can I VE tune like this??

[maudyZ28]

How would this work (dont have a wideband currently but will have to get one)

Dissable the MAF
Run off the VE table but increased 10% everywhere (called CLSD right??) -- (use LTFT to get BEN or WB later)
Correct VE table and check (drive but not entering PE mode, where is safe not to ask for PE enrichment, its hard to hit high rpm cells with high MAP without going into it)
How can you adjust timming here??

After VE set:
Set PE to 12-13 ish (after I test the best fastest burn point where i start to get knock on stock timming table - discussed in other post)
Set timing so there is no knock with a PE AFR range between 12-13

Do i really need a good VE to sort out PE mode, doesn't the MAF become exclusively used above 4000 rpm thus NOT using PE at all?

[swingtan]

1. Using any trims will allow you to adjust the VE table BUT only in cells where the engine is running in closed loop.
2. PE mode is basically Open Loop, so there will be no trim data for these cells. ( LTFT's are active but the amount is worked out from the CL fueling )
3. Yes, you really need a good VE to get PE fueling correct, because you have disabled the MAF in an earlier step. Even if you re-enable the MAF, you still should check that the MAF is reading correctly in all zones. So the idea would be to perform a full VE adjustment and then do the same thing for the MAF.
4. Before any spark optimisation is performed, fueling needs to be correct.

Basically, you need a wideband O2 to do the job right. If you really want to start tuning now, then do the right thing and log lots of data before altering anything. Use the time until you get a WB to learn how to log the data you need and learn how to interperate the data logged.

Simon.

[maudyZ28]

ok, so if PE is enabled by throttle % in gear then that is OPEN loop too, such that there are no STFT or LTFT actually acting upon the fuel mix

I understand how the trims are wrong too, i did a log following calc_VE which I understand how it works but wondered why in PE the calculated VE decreased, clearly as you say because it was thinking it was stoich fueling so said there was too much fuel as it was in PE commanding more. So I can only do PE 'properly' if I have a WB

Also, if I run MAF only enable at 400 rpm or less, then correct this based upon BEN from LTFT not in PE mode, assuming the O2 switch points are set up for stoich fueling then i can 'trust' the corrected MAF signal and then have to trust that it is commanding 14.63 in CL MAF and so when it goes to PE using MAF it will be asking for PE enrichment value, set between 12-13

In short, if MAF is true (based on LTFT) I can do PE by asking for an enrichment, seeing and see how the car runs

Finally, i know the 99-00 LS1 timing is really aggressive, if the VE and MAF are calibrated (thus assume fueling is correct), and I were to get knock at part throttle would you point to running too much timing.

How much would you trust the narrowbands and MAF calibration??? I dont want to run the car lean and detonate it

[swingtan]

That's not quite what I said......
It doesn't matter how PE is enabled, any time you are in PE mode, the O2 sensor feed back is not used. remember that the narrow band O2's can only switch between a rich and lean condition at a lambda of "1" ( for ULP that's 14.63:1 AFR ). Any time the AFR goes rich or lean, the O2 sensor simply peaks out it's signal. So the narrow band O2 cannot give any accurate AFR indications while in PE mode ( unless you command 14.63:1 and even then it won't be particularly accurate.)

The thing is though, that while the PCM is learning trims while in CL mode, these trims ( LTFT ) are still applied during OL fueling. So if your VE table ( and MAF ) happens to be on average lean, the LTFT's learnt in CL also help to richen up the fueling while in OL mode, which includes PE. Given that the VE table acts as a "sanity check" when using a MAF, correcting it in the CL cells will possibly influence the LTFT's, bringing them back closer to "0". If you are running with no MAF, this could result in an overly rich or lean mixture when PE mode is enabled.

When running MAF only, you still need to adjust the MAF calibration to ensure that the MAF frequency signal is correctly interpreted for the amount of air entering the engine. Remember that the MAF signal will change with engine load and that the same OL / CL conditions still apply. So yes, you can use LTFT's and STFT's to correct the MAF calibration while you are running in CL, but this will also impact your PE fueling as the LTFT's are reduced back toward "0". You still can't get any accurate data for OL mode at all, so you are still stuck when trying to do any corrections for the MAF calibration in OL mode. the MAF being "true" at the bottom of it's scale does not mean it is "true" at the top of the scale.

As for trusting the NB's and the MAF? I trust the NB's in CL mode only and basically ignore the actual reading in OL mode. The MAF I trust, but only because I've spent a great deal of time calibrating it. If you don't want to run the car lean and risk damaging it, then don't make changes until you have the WB. Then you will know what mixtures you are getting rather than just guessing.

Simon.

[maudyZ28]

thanks Simon,

I didn't realize the LTFT were still applied in PE mode.

In the idea situation then I would disable LTFT and use a WB to get fueling right, exclusively from the MAF or VE via autoVE or auto MAF. Once I know these are correct and the commanded fuel is the actual, this would apply to the full table as the BEN uses the ratio between commanded and actual regardless or running in PE mode or not

Do many people re-enable LTFT after this as these go back to correcting via the narrow bands?, I assume if both the MAF and VE are the same then you wouldn't need to or if you do the trims are ~0 anyway.

I have noticed when looking at different stock tunes, the corvette C5, Z06 and camaro, that the corvette Z06 has a flat O2 switch point for all CL modes, but the C5 and camaro vary from like 235 mv at CL mode 8 and go upto 465 mv at CL mode 60 and then up and down etc etc? With a WB to I want to set all these to the same such that the LTFT BEN matches the WB BEN?? Or are the stock O2 points set up correctly?

Also can I put a WB in just before My X-pipe?? or would you put it more in the collectors of the header. I have a separate bung for it

[joecar]

In PE/WOT mode, positive LTFT's are applied, negative LTFT's are not.

Place the wb as close to the engine as you can to reduce any time delay effect (exhaust gas travels at some finite velocity, time=distance/speed).

Some of us just run OLSD all the time, while others get better results by going to CLSD or CLMAF... you have to try and see.