Falling O2s

[Dean]

I have a trend of my O2 charts looking like an Olympic Long Jump Ski Ramp. They start way up'n here and drop to way down'n there, very gradual like over a 12 second period. Here's some info from last w/e, with the data provided via Directscan:

Stock 117,000, valve springs & timing set done ~4,000 miles ago. Bolt-ons: PTE52, CAS V2, 50# MSDs, "wired" Walbro 340, T+, 21* Extender (borrowed... have my own coming soon).

All runs with 100 unleaded, base FP @ ~44-45, ~23psi 3rd, ~70-60* ambient temp with relatively low humidity. Converter locked @ ~85 each time. 5 runs, in order:


12.10 @ 113.0, O2s ~.840 to .730, 1.2KR @101mph, T+ WOT fuel set @ 2% lean. Peak INJ PW was 21.58ms / 88.6% @ 106mph

12.16 @ 112.5, O2s ~.870 to .760 , 0.0KR, changed T+ WOT fuel to @ 0% to get rid of KR @ bring up O2s. Peak INJ PW was 22.29ms / 91.0% @ 105mph

12.19 @ 112.4, O2s ~.850 to .730 , 0.0KR, same T+ settings. Peak INJ PW was 20.98ms / 85.7% @ 106mph

12.29 @ 112.2, O2s ~.830 to .720 , 1.4KR @ 95, changed T+ WOT fuel to 2% rich 'cuz O2s were a bit low for my blood on the prior run... it was cooling off. Peak INJ PW was 20.42ms / 85.9% @ 108mph

12.31 @ 112.2, O2s ~.850 to .760 , 0.0KR, changed T+ WOT fuel to 4% to get rid of KR @ bring up O2. Peak INJ PW was 21.93ms / 89.5% @ 105mph

Battery voltage ~13.0 throughout runs.


Questions:

First, if my O2s are showing low 700s, why wouldn't the INJ PW be trying to go higher than it is?

Next, with such a mild setup, WHY would the INJ PW be so high? Could it be insufficient voltage at the pump?? Does someone have some voltage #s for comparison???


I recently went through an ordeal chasing down a problem where I could not reduce my FP to an acceptable level. The problem turned out to be corrosion in the return line where the line is apparently at it's smallest I.D., at the fitting where the line goes from the front of the block into the frame. The line was replaced and all is well. Due to that, I'm suspect of the supply line as well and plan on replacing it too.

 

[Dean2]

Input, anyone??

 

[bruce]

Originally posted by Dean
I have a trend of my O2 charts looking like an Olympic Long Jump Ski Ramp. They start way up'n here and drop to way down'n there, very gradual like over a 12 second period. Here's some info from last w/e, with the data provided via Directscan:


Some sensors do that, that's why it's not a good idea to totally rely on them. If you want to rely on an O2 the get a WB.


Stock 117,000, valve springs & timing set done ~4,000 miles ago. Bolt-ons: PTE52, CAS V2, 50# MSDs, "wired" Walbro 340, T+, 21* Extender (borrowed... have my own coming soon).
All runs with 100 unleaded, base FP @ ~44-45, ~23psi 3rd, ~70-60* ambient temp with relatively low humidity. Converter locked @ ~85 each time. 5 runs, in order:

12.10 @ 113.0, O2s ~.840 to .730, 1.2KR @101mph, T+ WOT fuel set @ 2% lean. Peak INJ PW was 21.58ms / 88.6% @ 106mph

What was the commanded AFR?.

12.16 @ 112.5, O2s ~.870 to .760 , 0.0KR, changed T+ WOT fuel to @ 0% to get rid of KR @ bring up O2s. Peak INJ PW was 22.29ms / 91.0% @ 105mph

Should have retarded the timing a click, if anything, but at 1d your splitting hairs. 6/100 does show a good baseline.

12.19 @ 112.4, O2s ~.850 to .730 , 0.0KR, same T+ settings. Peak INJ PW was 20.98ms / 85.7% @ 106mph

I would have tried a click richer.

12.29 @ 112.2, O2s ~.830 to .720 , 1.4KR @ 95, changed T+ WOT fuel to 2% rich 'cuz O2s were a bit low for my blood on the prior run... it was cooling off. Peak INJ PW was 20.42ms / 85.9% @ 108mph

Cooler air back the timing up.

