akw408

I've been reading up, getting ready to use LS1 Edit for the first time. I've noticed alot of people seem to think they can tune their cars properly just using the stock O2 sensors. Well, I used to think that until I went to the dyno and autotapped while getting a real wideband O2 reading.

What I found was that the stock O2 sensors generally got the shape of the AF curve about right, but the range of the numbers could fluctuate quite a bit. I hear the O2 sensor can fluctuate depending on something as variable as temperature. Anyway, this is a link to my Excel spreadsheet showing the comparisons. This is 3 dyno runs.
http://home.attbi.com/~akwang408/akw408o2data.xls

Run 1 and 2 are consecutive, notice how big a change the range is. 0.98-0.96 in run 1 and 0.93 - 0.91 in run 2. I'm really only looking at the portion of the graph that shows to be around >12.5 AF on the wideband dyno. Run 3 occured about 5-10 minutes later, and even though I leaned it out a tad (you can see it in the wideband AF reading), it still read 0.94 - 0.93 on the autotap, what most people would perceive to be richer (and thus be incorrect).

Moral of the story is don't use the stock O2 sensors for fine tuning. I would just use it to see if I'm in the ballpark, but nothing more. If I had went and leaned my car out to the point where the O2 sensors read around 0.89 or so, I'm sure I'd be running too lean for comfort.



[Modified by akw408, 5:12 AM 8/9/2002]

Godspeed

They are good for the purpose of what GM put them in the car to do - tell the PCM how far away from the stoich 14.7 AFR's your engine is running. Asking them to tune your AFR at WOT to be perfect is to exceed the accuracy of there range of operation.

ChrisB

Good example, and I agree 100%!

TooManyIDs

Is this an issue with any automobile O2 sensor or is it specific to what GM put in the cars?

Godspeed

Honda has used true wide bands O2's in their cars before.



[Modified by Godspeed, 9:51 PM 8/23/2002]

vette.se

I posted about this a while ago ( http://forums.corvetteforum.com/zerothread?id=342011 ) and I got some info about a company ( http://www.egortech.com ) working with widebands and test equipment. They have a unit you can put in your car with two wideband sensors (replacing stock units). From the wideband signals it simulates the narrow-band stock sensors to the PCM giving the PCM a very accurate O2 reading. At the same time you can see the actual wide-band readings and A/F on the unit and even connect it to a computer for logging purposes.

I'm thinking of getting one to the next summer. We will se what happens :)


:cheers:

akw408

Yes, that is pretty much the point of the topic. Don't use the stock narrowband O2 sensors to tune your car to the ragged edge or you may regret it. :cheers:

evil-1

......... :yesnod: ..AMEN.. :yesnod: ..........

Big difference on the dyno, I want new sensors.. :mad

kewlbrz

There is also the consideration that the sniffing at the tailpipe with the wideband is seeing the catalyzed exhaust stream skewing the results somewhat.

The ultimate would be to place the Wideband in a bung before the cats for a truley accurate measurement. Also another consideration regarding dyno tuning, is that the load on the motor isnt what it is on the street.