Are O2 MV's supposed to stay steady in 3rd gear at WOT??

[Dr. Jeckel]

I have posted this a couple times awhile back and have received different answers and still am not sure what is true.
If you are doing a WOT run, should the O2 mv's settle when you get to 3rd gear during a WOT run? I know that 780mv is the target to shoot for.
My car's O2 readings never settle. If I do a WOT run starting in 3rd gear at about 70mph my O2's read around 840-850mv's when i floor it, as my speed increases in 3rd my O2's slowly drop by about 10mv's a frame. I stay in the gas until the readings get to 770, then I get of the gas(still in 3rd, probably around 5300-5400rpm I'm guessing by the factory gauge). I usually have little to no KR at 14-15psi in 3rd gear even with the O2's dropping.
My question is this: How can you tune for 780mv's in 3rd if they don't stay steady?
My turbo seals are going bad and leaks oil into the intake. I am replacing it with a TA60 maybe this weekend. Could oil leaking into the intake charge be causing me to get leaner on the top end?
I have also tried to denso sensors with the same results and have gone back to my AC Delco unit. CC's are good and very active so a bad sensor is ruled out.
I would like to hear what everbody elses O2 readings do on their WOT runs. Do your O2 readings settle and stay at or around a certain number in 3rd?
Maybe I'm to dense to understand but please help me in clarifying this subject.
Thanks, James

 

[turbot2112]

youre shooting for 780s, probably safer at 820s on pump gas. that is the reading you want towards the end of your pass. they will start high and go down the faster you go.

 

[XLR8]

My O2s drop slowly throughout 3rd gear so I tune so that my target O2 is at the end of the track. That is if I am shooting for 780 I will want 780 as I cross the end of the 1/4 mile.

 

[Snorman]

As the others said, they'll drop.
The car is encountering increased resistance as it accelerates through 3rd gear, loading the engine more the faster you go.
FWIW, I always monitor my O2's on a full pass. I never like going WOT from a roll. I feel that I can watch them more progressively and get a better idea of where they are.
In any case, O2's aren't even the best way to tune. I'll be running an EGT when I change my combo in the spring.
S.

 

[Lee Thompson]

02 volts

If your chip is RIGHT, yes, your 02 volts will stay constant within a range all the way through a run. Red Armstromg was kind enough to work with me at BG a couple years back and now my 02 volts stay between 810 and 790 for the 1/4 mile. Hope this answers your ? And no they do not start at 810 and drop to 790.

 

[Dr. Jeckel]

This is what I am talking about. Within this post are differing ideas of what the O2 readings should be doing during a run. I realize they are not the best to tune by, but i want to figure out what they should be doing, so I know if something else if off.
How do other people read O2's as being correct?

 

[strikeeagle]

I don't see any "differing ideas" here. I believe that what folks are pointing out is that if you run someone's "canned" chip, it's possible you'll see your O2 dropping throughout a run.

On the other hand, if you're fortunate enough to work with a chip maker as Lee did, this condition can be tuned out.

Got it???

 

[Dr. Jeckel]

I was never thinking of it as a chip thing. But if that is the case and everybody running a basic chip has this condition then thats fine. I guess I wasn't reading into his post that way. Thanks for clearing it up for me.

 

[strikeeagle]

Hey Doc,

The chip pulses the injectors. Within reason, the chipmaker can make your O2s look like anything he wants. The rest of the stuff in the fuel system kinda goes along for the ride.

 

[Dr. Jeckel]

Good deal. When I get my new injectors and a chip from turbotweak I'll see what he can do with my setup. I have enough info to make me understand now and not worry that something is wrong. Thanks for all the info for my feable mind.

 

[Ormand]

O2 Sensor effect?

Surprised Bruce hasn't checked in on this. There is a "pressure effect", and maybe a temperature effect too, that causes the stock O2 sensor to deviate from its normal output as exhaust pressure goes up, and maybe temperature, too. That could affect the readings over a 1/4 mile run, even if the A/F stayed constant. I guess that's one of the reasons a lot of tuners use EGT, and pretty much ignore the O2 readings.

 

[Dr. Jeckel]

Here's a stupid question; What does EGT stand for, what exactly does it do, where can I buy one and how hard is it to hook up.
I'd like to get something that is reliable to do tunning by.

 

[Dusty Bradford]

I've spent some time talking with Bob Bailey about this. He spent a lot of time working my chip to get the 02's to stay up with no luck. I have checked my fuel system over and over with a fuel gauge at WOT but they still drop to 720-740 on a 1/4 mile pass. I have a heated 3 wire bosch sensor and have thought of going back to a stock sensor to see if it acts the same way. But Bob's explaination was the extreme heat during a 1/4 pass will drive the reading down lower than what we want but the actual A/F ratio is fine. I plan to take my car to a loaded dyno to see what the real A/F is. Or just buy a WB sensor and install it in the downpipe.