12.31 @ 112.2, O2s ~.850 to .760 , 0.0KR, changed T+ WOT fuel to 4% to get rid of KR @ bring up O2. Peak INJ PW was 21.93ms / 89.5% @ 105mph

At this stage I would have tried more fuel, less timing, and more boost. All in SMALL Increments.

Battery voltage ~13.0 throughout runs.
Questions:

First, if my O2s are showing low 700s, why wouldn't the INJ PW be trying to go higher than it is?

WOT is Open Loop, you have to make any changes, the ecm is just running on programmed info., there are no feed back corrections.

Next, with such a mild setup, WHY would the INJ PW be so high? Could it be insufficient voltage at the pump?? Does someone have some voltage #s for comparison???

I run a volt blaster and always over 14.
You need to have high PWs so the engine gets enough gas, your at about the limit thou.

Answers hidden in quoted material.

 

[Dean2]

Thanks for your time, Bruce.

Originally posted by bruce
Some sensors do that, that's why it's not a good idea to totally rely on them. If you want to rely on an O2 the get a WB.

Can a WBO2 work with the ECM, influencing the fueling/timing/etc., or would it be a stand-alone reference? I have purchased the components for the DIY-WBO2 offered by diy-efi.org (except the sensor itself), but have not done anything with it yet. I would need in-depth help from my friend Phil H. to do that.

What was the commanded AFR?.

11.6:1.

Should have retarded the timing a click, if anything, but at 1d your splitting hairs. 6/100 does show a good baseline.

Before I had the 50s & TE60, I has 009s & a '49. With those components I ran 26* & 22psi regularly on 100 octane, and weather permitting, 28*. I thought that the 100 octane would be able to handle 21* & ~23psi with the 50s/TE60, and it does, but on the edge.

I strive for 0.0KR, I suppose mostly out of fear due lack of experience. I have read that more KR than what I had can be tollerated without damage, but I choose not to run that risk, even though it may not be the "fast/quick" way to get the job done.

I would have tried a click richer.

If only had I known how much of an effect there would be with ~45 minutes between runs, I would have. The minimum O2s on the prior run looked good, though, so I chose not to change it. With the .730 reading, I was aware enough to bump it another 2% before the next run.

Cooler air back the timing up.

With the INJ PW at 20.98ms / 85.7% on the prior run, I thought the additional 2% fueling would be sufficient without changing the timing. Obviously it didn't, and the INJ PW was only 20.42ms / 85.9%, but that is what I don't understand. Why isn't the INJ PW going higher that this when the O2 feedback is so low???

At this stage I would have tried more fuel, less timing, and more boost. All in SMALL Increments.

That is what i was doing, with only one change at a time so that I would be able to see what the effect was. had i had more runs, i probably would have fiddled with the timing & boost levels.

WOT is Open Loop, you have to make any changes, the ecm is just running on programmed info., there are no feed back corrections.

I am running the Extender chip, closed loop @ WOT... that is why I'm confused.

I run a volt blaster and always over 14.

During regular driving I'm @ ~13.5-14. WOT is the only time it goes to ~13.0. I have heard pros & cons on the volt boosters, with the main con being the fear of running excessive voltage throughout the electrical system. Is this unfounded, in your opinion? If it is not, is there one that can focus additional voltage to the fuel pump only? Are particular boosters/blasters a better design than others?

You need to have high PWs so the engine gets enough gas, your at about the limit thou.

What doesn't make sense, though, is why am I at the limit? At 85% the 50s should be delivering enough fuel for ~500hp, which I am not making. Also, again,why isn't the PW going beyond ~85%??


:-Dean

 

[BEATAV8]

Dean,
My setup is a little bit different than yours, but I have seen the same trends running at the same performance level. I'm running a T+ with 23/21 base chip timing, a TE51, 009's, walbro 340 wired, and all the basic mods, 100 octane sunoco GT all the time, 23 PSI boost.

So far I've found that the WOT MAF settings on the T+ have a big effect on MAF report. The higher settings tend to flatten the O2 curve quite a bit. Right now I'm at 6% rich. At that setting my 009's are seriously overdriven, ~115%-120%, but I'm finally getting enough fuel into the engine in the big end. I'll get some larger injectors soon....

Let me know if you would like to swap some DS files for comparison.

Have a look at the "009's all done 110%" thread for a recent history of my issues/developments.

I plan to install some s10 wheel cylinders and get some new times soon (hopefully 11 sec times!)

