02 voltage vs air/fuel ratio- finding a relible 02 4 your car

[ucancallmedebo]

I have asked this question in another thread but never got a response so I am trying here. My car seems to run around .82-.80 02 voltage at wot with zero knock at 15psi. I have a chip so my afc is zeroed out. At idle, increasing my low TH at 1k until stalling the car around +30 or more on the AFC the most 02 volts I can read with mmcd is .91. Judging from my 02 voltage at WOT .80-.82 with no knock, appox 90% of the max my bosch sensor will read is the ideal voltage for my car. I know there is a big variation from car to car but if I could get some input from other people such as max 02vtz at idle "full rich on this sensor"and 02vtz at WOT we could find out a more accurate formula for tuning without a wideband. By more accuate I mean,right now the standard seems to be .88-.91. This dosent fly for me and I now of others who run diffrent 02 volts at WOT with no knock. I am curious to see what the max 02 reading"full rich" of people running .91 at WOT is. If it was say .99 or 1.0 it would make sense that we are all shootin for about 90% of the max 02 reading as a baseling for tunning. With a couple of inputs we could find a average standard for the ratio of ( MAx Rich the sensor will read to 02 voltage at WOT with little to no knock). My ratio is 90%, what is yours. I am running 93oct. A higher octane gas would change the ratio of course,lets shoot for pump right now. Post your % and see how they stack up against other people.

 

[BoostedTalonTS]

Debo,
Your numbers are EXACTLY what I'm getting from my Bosch (#15730) O2 sensor... At WOT on my 94 with a comperably equipt set of mods, I get only .80-.82 volts with zero knock, but at 18-20psi of boost... I have tried different O2 manufacturers' O2 sensors before, but the ceramic kept breaking in them. -So far, the Bosch is the only one that will last longer than 4-6 months... I've tried Nippon Denso(OE), Borg Warner, AC Delco, and Bosch. So far, 2 boschs in the past 3 years (one got dropped and it broke durring an O2 housing swap).

I only get the CA "Diet" gas: 91 octane. With a reprogramed EPROM chip, and with my SAFC set to add fuel at anything above 5600 rpm, in my tallest gear, I usually see O2s around .88 -.90 volts above 5600 RPM, but at that point, I'm REALLY moving and I usually don't go that fast around this cop-rich environment

Hope this helps (and I thought that I was the only one running "low" O2 sensor voltages)


..On a side note, I was able to richen things slightly by adjusting the 2G MAS's block-off screw in the lower center passage. -I had previously blocked-off this passage entilely when I was running 510cc injectors but now, with the 560cc set, I just tightened that black plastic scew a few turns to add about .02 volts to the totals listed above. -You might want to try this out for yourself.

 

[ucancallmedebo]

Moving the safc up a couple of points across the board would have the same affect right? Even at +10 across my 02voltage never really goes any higher than .82 at WOT but I can feel the powere loss from running to rich. You have the same problem but can get .88-.91 in high gear. Maybe the longer run in high gear gives the 02 a chance to clean out and gives a more relible reading. I have not tried logging a 110+mph long 5th gear run yet as I am still waiting on a afpr "1 month now" so I am trying not to drive the car.I am curious as to what the highest your 02 will read "full rich"since u have about the same prob as me.

 

[LandoAWD]

Narrowband O2s are not to be tuned by. Tune by timing advance, knock, IPW, etc.

 

[ucancallmedebo]

I know but they do give some indication of lean/rich. And from what the average person will tell me with a .82 02 is I am lean and that is just not the case for my car. In my case I have problems with rich knock and for the longest time I thought I was lean and kept richening it up to no end. Creating more knock, and higher EGT's. If a formula like shooting for 90% of a cars max 02 would put me in the ballpark for what I am shooting for at WOT then It would have been easier than trail and error, checking plugs. ect. I am not trying to argue with you but only tunning with timing advance, knock, IPW lead me to beleive I had phantom knock for the longest time. Logging my car with .85 dropping to .82-.80 at 5krpmthe .85 was so rich it was causing the knock for me. I am just looking at all the variables thats all.

 

[90AWDTalon]

Narrow band o2's are worthless for tunning. I recently got a wide band, prior to installation with an after market narrowband o2 I was getting .8 - .82 volts at WOT, most people would say at these voltage's your extremely lean, but this seemed to work well. I made no changes other than installing the wideband. I was at 10.4:1 air fuel ratio, very very rich I had to lean things out an additional 16% to get to where I'm at now, 11.5:1.

