Extender - REALLY closed loop?

[Dean]

This sounds like a stupid Q, but since I can't get the info I was looking for on another thread, I'll ask...

When the Extender chip is in closed loop, is it REALLY closed loop, in that O2 information is still being referenced in the fueling calc's @ WOT?

I'm trying to find the reason as to why my O2s drop ~.100 from start of run, and why my O2s are going so low at the end of a run (like in the 720-730 range), and there is still some INJ PW to be used? Typically there is ~2+ms to go 'till I get to 100% DC.

Example: 3rd (locked), 111 mph, 5200 rpm, 19.93 INJ PW, 86.4% INJ DC, .733 O2s.

I have many exapmles like this, not a once off.

 

[Steve Y]

Sometimes you can have a fuel curve that gets richer toward the end of the quarter and the 02's will drop because the egt is climbing.

The 1 wire 02 reading is relative to egt.

The car will not learn at wot but typically goes by what it learned in the last cell.

I suspect Bob may lock that cell at 128 at wot.

Hope this helps.

Steve

 

[ijames]

First off, when TurboLink or DirectScan say "closed loop", they are reporting the state of a flag in the ecm. That flag does not mean that the ecm is running in closed loop, it means that based on coolant temp, O2 activity, and engine run time it is okay to go into closed loop mode if other parameters don't prevent it (such as ae, pe, deco, dfco). Second, no chip I'm aware of looks at the O2 sensor voltage when in PE mode. The basic fueling equation is:

inj pw = maf * blm * int * desired far * (1/rpm) * (battery voltage and cold start trims)

In PE mode the int is set to 128 and the pe-rpm and pe-tps trims are also multiplied in. PE-rpm is a table of fuel vs rpm, and the values in that table will determine if the engine gets leaner, richer, or stays the same as the rpms climb through 3rd gear so even if the maf isn't pegged so the ecm can measure the airflow and even if the inj duty cycle isn't 100% so more fuel is available if that table doesn't say to add it, it won't. The blm is often locked to some value so changes in fuel pressure are reflected in the wot fueling so you can tune, but that won't change the shape of the O2 volts vs rpm.

 

[bruce]

Originally posted by Dean
This sounds like a stupid Q, but since I can't get the info I was looking for on another thread, I'll ask...

When the Extender chip is in closed loop, is it REALLY closed loop, in that O2 information is still being referenced in the fueling calc's @ WOT?

I'm trying to find the reason as to why my O2s drop ~.100 from start of run, and why my O2s are going so low at the end of a run (like in the 720-730 range), and there is still some INJ PW to be used? Typically there is ~2+ms to go 'till I get to 100% DC.

Example: 3rd (locked), 111 mph, 5200 rpm, 19.93 INJ PW, 86.4% INJ DC, .733 O2s.

I have many exapmles like this, not a once off.

The O2 has no direct bearing on WOT fueling.
If your running a Boasch ensor that well can be it.
EGT, and EBP can effect the NB O2 sensors.

Try going up in fuel pressure. 86% is about it unless you subscribe to the static society.

 

[Dean]

Originally posted by Steve Y
...

Thanks for your input, Steve.

You may very well be correct. I do not have an EGT gauge, though, so I'm in the dark there. It has been recommended several times by several people to get one, but my car is very stock looking and I want to keep it that way. besides, sometimes I don't even look at the boost gauge in the heat of the run, so looking at another gauge is highly unlikely. Perhaps I could hook one up and keep it under the hood, and then pull it out when I'm at the track...maybe a magnetic base kinda thing.

You mention that the 1 wire 02 reading is relative to egt reading. How so? Is there a chart that could "ball park" it? You also mentioned that you suspect the last cell is locked at 128 @ WOT... upon re-reviewing my DS files, I see that this is correct, and I hadn't noticed. Cell 15 in the table doesnt change, but the BLM readout above does as soon as PE is applied. Thanks for making me realize that.

Originally posted by ijames
...

Carl, that is exactly what I'm trying to confirm. Is it really, truly, completely closed loop, or is it sorta (due to mitigating parameters), but the flag remains.

BTW, I tried running the fueling equation you have listed, but got stuck on the last item... don't know what the cold start trims are.

Originally posted by bruce
...

Bruce, thank you again for your input as well. I am running a stock AC Delco 1 wire sensor. And no I don't want to run static or jack up my FP (currently set @ ~44), putting additional strain o the pump. It doesn't seem like an appropriate thing to do. I just wanted to figure out why my car is doing what it does.



:-Dean

 

[Steve Y]

Dean,

The hotter the 02, the leaner it reads for whatever reason.

A Buick engineer put it to me this way once.......you could be running 11/1 with an 805 02 reading at 1100 egt and 12/1 with a 800 02 reading with a 1300 egt.

I am sure he was pulling numbers out of a hat at the time, but put it to me this way so I would understand.

That is why when you see the 02 drop at the end of the 1/4 it does not actually mean the fuel is getting leaner........

Steve

 

[ijames]

Originally posted by Dean

Carl, that is exactly what I'm trying to confirm. Is it really, truly, completely closed loop, or is it sorta (due to mitigating parameters), but the flag remains.

BTW, I tried running the fueling equation you have listed, but got stuck on the last item... don't know what the cold start trims are.


:-Dean

You asked about WOT. At WOT you are in PE, and therefore not closed loop. The flag remains set to "closed loop" because all the other tests pass so if you weren't in PE you would be running closed loop. The way to tell if the ecm is actually operating open loop or closed loop is to look at the INT. If it is fixed at 128 the ecm is running open loop. If it is bouncing up and down then the ecm is in closed loop and using the INT to toggle the O2 sensor rich and lean.

 

[Dean]

Thanks again, folks.

:-Dean