Is there any way to run the car in OL just while WOT

[wesam]

Is there any way to run the car in OL just while WOT so the trims will not affect the AFR ?

[ScarabEpic22]

Um, isnt WOT always OL? Yes the PCM/ECM applies LTFTs, but it wont trim based off the O2s.

Look at Swingtan's VVE adjustment tutorial, it outlines what tables need to be adjusted to disabled LTFTs and STFTs.

[wesam]

I know how to disable the trims but i don't want to disable them all the time just at WOT if this possible

[wesam]

Yes the PCM/ECM applies LTFTs, but it wont trim based off the O2s.

.

Will it trim based on averaged LTFTs ?

[turbo]

when you go WOT it will go into OL and if you have LTFT enabled it will add the % of LTFT to the end result. E38 will add and take LTFT from total WOT.

[wesam]

Ok thats what i'm asking about
is there any way to disable LTFTs in E38 just at WOT ?

[turbo]

not sure on that one i always disable LTFTs and leave it disabled, but if you get your VVE or maf spot on LTFTs should be within +or-1% so it wont make bugger all difference at WOT

[wesam]

In FI cars with bigger injectors and aftermarket cams some time the LTFTs will be around -+2% or 3% and that will make a big difference and could risk the car so i want to disable it at WOT

[swingtan]

The E38 WILL NOT go OL at WOT, there is no "semi-OL" like we get in the LS1 COS3/5.

What the E38 will do is go into PE mode, if the correct conditions are met, or it will stay in normal CL mode.

To prove this, look at the OL fueling tables. The settings here are not used any time the engine is in CL or PE mode.

If you are concerned about WOT mixtures, get your fueling correct and run CL STFT only. The E38 will generally correct +/-25% with just STFTs , but you should get them within +/- 5%. If you get the fueling right to start with, LTFT can be safely turned off, but you need to ensure you get the rest right. This includes IAT, charge temp and barometric corrections.

Simon.

[wesam]

How to run CL STFT only?

[ScarabEpic22]

Disable LTFTs is all I believe.

Good to know, I knew it went into PE but I assumed (incorrectly) that it was OL PE.

So once I get the VVE and MAF curve dialed in, LTFTs are essentially not needed for the E38/E67s? If STFTs will trim enough at CL and cruise, then are LTFTs just used by GM to compensate for manufacturing variances between engines?

[swingtan]

Correct, just disable the LTFT's via {B1508}, {B1509} and {B1510}. Leave the rest of the O2 Trim settings as stock and you get STFTs only.

Simon.

[joecar]

( even with the LS1 PCM, WOT is not OL... (positive trims are applied, and OLFA table is not active) )

[turbo]

The E38 WILL NOT go OL at WOT, there is no "semi-OL" like we get in the LS1 COS3/5.

What the E38 will do is go into PE mode, if the correct conditions are met, or it will stay in normal CL mode.

To prove this, look at the OL fueling tables. The settings here are not used any time the engine is in CL or PE mode.

If you are concerned about WOT mixtures, get your fueling correct and run CL STFT only. The E38 will generally correct +/-25% with just STFTs , but you should get them within +/- 5%. If you get the fueling right to start with, LTFT can be safely turned off, but you need to ensure you get the rest right. This includes IAT, charge temp and barometric corrections.

Simon.

i better fix what i wrote that it adds LTFT to the PE.
Simon how do you mean is never goes into OL ? you have me thinking now bugger it

[wesam]

( even with the LS1 PCM, WOT is not OL... (positive trims are applied, and OLFA table is not active) )
Do you mean just the positive trim that will added ?
so no negative trims will be subtracted ?

[turbo]

apparenty E38 will subtract it if the LTFT is -

[wesam]

apparenty E38 will subtract it if the LTFT is -
What about LS1 ?

[turbo]

as far as i know LS1A controller will only add+

[swingtan]

Simon how do you mean is never goes into OL ? you have me thinking now bugger it

I mean, it never goes in to OL mode. There are three basic fueling modes...


