Guest ZmeFly Posted March 20, 2004 Share Posted March 20, 2004 Is it true that you can get a decent reading of whay you a/f may be buy hooking into the O2 sensor via a multimeter? If so does anyone know how to do this and how I would go about doing this on my car. Id like to do some adjustments but dont have the cash for a dyno, just something to get me in the ball park if anyone has any other ideas please let me know. Thanks, James Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted March 20, 2004 Share Posted March 20, 2004 You can measure the output of the O2 sensor using a digital multimeter (set on volts). An analog type has too little input impedance and will not make an accurate measurement. 0V = lean about 0.5V = stoich >0.8V = rich Ands that's as accurate as the O2 sensor gets. Quote Link to comment Share on other sites More sharing options...
Guest ZmeFly Posted March 20, 2004 Share Posted March 20, 2004 Thanks a lot Sleeper, that will at least get me in somewhat a decent area. I do have a digital as I agree the analogs arent worth DO DO. Thanks again, James Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted March 20, 2004 Share Posted March 20, 2004 It will work the exact same as if you hooked up any of the aftermarket A/F gauges... that's all those gauges do is take the voltage reading and light up an LED. But how are you planning on using a multimeter to measure A/F ratio under load while driving? Quote Link to comment Share on other sites More sharing options...
Guest ZmeFly Posted March 21, 2004 Share Posted March 21, 2004 I have enough wire on mine to do that right in the cockpit. Its nice to know what ratio you are at and what the gauge is reading as well. Just taped that sum bitch to the horn pad with some good ole duck tape and off I went. I found this on one site though the guy does mention not to take it as gospel, but a good starting point and out refernce. Note that the voltages from the O2 sensor are very low, so take extra care in taping the signal wire and make a high quality connection. This is whatI gathered for my Intellitronix gauge. The table represent what the lights signify. Please keep in mind that this is for the non modifed gauges and in the the measurements are in the wider resolution mode. This should be pretty close, but don't hold me to these values. LED 10 - 0.97V - 12.1:1 - Very Rich - Forced induction and nitrous. you might want to be around here. LED 9 - 0.88V - 12.7:1 LED 8 - 0.78V - 13.2:1 LED 7 - 0.69V - 13.8:1 LED 6 - 0.59V - 14.4:1 LED 5 - 0.49V - 14.9:1 - (Stoich- pretty close to 15:1, this is where NA motors should be at) LED 4 - 0.39V - 15.4:1 LED 3 - 0.30V - 16.0:1 LED 2 - 0.20V - 16.5:1 LED 1 - 0.10V - 17.1:1 - Lean If this table truely has any merit, Im running quite well at idle Im at .71, at boost im between .80-.91 but as most said and through the O2 and multimeter I read this at about 5k im leaning out to .69 which according to the above chart is around 13.8:1 Thats not good. Is this the bane of all stock ZXT's, what does cause this?? Ive read a lot and well I have most all the upgrades that were mentioned, ie, bigger better fuel pump, no longer have an AFPR, but a new one, all vacumns are in good shape, what gives, is it just the not so great design of the ECCS? Hmm I hope when I go to the Z31 setup things will change. Quote Link to comment Share on other sites More sharing options...
tec280zx Posted March 21, 2004 Share Posted March 21, 2004 I thought the o2 sensor only worked under part throttle.... I don't think it would accurate to read its out put under full throttle Maybe i'm wrong though...someone school me.... Quote Link to comment Share on other sites More sharing options...
Guest ZmeFly Posted March 21, 2004 Share Posted March 21, 2004 Well after a little tuning with the AFM Ive come to better consistent readings, yet Im sure they will change as with the weather and what not. Just a little fine tuning of the AFM though netted me a .87 at 5500 rpms. Now if the O2 sensor is giving me correct readings, and well this chart so to speak is somewhat accurate, then I should be around 12.8-13.0:1. Still not great but a lot better then what my first readings were. Can anyone withmore experience elaborate on this? James Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted March 22, 2004 Share Posted March 22, 2004 ZmeFly - Don't try to calibrate that voltage curve. It will vary from O2 sensor to O2 sensor, and it will vary with temperature as well. If you have ever seen a graph of the voltage vs. mixture, it is not even CLOSE to linear. Seriously, anywhere richer than 13:1 can read from 0.7V to 1V, and anything leaner than stoich will be close to zero. There is a reason for the price and popularity of wideband O2 gauges. Quote Link to comment Share on other sites More sharing options...
Guest ZmeFly Posted March 22, 2004 Share Posted March 22, 2004 Now doesnt that suck Well I was thinking I was doing something good. Bummer, and yea I figured it wasnt that accurate, but if I could at least get something out of it it might do me just a little bit better. Ill have to wait till Im rich one tax season and single lol Thanks for the heads up Sleeper. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 22, 2004 Share Posted March 22, 2004 Just to be devil's advocate here, a buddy of mine spent 5 hours on the dyno yesterday. He dialed in his a/f ratio, and the guy doing it was making fun of his single wire O2 sensor a/f gauge. Turns out the gauge was dead nuts accurate. Jon Quote Link to comment Share on other sites More sharing options...
80LS1T Posted March 22, 2004 Share Posted March 22, 2004 I just installed an Autometer A/F ration gauge in my dash but I installed it mostly because I needed a gauge to take up a spot! It would have looked funny if I didnt have a gauge where it is now! See what I mean! I couldnt have just left that spot empty! I dont plan on using the gauge as an accurate reading due to the fact that the O2's are not wideband. However I have the gauge hooked up so that I can read either O2 with the flip of a toggle switch. So atleast I will be able to tell if the 2 banks are running close to each other. Thats all I am hoping for anyways! Quote Link to comment Share on other sites More sharing options...
Guest ZmeFly Posted March 22, 2004 Share Posted March 22, 2004 Well as far as the A/F gauge that I have, its an autometer unit as well, its reading right on with the multimeter readings, which is something that I also wanted to see. Its not that I doubted how well it was reading just that I wanted to know what those readings were at what level with the O2 and see about where I was at with the A/F ratio. Hopefully sometime in the future I can invest in one for more percise measurements. 80 LT1 that instrument cluster looks really nice, and I do see your point, would have looked like arse without a gauge there. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted March 22, 2004 Share Posted March 22, 2004 And I'm not saying the gauges are completely useless, I have one myself, and it seems to be consistent as well. I've just seen enough data to know they cannot be relied upon as a precision instrument. The fact that it is an oxygen sensor implies it cannot reliably measure degrees of richness because there is close to zero oxygen in any "rich" mixture. The wideband "oxygen" sensors use a different technology, and do not simply measure an oxygen level. Quote Link to comment Share on other sites More sharing options...
Guest Peyman88zxt Posted March 22, 2004 Share Posted March 22, 2004 Narrowbands are fine if you are trying to tune around stoich. Once you start trying to adjust you a/f mixture around 11-12 you run into problems. Its true that if you find the response plot of the narrowband you'll be able to see where you are at. But on a narrowband the difference between 9 and 11 is only about 50 milivolts. Those sensors vary in output that much just by varying temperatures or your battery voltage. Basically They don't have enough accuracy to be able to base your af mixture on 50 millivolts difference. I tried doing that for a few months and was able to get it to a point were it was drivable and I could boost well. But when installed the wideband, it showed that I was close to 9afr under high boost, which is way too rich. After a couple of hours with the wideband, I got more accomplished than I did 5-6 months with the narrowband. Quote Link to comment Share on other sites More sharing options...
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