
user-23911

Re: AFR Tech Question

Post by user-23911 »

It's pump current that's measured whilst trying to maintain a set voltage in the cell.

The current can flow either way and it's not linear with respect to AFR, it's the controller circuitry which tries to make it linear.
user-23911

Re: AFR Tech Question

Post by user-23911 »

Straight from Bosch.

http://photobucket.com/gallery/user/arg ... anBn/?ref=


So from that and knowing it's naturally calibrated at lambda 1 and also at the lean end in free air, would you trust the reading at the 0.7 lambda end of the scale if you can't check it against something else?


On the subject of droplet size, there's a lot of documented info on large upgraded injectors which don't atomise the fuel correctly giving a dirty burn with a lot of soot and also down on power.
The WB sensor might say the AFR is correct (too lean to make soot) but other instruments will say it's not correct.
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Re: AFR Tech Question

Post by Paul Rig »

wouldn't the answer be fuel atomisation.
Measured by AFR wideband cross referenced by exhaust temps of each cylinder?
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Re: AFR Tech Question

Post by Warp Speed »

It's funny, EVERY time there is a tuning thread, Joe turns it into a "how an O2 sensor works", and "how bad a wide band sensor is" thread! LOL #-o
user-30257

Re: AFR Tech Question

Post by user-30257 »

Warp Speed wrote: Fri Jul 06, 2018 7:40 am It's funny, EVERY time there is a tuning thread, Joe turns it into a "how an O2 sensor works", and "how bad a wide band sensor is" thread! LOL #-o
Yeah, they are so bad that OEM's have to use them.
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Re: AFR Tech Question

Post by cab0154 »

racear2865 wrote: Thu Jul 05, 2018 10:12 am
cab0154 wrote: Fri Jun 29, 2018 1:52 am Not sure why anyone would target a given AFR. Its just a number. If you went from a junk carb to a carb with great emulsion and atomization you could theoretically get the same AF from both with the great carb using less fuel volume but making more power; due to far greater combustable surface area of the mixture.
OK, been running my dyno since 1975 and lets dispel some myths. Making no changes but changing carbs and going from one droplets size to another and setting up for AFR, you may find that large droplets dont always completely burn and a fully atomized system will burn more fully.
reed
That would explain why a lot of the newer nitrous stuff with better atomization are running leaner A/Fs and not burning anything up.
"Anyone who thinks the low RPM engine will be faster just does not have as much experience as the rest of us" -The late, great Joe Sherman.
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Re: AFR Tech Question

Post by Tuner »

Warp Speed wrote: Fri Jul 06, 2018 7:40 am It's funny, EVERY time there is a tuning thread, Joe turns it into a "how an O2 sensor works", and "how bad a wide band sensor is" thread! LOL #-o
He has an internal feedback loop with a veeeerrrrrry narrrrooooowoowoowoowoo band sensor and probably hasn't read this https://www.sae.org/publications/techni ... 9-01-1680/
or this https://patents.google.com/patent/WO2008154366A2/en :wink:
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