Open Loop: as expected, no fuel trim correction is used. Fueling is controlled solely by the VVE / MAF and injector flow data. Commanded fuel ratios are set with the tables under the "<Engine Operation> - <Fuel> - <Open Loop" section, which derive an AFR from the base stoichiometric setting in {B3671}.
Closed Loop: Again, as expected, fueling is controlled by the closed loop trims, as they take input from the NB O2 sensors. Fueling is initially set via the VVE / MAF and the ECM will cycle the mixtures through rich and lean conditions to average a correct stoichiometric level ( as measured by the NB O2 ). Commanded fuel ratio is set via {B3671} "<Engine Operation> - <Fuel> - <General> - <Stoichiometric AFR>"
Power Enrichment: When the conditions are set for PE mode, the ECM enters PE mode to provide additional fuel when under load. It is not OL mode and is not CL mode, it is PE mode. Again fueling is controlled via the VVE / MAF, but also may have LTFT data applied if it's set that way. The commanded fuel is set via {B3618}, <Engine Operation> - <Fuel> - <Power Enrichment> - <P.E. Mode Commanded Fuel>". It does not use the OL fueling tables at all, it actually uses a {B3618} to modify the Stoichiometric value set in {B3671}. So this indicates that PE mode is actually a modified CL mode.


As for using both +ve and -ve LTFT's in PE mode, I can't remember now. It's been a number of years since I ran LTFTs in my car and at the moment I'm running full OL-MAF while running E85. I do however still run PE mode, so that further indicates that PE mode is a completely separate fueling mode from both OL and CL.

Simon.

[joecar]

Do you mean just the positive trim that will added ?
so no negative trims will be subtracted ?


What about LS1 ?Correct, LS1 applies only positive trims in PE mode, rounds negative trims up to zero.

[joecar]

For LS1:

By setting the OLFA and PE with different curves that cross each other at a single "point", we have done experiments that show this:
- from CL, going WOT enables PE but not OL (the PCM has a CL-PE mode where it is applying the last remembered trim);
- from OL, going WOT enables PE in OL (the PCM has PE and OL both active, it uses the richer of the two tables at each operating point).

More info, see post #4 here: Summary-Notes (http://forum.efilive.com/showthread.php?14188-Summary-Notes)


LS1: in PE applies only positive trims
E38: in PE seems to apply negative trims also.


Also note that in PE mode the trim is applied, but the trim itself is not updated (with NBO2's).

[wesam]

So the average trims will be applied in E38 at WOT ?

[joecar]

So the average trims will be applied in E38 at WOT ?No, that's not what swingtan said.



...
the ECM will cycle the mixtures through rich and lean conditions to average a correct stoichiometric level ( as measured by the NB O2 ).
...

i.e. the ECM manipulates the trim to find an average stoichhiometric AFR.

[wesam]

Ok i will give you a scenario a bolts on E38 with stock injectors and MAF
car running CLMAF
LTFT reading -5 @ cruising
MAF corrected just @ WOT to be the same as commanded AFR of 12.7
if the LTFT changed for any reason in the future will the WOT AFR changed or it will still the same because the MAF corrected while tuning ?

[swingtan]

It depends on what the LTFT's were reading during WOT. If you're dialing in the MAF, I'd just disable LTFT learning and clear the learnt data. Then run CLMAF, with only the STFT's.

Simon.

[wesam]

It depends on what the LTFT's were reading during WOT. If you're dialing in the MAF, I'd just disable LTFT learning and clear the learnt data. Then run CLMAF, with only the STFT's.

Simon.
So you recommend to disable LTFTs all the time and running CLMAF with just the corrections applied with STFTs all the time ?
If i doing that in some cars i need to correct the MAF because the AFR will be away from the commanded and this will take some time
isn't there any way to just keep LTFTs off while WOT ?

[swingtan]

Basically, no. What you can do is enable / disable the LTFT learning, not the LTFT application. So you need to disable the LTFT's from learning any correction data. To be honest, the art of tuning is all about correcting the engine fueling first, then correcting the spark advance. In my opinion, you should be correcting the fueling in all vehicles that you are "enhancing" the standard tune in. Thinking that the STFT's and LTFT's are going to pick up the slack is not the way I'd go.

The only advice I can give you in youre situation is to log the LTFT's during PE mode and see what value they are using for correcting the fueling. If it's negative, then the fueling will get richer if the trims change and go positive.

Simon.

[wesam]

what if LTFTs in cruiseing and WOT are the same ? both -5 ?

[joecar]

Ok i will give you a scenario a bolts on E38 with stock injectors and MAF
car running CLMAF
LTFT reading -5 @ cruising
MAF corrected just @ WOT to be the same as commanded AFR of 12.7
if the LTFT changed for any reason in the future will the WOT AFR changed or it will still the same because the MAF corrected while tuning ?If the LTFT changes then this would mean that the ECM has detected a change in conditions and would apply the LTFT to WOT in an attempt to keep the actual WOT AFR the same.