02 help

[denn454]

i made my own o2 reader today, few pieces of wire and a multimeter. its cheap, looks like some redneck hillbilly thing to do, but its a lot better than nothing.

anyways i can't make sence of the numbers.

idle is anywhere from 520 down to 450
cruise is in the 600's depending on the speed and rpm...
full throttle really confuses the hell out of me. when i hit it i jump up to 890 or so, it stays there till about 60mph then drops down. at about 80mph ts running about 815mv

I know mid 800's are the number to look for but when do you want to see that number?

 

[BoostKillsStres]

The numbers don't mean anything unless your at WOT or running an open loop chip. The stock o2 at non WOT is constantly switching back and forth across about 400 to 440mv depending on which scan tool your suing trying to achieve a ~14.8:1 air fuel ratio so as long as you have a decent amount of o2 cross counts thats about all you care about.

 

[denn454]

sorry, i'm completely new to this, what are or how do you get cross counts?

and is there any one point where i should take the numbers at, and tune accordingly?

 

[denn454]

ok, at the track i was getting right at 820 crossing the finish line. that sounds a bit rich to me, but its lower at lower rpm's. should i just lean it down a bit and call it good?

 

[BoostKillsStres]

Well, as long as you weren't seeing knock you could lean it down a little or run more boost and see if the MPH picks up since thats the true signal your making more power. Just watch that knock and tune for highest MPH.

 

[ijames]

In normal closed loop operation the ecm is constantly alternating between rich and lean, so that it averages stoichiometric, to keep the catalytic converter happy. Each time the afr swings from rich to lean, or lean to rich, is a cross count (it crosses stoich). At WOT the ecm stops doing that and richens things up considerably, based on several PE tables in the chip (power enrichment mode). You are reading the O2 sensor directly with a voltmeter, but due to an unfortunate historical accident the O2 readings reported by TurboLink and DirectScan are incorrect. Yours will correspond to what users who have an OTC4000E would see, and should be higher. With TL or DS, people tune for the upper 700's (or maybe low 800's with pump gas) at wot in 3rd gear, while your target will be more like 920-940 mV (do some archive searches to find some examples that others have posted since I'm working from memory and do not have an OTC4000). If you tune for the upper 700 mV range with a voltmeter you will be seriously lean.

 

[denn454]

ok, i was thinking it was a little on the lean side and was leary of leaning it out a little more. thats good to know that i can ritchen it up a bit.

i always run a little higher octane at the track then i would actually need to prevent any detonation. I do like the idea of tuning hor high mph. i'll give that a shot when i can make it up to the track. hopefully the weather will coperate soon.

just one other thing, in that cross count (thatks for the explination!) is there any range i want to have (say between 100 and 200 or 100 and 300 i'm just pulling those numbers our of nowhere) or is the idea to keep those numbers between a certain range. i dont' think waht i said makes sence. do i want a distance between the high and lows, or do i want the high and lows to be in a certain area?

thanks for your help!

 

[BoostKillsStres]

There is no cross count "setting" your looking for, its simply a counter that runs from 0 to 255 then resets to 0 and counts up again. You just want to see a decent amount of counts per frame for whatever logging device your using to know that the O2 sensor is very actively switching across the stoich point around 14.8:1 Air fuel.

 

[ijames]

With an aldl scan tool like TurboLink you should see 5-10 cross counts per frame (every 1.4 seconds), and cruising at 65 mph maye 35-50 cross counts per frame. That indicates the O2 sensor is "active" and the ecm is happy . You also want to see the O2 volts get over 750 mV and under 150 mV pretty often as it swings up and down. When a sensor gets lead fouled it will get "lazy" (slow to respond so the cross counts drop off) and will lose range, only going up to 650 or 700 mV and down to 200 or so. These voltages are all as read by TL, not your voltmeter. You really need to borrow a scan tool and rig up a potentiometer to inject your own "O2 signal" into the O2 sensor input line so you can see a stable signal with both the scan tool and your voltmeter, to get a solid answer on converting the tuning values you see here to your voltmeter. You want to feed 0-1 V, so something like a 10 K pot with one end grounded, the wiper to the O2 connector and your meter with sensor unplugged, and a 100 K resistor from the other end of the pot to the 12 V battery. Start with the pot in the middle of its range for about .5 V, key on engine not running, and compare the scan tool and your meter. Then check every .1 V or so from .1 to 1 V, plot the data, and you should get a nice straight line that you can fit and use from now on.

One way to tune is to slowly add fuel while watching your 1/4 mile mph and go until the mph drops off a little and then back up one step.

 

[denn454]

THANK YOU!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

thats not as tough as i thought it would be. i'll be getting a turbo link soon (already have the laptop, just need more dinero) i'll see what i can do with the poteometer, i understand exactly what your saying to do. but from what i've seen compared to what you described i should be right on, just a little on the lean side. it does like to jump up and down just like you said.

THANKS!

 

[tttype]

crosscounts

While trying to figure out a high BLM problem I unhooked the O2 sensor & still got 200 crosscounts in a frame after that ?

 

[denn454]

if the o2 isn't connected, then there is no way you should be getting anything from it... that just doesnt' make sence.

and what are blm's?