O2's dropping at wot...2nd new denso sensor

[Dr. Jeckel]

Well I got a desno O2 sensor about 2 weeks ago and the cc's we're super slow and the O2 readings would drop at WOT so I finally decided to get it warrantied and they sent me a new one and now the cc's seem to be doing ok but the same thing at wot.....860 to 850 to 830....all the way down to 770 before i get out of it. It is slow and I was told that this is a sign of a bad O2 but what is the chance of getting two bad ones especially since I seem to be the only one who has gotten a bad one.

Is there anything else that could cause the O2's to drop.

The only reading that is a little out of the ordinary is the BL reading is about 124 at idle in park but it goes to 128 at WOT and stays.
I don't remeber my stock O2 sensor giving these readings but that was before I added the chip and LS1 maf and translator.
AF readings are good and everything else seems to be ok.
I get 2-3 degrees of KR after I floor it because the boost spikes to about 17psi then goes right down to 15psi and after about 2-3 frames the KR disappears.
All WOT runs were done in 3rd gear.
I am running 44psi line off on fuel pressure.

Need some help on this one...what are possibilities?
Thanks, James

 

[Royal-T-Ltd]

Is there anything that could cause the 02's to drop?

YES...BOOST! It is normal for your O2's to drop at WOT as long as there is NO KR - you will be fine. Most people shoot for 760-780 range. And about your BLM's at idle being 124 - most people would kill for that too. Most chips incorporate a BLM lock at WOT to 128 which is where you wana be throughout the power band that is right on for A/F ratio. YOU ARE FINE.
ps How much boost are you running?

 

[Sleeper-6]

Now you say 760-780. When should I be seeing those numbers? the whole pass, or the end of the quarter mile?

 

[Royal-T-Ltd]

3rd gear - end of pass- some people like to stay on the richer side maybe closer to the 780-790 range but as long as there is NO KR - the leaner the meaner - You MUST watch your scan tools though!

 

[Dr. Jeckel]

I was always told that the O2's are supposed to stay solid at WOT. I read countless threads where this was stated.
Your O2 reading should have a direct conection to the fuel you are putting in, so if they are dropping then that means not enough fuel is being added....isn't that correct?
If you are only supposed to shoot for 780 at the end of the pass then I guess I have to wait for a track to open up.

 

[Royal-T-Ltd]

Yes in a "perfect" world our cars would have the perfect, linear - stoichiometric - A/F ratio ALL the time in ALL gears, but in real world driving. Chip programming, fuel pressure, tuning, weather conditions ALL effect A/F ratio. Usually cars will be rich [read-higher mV O2s on the lower end] and as boost develops and you reach higher gear the mV from theO2 sensor will go down. As long as it settles at a safe range on the top end and there is NO KR you will be fine. To Answer your question "YES!" wait til the track opens and see -or- find a long straightaway (hopefully with NO law enforcement officers) and bury the hammer. JUST MAKE SURE TO WATCH SCAN DEVICES! HTH

 

[Dr. Jeckel]

As long as it settles at a safe range on the top end and there is NO KR you will be fine.

I might have misunderstood the statement, but the point is that mine doesn't settle. I get to about 65mph in thrird gear and hammer it and the mv readings go from 853 down slowly to 770 and never stop....when I had my stock O2 sensor the readings went to 820 and stayed rock steady during a 3rd gear punch at 65mph.
I'm not talking about doing a WOT run starting from a dead stop. I realize that A/F ratios would change there.

 

[Royal-T-Ltd]

What do you mean "Never stops" how far have they gone down BEFORE you let off AND was there any KR? Do you have an EGT gauge?

 

[Dr. Jeckel]

Once it gets to about 770 I get out of it. I have no idea how fast i am going , but I am still in third(rpm gauge is reading in the red on stock gauge). there is no knock and I am using the SM2 for knock reading...no egt gauge. But it does even come close to settling...it drops from an intial 850(or so) when I hit it by 10-13mv's per frame on the Scanmaster.

 

[Royal-T-Ltd]

I didnt see or missed it but do you have a F/P gauge? that you can monitor while mashing the gas. If you do - is it corresponding with your boost? Still if your not Knocking.... put your delco O2 sensor in and see what its reading. You are obviously not running race gas so the stock one should be fine anyway.

 

[Dr. Jeckel]

I do have a rail mount FP gauge. I think I will try the ac O2 again and see what happens. I wanted to get the denso so when I put alky on it, i'll be ready.
Has anyone else had these kinda problems?

 

[Royal-T-Ltd]

Try to run a s/s braided hose to your windshield so you can verify your F/P. and there is no problem with running alky and a delco O2 sensor [i do]. People are using Denso's b/c they tolerate leaded race gas.