devilfish

I read TRAXION topic about "non pe tuning" 1 year ago and applyed that to my car. But conisder this "news" about the difference between a WB readings and the stock NB and closed loop BLMs, can I still apply that?

Or can some explain to me how you now tune idle and "crusing" ( non PE ) modes when a WB says one thing and the NB and BLMS another?
Is the only way to tune non PE to lock the ecm in open loop?

Lets say I got BLM at 128 in closed loop at 2300 rpm @ 52 kpa, or what ever. BUT my WB reads im lean?

All this new info really driving me nutz, after 2 years following this forum I thought I started to understand this. And now this.......

conv90

I'm in your same boat...
The difference is that I'm STARTING tuning VE tables.
...And now i'm not sure if what I learned in 6 months of "learning mode" in this form is still true..
I was starting to change VE tables for non PE tuning (idle and cruising) but now I stopped myself..
With the closed loop/BLM method I have to decrease all VE values, and with these "news" on lean WB readings vs. NB readings (even on cruising not only at Idle...) I'm a bit afraid.
I like to see that there is more than one approch to tune an engine...what i'm afraid about is that these two differents methods goes to opposite directions.
BLM NB closed loop way.
If I have a 110 BLM at 2500rpm at 50 MAP I have to dercrease tha value of 70 to about 64.
open loop WB way
WB shows 16:1 AFR
if my target is 14,7:1 AFR I have to increase the value of 70 to about 76.
64 is far differnt from 76!
I have to stay with the stock 70 value and put in the trash the chip burner, the ALDL cable, the laptop, and the fun I was thinking to have tuning this engine?
I seen in this forum people going "religiously" to put BLM's in 128 range in closed loop.. and now ?
-Beppe-

contactpatch

For cruising, I would be tempted to trust the NB, cuz
thats its only job.
.
Would there be any chance of operator error with the
WB, such as air leak or smog pump on?

Ronny

iTrader: (1)

this is a good topic. my wb02 has been in box for 6 months and finally going on thursday-friday this week. as was explained to me the NB 02 cycles the A/F ratio over(rich/lean) 14.7 for cat/conv reasons and emishions. in cruise i guess i would have expected the WB to show 14.7. i believe the senors(WB/NB) are exactly the same distance from my exhaust ports which is after my header collector in pipe. i believe that is further from "stock" location was. i further believe my GM 02 is reasonably accurrate in cycling around the "stoich". now the fact they are further downstream probably will have an effect on the NB02 function. what effect is i dont know. my deacceleration enleanment is functioning. what does that have to do with leaner than expected wb readings?. something i presume. i do have a baseline with "narrowband" on dyno verified by dyno WB. i believe it was near 14.7/1. and a baseline with PE WOT on dyno. 12.0/1 showed. i guess i will run CL and only use the WB for AE tuning and PE. i willlook at the "cruise" A/F and if alarmed will consult the xperts(YKWYA).... anyone care to expand this topic??

devilfish

I started this topic, cause this "news" about WB readings vs NB and BLMs made me loose almost all hope of EVER understand to tune the ( in my case 730 ecm ) GM efi systems.
You heard it all over , "give the engine what it whants". Face it , you cant, at least if you would like to use the GM efi the way GM intend to use it.
For my case, I drive a 1991 6psd corvette, I done head/cam/intake/exhaust/ fordge rotating assembly.
I drive this car 3-4 days a week. I use a cat.
I "must" tune non PE crusing at a 14.7:1 A/F or close, to keep the cat happy.
I used the NB to tune the BLMS close to 128 cause I thought that would keep the cat happy, as it should be a commanded A/F of 14.7:1 or close. Now with a WB connected I can se clearly that becuase of my mods the "code" inte ecm to keep the car close to 14.7:1 using closed loop no longer work as did when my car whas stock, ( well atleast i THINK it worked when my car whas stock, dident have a WB back then ). I also verifyed this when I look at pugs etc.
In open loop my car runs soooo much better. BUT I cant really use open loop cause I use a cat. Sure I could tune non pe using the WB and "force" the ecm to stay in open loop all the time. But I dont know if thats a good solution? I like closed loop, feels "safe" to know the the ecm try to keep the cat happy under diffrent conditions.
The only "solution" for me is to change the commanded A/F in the chip, to something else that match 14.7:1 on the WB.

Perhaps I just worry to much. Just let the blm be at 128 even though that the car ( in my case ) is running super lean?? But I really dont like that ide either.
Or perhaps Im just to stupid to ever learn this.
In that case, sorry for takeing your time..

regards