Because of the low o2 readings, I thought there was no way I could safely lean things out any more. Turns out I was wrong.

I am in no way telling people to lean things out if they are getting .8 volts, I'm just sharing an experience illustrating narrowband o2's worthlessness for tuning.

 

[BoostedTalonTS]

Moving the safc up a couple of points across the board would have the same affect right? Even at +10 across my 02voltage never really goes any higher than .82 at WOT but I can feel the powere loss from running to rich. You have the same problem but can get .88-.91 in high gear. Maybe the longer run in high gear gives the 02 a chance to clean out and gives a more relible reading. I have not tried logging a 110+mph long 5th gear run yet as I am still waiting on a afpr "1 month now" so I am trying not to drive the car.I am curious as to what the highest your 02 will read "full rich"since u have about the same prob as me.

I guess, at first, adjusting the SAFC would have the same effect... However, I don't think that the ECU will add more timing to the mix if it's done that way, as you are leaning out the unmetered section of the MAS, vs the SAFC way of changing what the ECU "sees", from the metered section of the 2G MAS.

After more logging, I found that I can't get richer than .89 now (thanks to the MMCD 1.6n's peak/hold feature). -Possibly because of the nicer weather lately? -Nothing else has been changed recently.


As for the standpoint of using the O2 values to tune with, I agree that it shouldn't be a major factor in making "course" adjustments, but after the initial tuning (as memtioned in previous posts, with RPM, TPS, TIMA, IPW, ect, ect...) has been done, it might provide some insight to eliminating knock and alow for more "finer" tunning.

Hey 90,
What type of WBO2 did you go with, and (more importantly) how much did it set you back $$$ ? How long is the O2 sensor good for? -Correct me if I'm wrong, but I thought that WBO2 sensors, although more accurate then the narrow band sensors, don't last as long.

 

[90AWDTalon]

Hey 90,
What type of WBO2 did you go with, and (more importantly) how much did it set you back $$$ ? How long is the O2 sensor good for? -Correct me if I'm wrong, but I thought that WBO2 sensors, although more accurate then the narrow band sensors, don't last as long.

I got the PLX M-300, about $325 shipped from horsepower freaks. The PLX systems is designed to be permanately installed so it has built in soft start, which should prolong its life. There are a few oem applications that use the same sensor as there kits, so they are capable of lasting a while. I just hope mine does, I made the mistake of ignoring the directions when they said to install atleast 24" from the turbo. I installed it in the stock location, for the first week or so I didn't go for any lengthy drives and it worked perfectly, but after about a 30 mile drive it overheated and quit working. After letting the car sit for a while it started working again. I ended up plugging the stock location and getting a new bung installed farther down the down pipe and haven't had any issue's since.

You can't even compare the accuracy between narrowband ane wideband. Narrowband units are only accurate at stoich 14.7:1.

Narrowband accuracy

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Wideband accuracy

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[ucancallmedebo]

Thanks for posting those charts. That narrowband is really a peice of crap huh. By the looks of the chart there the wideband is at least 10 times more accurate and probally more. Well I feel I need to get serious about tunning so I am gonna get a wideband. I have a logger but with the PLX is there anyway but looking at the AF/R, as far as logging it without a laptop, or am I restricted to realtime. Does it log anything on its own or would that require more equipment.

 

[90AWDTalon]

I have a logger but with the PLX is there anyway but looking at the AF/R, as far as logging it without a laptop, or am I restricted to realtime. Does it log anything on its own or would that require more equipment.

The PLX M-300 has an analog wideband output that can be logged in a few different ways. Some of there more expensive units have better logging capabilities. My car has a federal ECU, so I don't have an EGR temp sensor. I connected the wideband output to this pin and then with MMCD I use a custom sensor to log that address in the ecu, I think it was 12 but this should be looked up to make sure. The output is raw so you need to take that value and multiply by 0.0196 to convert to volts and then you can use the formula A/F = volts * 2 + 10. Only problem with this is there seems to be an issue with the logged values of any wideband, not just PLX, of the logged values not matching the displayed value. You can create a correction factor to make them match. For me subtracting 0.3 from the logged A/F ratio seems to work pretty good, but you'll have to figure out what works best for your car.

Here's PLX's website, they have lots of good info, thats were I got those graphs from.
http://www.plxdevices.com/index.htm

EDIT:
Heres another popular wideband, about the same price of PLX.
http://www.innovatemotorsports.com/products/lm1.php