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Old 09-18-2012, 12:01 AM   #1 (permalink)
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SGII AFR is static

hi guys i have programmed my SGII to display some extra gauges like AFR, absolute load, o2 sensor temp, o2 voltage, maf, etc...

my problem is with the A/F sensor. it is very boring to monitor because it seems to be always at 14.5-14.7 range. unless i climb past 3.5k rpm at wot i don't see much difference. at 6k rpm in wot i have seen it hit 10.9. otherwise its fairly static including wot at 2500rpm in overdrive gear. you guys with wideband sensors, is this correct? is your afr always at 14s unless your operating at high engine speeds no matter what?

thanks
Ali

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Old 09-18-2012, 09:21 AM   #2 (permalink)
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Yeah, that is how it should be. Not to mention that a stardard O2 sensor can't measure much outside the range of 14:1 - 15:1. So, that 10:1 you got is probably horribly inaccurate.
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Old 09-18-2012, 01:39 PM   #3 (permalink)
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That is NORMAL "closed-loop" operation.

During "closed-loop" operation, the computer constantly adjusts fuel quantity so as to MAINTAIN a perfect "stoichiometric" 14.7:1 A/F, and only allows the engine to go richer when almost wide-open throttle (WOT) input from the driver is detected (plus a few 'other' unique situations).

Part of the *reason* for this 'stoich' operation is the catalytic converter(s) need something to "burn" and this 14:7 A/F-ratio provides that minute amount of gasoline. The "lean best burn" A/F-ratio for maximum fuel economy is something like 16-18:1 A/F-ratio, so obviously today's engines are NOT getting anywhere near the FE that the older (pre-EPA) engines could, and nowhere what they COULD get if EPA regulations weren't so obsurd.

In fact, the Honda HFE engines, which routinely operated in this "lean-burn" region (16-18 or more A/F) to achieve excellent FE are nolonger permitted because of their NOx emissions while in "lean-burn."

Last edited by gone-ot; 09-18-2012 at 01:47 PM..
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Old 09-19-2012, 12:05 AM   #4 (permalink)
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ok so the my gauge is working properly. in closed loop under 3k rpm almost always in the 14s. at cold start in open loop and at operations over 3k rpm with wot it dips to 13s. lowest i have seen is 11:1 at 6000rpm wot. highest 20:1 while coasting downhill. 90% of thr time though its 14.5. pretty useless since i barely go over 3k rpm or go wot.
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Old 09-19-2012, 12:34 AM   #5 (permalink)
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That's actually pretty interesting, I think a lot of cars run closed loop at high load low rpm, but they have wideband sensors and definitely enrich the mix. Never heard of no enrichment at WOT...
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Old 09-19-2012, 04:18 PM   #6 (permalink)
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Quote:
Originally Posted by serialk11r View Post
That's actually pretty interesting, I think a lot of cars run closed loop at high load low rpm, but they have wideband sensors and definitely enrich the mix. Never heard of no enrichment at WOT...
correct my car stays in closed loop under 4000rpm at wot. however a/f enriches already at 3500rpm with lots of throttle. low rpms (below 3k) are almost always in the 14s from what i have seen no matter how much throttle/load. only time i have seen it run rich below 3k is during cold starts at about 13.5-13.8. during these cold starts my fuel flow rate is 1.3 gallons per hour. this condition at cold start is giving me a major headache because it ruins my overall mileage.

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