cos3 semi closed loop

[Lextech]

Here is an answer from Ed Wright about fuel trims and W/B readings. "THIS IS FROM ED WRIGHT--I MAKE NO CLAIM TO IT" I'm just passing the info on.

"Don't use a W/B for Non WOT tuning, you're wasting your time. Use fuel trims--Ed Wright"

"If you want to use a W/B for part throttle and idle tuning---Which I don't suggest(you will be very lucky if your fuel trims agree with your wide band) you need to turn off the air/fuel ratio toggling the PCM does most all the time.
To shut that off, set the P.E. minimum temps and RPM to zero, P.E. enable throttle angle to all zeros, and the P.E. vs RPM Air/Fuel multiplier table to all "1"s and the P.E. vs temp table to all zeros. Otherwise your wide band is likely going to be showing you junk numbers, which may or may not be even close to correct. Even then, many of the popular wide bands vary widely.
You would be better off using fuel trims. Wide bands (Accurate ones that is) are only for WOT tuning. If you set the P.E. like I listed you may very well find it is not lean where it now shows it to be lean.


Are you going to leave your vehicle in open loop all the time? If not, as I said before, your wasting your time. The PCM is still going to try to correct it. I'm betting you will eventually find your not lean where you now think you are. Rich will make one "bog down" the same as lean. Bogus lean numbers is what you will see at idle and part throttle, Never Bogus Rich. Less than half the vehicles I have tested over the years will show 14.7-1 air/fuel at idle and part throttle with a wide band. That is unless you set the P.E. parameters as I outlined earlier. That is due to the wide band trying to deal with the rich/lean toggling. See if you have some black on your spark plugs. The PCM won't toggle the fuel rich, lean, rich, lean in P.E. mode. It does that pretty much all the time otherwise. It does that to store oxygen in the cats. Even if you turn C.O.T. protection off, it still does that. If you want your wide band to be correct (assuming it is), put it in full time P.E. mode while you are trying to do your VE tables. When you re finished, and put it back into closed loop, you may very well find (as many others have) that your fuel trims are again whacked. Many guys are trying to tune these like you would a FAST, Bigstuff3, DFI, etc. Those don't toggle the air fuel Rich/Lean like the factory PCM. They aren't as complex as factory computers,and aren't intended for vehicles with cats."

Jeff

[nevinsb]

I don't exactly agree with that. You will see a "bogus rich mixture" if you have a lean misfire condition.

[joecar]

Is Ed saying to enable PE during PT CL and use LTFT's to tune...?

I need a shorter summary of that...

[kostelacd69]

how would i use stft to tune and not the wo2 can a make a map or what sorry im new

[joecar]

Oh... it seems to me that Ed is saying:
- set PE to enable always,
- set PE to stoichiometric,
- now the wideband would show a flat AFR rather than an AFR that cycles tightly around stoichiometry.

The PCM would still be in CL and be in PE at the same time, would that be right...? (interesting)... the PCM would get the AFR from the PE table... and would trim to it but not using the stoichimetry crossings... is this what Ed is saying...?

[joecar]

how would i use stft to tune and not the wo2 can a make a map or what sorry im new

Hi K,

You would disable CL, enable short term triming, map a map of something like 1 + (STFT1 + STFT2) / 400 and apply this to VE or MAF...

but this would only work where the AFR is close to stoichiometry... you can't tune WOT like this since the AFR at WOT is too far from stoichiometry.

[kostelacd69]

right now im tuning wot with my wideband but i havent put my narrow bands in yet so its all been tuned with the wb. i want the stft to work so it has better fuel milage and driveablity. when i put them in i just have to get a map made. can you send me a copy of your map so i can see what you mean thanks

[joecar]

What wideband do you have...?

[kostelacd69]

ive got an intovative the hand held one its what ive been useing for years to tune all my carb stuff. yeah big jump i know

[mr.prick]

Is Ed saying to enable PE during PT CL and use LTFT's to tune...?

[QUOTE=Lextech;97941] "Don't use a W/B for Non WOT tuning, you're wasting your time. Use fuel trims--Ed Wright"
/QUOTE]

It sounds to me that he is saying use LTFTs for non PE
and WBO2 for WOT.
Like this: CLSD tuning with LTFTs
I personally agree with this method, it works for CLSD and CLMAF.
Not only will your LTFTs be inline and
your WOT AFR will be nearly spot on (as long as LTFTs are negative before PE)
but your VE and MAF tables will be smooth if tuning on the street.
You can use the "standard" autoVE process to get your VE table
into the general shape it needs to be with cam and heads/stroker
then use LTFTs and WOT to get it perfect.

Of course filtering is important with this method.
There is no need to use OL all the time,
unless you want to use an emulator to keep fuel perfect.
This is fun and can give you many hours of fun but not
practical for a DD.

My 2¢