Do these A/F ratio gauges actually give a correct reading?
02-23-2004, 08:17 PM
#12
Originally posted by marcucci
The Autometer and other "narrowband" gauges are very accurate- for what a narrowband measures. What people mistake a "liteshow" for is actually proper operation. The narrowband oscillates back and forth around rich/lean which is all they indicate. For THAT, they are very good. This is all most people need- an indication that the fuel system is functioning normally. Most fuel system failures are pretty catastrophic and result in a very lean condition- not a slight change. Assuming proper tuning with a wideband, a narrowband gauge acts as a good safety/warning device.
The Autometer and other "narrowband" gauges are very accurate- for what a narrowband measures. What people mistake a "liteshow" for is actually proper operation. The narrowband oscillates back and forth around rich/lean which is all they indicate. For THAT, they are very good. This is all most people need- an indication that the fuel system is functioning normally. Most fuel system failures are pretty catastrophic and result in a very lean condition- not a slight change. Assuming proper tuning with a wideband, a narrowband gauge acts as a good safety/warning device.
I believe that it is showing what it needs to show. For example, after a cold start, while it's warming up, it's showing RICH and that's the way it should be.
On the one hand, I've got a light show but then, does a wide band guage show numbers that zip up and down and is un-readable?
02-23-2004, 08:41 PM
#13
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I have a 10 LED display (homebrew) hooked to the 0 to 1 volt output of my AEM wideband (the 0 to 5 volt output goes to the ECU for O2 feedback). The display does not "zip up and down"; it sits, quite stably at the AFR that the engine is controlled to by the ECU. For my car, that's about 13.5 at idle with 14.5 at cruise, rising to 13 at full throttle -- normally aspirated. My Miata, on the other hand, has a factory ECU and when I use the display on it, the signal does "zip up and down." I think (don't know for sure) that the difference is due to the different feedback approaches used by the two ECUs -- and also by the nature of the two O2 sensors.
The stock O2 sensor in the Miata (as in the S2000) has a curve of voltage vs. O2 concentration that is so steep that it is virtually a digital device. And it seems that the ECU does a limit cycle control while in idle and light throttle. That give the zippy display. On full throttle, the ECU goes open loop, giving the fuel dictated by the map, and the display is rather steady -- and, hopefully, rich.
On my S2000 engine, the output of the AEM wideband sensor is smoothly linear with varying O2 concentration. And the AEM ECU uses more traditional feedback, settling on a steady fuel level for any set of input (rpm & load) conditions. So the O2 level is stable and the display is stable.
The stock O2 sensor in the Miata (as in the S2000) has a curve of voltage vs. O2 concentration that is so steep that it is virtually a digital device. And it seems that the ECU does a limit cycle control while in idle and light throttle. That give the zippy display. On full throttle, the ECU goes open loop, giving the fuel dictated by the map, and the display is rather steady -- and, hopefully, rich.
On my S2000 engine, the output of the AEM wideband sensor is smoothly linear with varying O2 concentration. And the AEM ECU uses more traditional feedback, settling on a steady fuel level for any set of input (rpm & load) conditions. So the O2 level is stable and the display is stable.
02-24-2004, 12:52 PM
#17
THANK YOU! I've always been of this opinion but have been reluctant to say so because I didn't quite know how to put it. You said it for me. I have one of those "light show" Autometer guages and it's suits me fine for what I want to know. All I care about is that at WOT, under heavy boost, I'm in the green (rich) and NOT in the red (lean). The "Christmas tree" effect is no big deal when I'm idling or at steady state running.
(By the way it runs richer with the silencers in).
02-24-2004, 07:15 PM
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Originally posted by beroznikmal
mase1, I am curious as to how you conducted these tests? wehat is the magnitude of " abit off"? if it 1 or less than 1??
Thanks
Beroz
mase1, I am curious as to how you conducted these tests? wehat is the magnitude of " abit off"? if it 1 or less than 1??
Thanks
Beroz
we took a test vehicle. that had two o2 bungs. kept all things the same (ie coolant and intake temps) and only changed out the different widebands and did some wot pulls
We kept the dyno wideband in, and in the other was the portable widebands.
the plx was off by .04:1-.06:1 and it wasnt a linear error either.
typically the other widebands were off at most by 0.0:0 - 0.3:1
02-24-2004, 09:27 PM
#19
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http://wbo2.com/
Originally posted by beroznikmal
let me see what I can do ... do you have a link to their Webpage?
let me see what I can do ... do you have a link to their Webpage?