 

[Dean]

Originally posted by MJRWOOD
Let me know if you would like to swap some DS files for comparison.

Sure. I'll send some to you now.

Have a look at the "009's all done 110%" thread for a recent history of my issues/developments.

I'm there!


:-Dean

 

[Dean]

Does anyone have an answer, or reasonable explanation, as to why the INJ PW isn't going higher when the O2 feedback is so low???


:-Dean

 

[TurboBob]

where does pulsewidth come from.....

But, here's the deal. All fuel delivered is as a result of the MAF reading.

The ECM takes MAF, divides out RPM so it knows how much air is getting into one cylinder on one cycle. takes this air per cylinder and multiplies it by AF ratio (visible on DS) then converts it to pulsewidth based on injector size. (I left the integrator and BLM out for simplicity)

You are worried about the high O2's early in the run. The fueling is THE SAME early in the run as late in the run if the AF ratio (visible on DS) is the same.

So, why is the O2 higher, because the O2 sensor is cooler. That's it.

We can pull fuel out early in the run (make it leaner) but unless you run a lot of octane you stand a chance of detonation.

Bob

 

[Dean]

Re: where does pulsewidth come from.....

So by fiddling with the MAF WOT switches making the ECM *believe* there is more air, more PW is added.

Presuming what you say about O2 activity is correct, which I don't
doubt as you have considerably more experience and knowledge about this that I do, I would not want to lean it out early as 100 octane unleaded is all I run.

Would a heated O2 give a more accurate representation of what is going on, and would you recommend it? Separately, can a WBO2 work with a T+/Extender setup?


:-Dean

 

[TurboBob]

The WOT switch in the translator (when turned 'up') reports more airflow to the
ECM so the ECM delivers more fuel.

This will probably raise the low gear O2 values as well. But as we have discussed, you aren't
over-rich at the bottom of the track, just the O2 sensor is cooler.

A heated sensor can help this some. Launch technique and brake-torque EGT can help
heat the sensor sooner.

I run a heated sensor, but I cant quantify any gains, My O2's fall thru a run as well.

The final question is what are you trying to accomplish, Attempting to make the
O2 sensor values the same thru the whole run is not practical, nor is a guarantee
of going faster. Most guys tune for O2 readings in third gear.

Hope this helps


Bob

A WB AFR meter is a nice tool, but it won't interface into the Extender.

 

[c&cgn]

Dean, I would sure like to see you using an EGT with your setup. I think it is way more accurate than the OEM O2 sensor and I have found that out on various occasions when trying to correlate the readings between the two.

My car seems to respond really well to EGT's in the 1650* range, and with a frsh O2 that reads around 760-780. When the O2 has had a couple of runs (leaded gas in my case) it shows around 800-820.

Either a WB or an EGT is the way to go. Treating the stock O2 sensor as gospel is dangerous IMO.

 

[c&cgn]

Also, I believe if your T+ is set to rich idle it will throw off the PW reading, and will throw it off even more if you are adding WOT fuel. Mine has read as much as 120% with the 50's and I am pretty sure that I am not out of fuel.

Hopefully Bob will correct me if I'm wrong but that is my understanding that it skews the readings somewhat.

 

[Dean]

Thanks again for the replies.

Originally posted by TurboBob
Attempting to make the O2 sensor values the same thru the whole run is not practical, nor is a guarantee of going faster. Most guys tune for O2 readings in third gear.

How do girls tune?

3rd gear O2s are what I keep an eye on as well, but the readings being so much more higher at the beginning of a run is what got me to wondering if something was wrong. ~.100 seemed quite a difference and I was concerned (hoping??) that I was running so rich that this would be holding me back from an 11. The second concern was why my INJ PW was not increasing since the O2s were low enough to warrant more PW. Now that I have a better understanding of why things happen the way they do, I can devise a plan.

A WB AFR meter is a nice tool, but it won't interface into the Extender.

That's too bad. Can it ever?

Originally posted by c&cgn
Dean, I would sure like to see you using an EGT with your setup...

Either a WB or an EGT is the way to go. Treating the stock O2 sensor as gospel is dangerous IMO.

Looks like I'm heading that way (EGT). I understand there are peak-hold gauges out there, which is probably what I would go for. WB would be nice, and I'll get the DIY one put together, but unless I have a way of recording the data, I'm not sure I would get a whole lot of use out of it without a co-pilot.


:-Dean