rel3rd

iTrader: (42)

So, both of you just used your widebands to dial in all fueling?

Sorry I had to talk about "foreign" cars here, lol. But they are what had that maf only question sticking in the back of my head for about 3 years now. What sucks is that when I originally tuned my truck, I spent roughly 5 hours "street tuning" it...4 hours of that were logging and dialing in the VE table, and just an hour or less of MAF tuning. Re-tuning both tables after my header swap went much quicker, but I'd much rather get it dialed in faster right from the get-go if it's providing good results.

KLUG'S SS

iTrader: (6)

You should just be dialing in your maf and or ve tables in open loop with a wideband regardless. You NEED the wideband hooked up anyways for WOT tuning so why not just do it all in open loop.

Tuning with fuel trims is ok but the narrowband sensors have a "deadband" error of about 3% and they don't switch until they are actually past the target.

Tune everything in open loop with the wideband and then when you go back to closed loop if you wish then your fuel trims should settle within 0%-4% if evrything was done right. Dont pull your hair out trying to get them to 0% because it wont happen as they can vary by a couple percent day to day.

And yes their is nothing wrong with leaving LTFTs disabled and just going off STFTs. I know ALOT of good tuners that do it this way.

rel3rd

iTrader: (42)

Main concern was whether or not to re-enable LTFT's when running MAF only.

So far, the consensus is to leave them off, which I did, so I'm going to run it this way for the time being and see if I come across any reason to change it back.

KLUG, I thought I read that you run maf only as well? Do you see any reason not to?

BlackGMC

iTrader: (31)

From my understanding running a MAF only tune will tend to have problems with the throttle transitions, like lean/rich tip-in (transient Fuel Tuning comes into play here as well), etc... I have read/told that the VE table becomes important when the throttle changes are too quick for the MAF to pick up so it reverts back to the VE table....

Atomic

iTrader: (42)

You cant disable the VE table and there is really no point even if you could if you still have a MAF. The VE table gets referenced between high transitions, like flooring it from an idle where the throttle body is opened but the airflow hasnt increased much yet. As long as the VE is somewhat close you will be fine.

I disabled LTFT for everyday use. My short terms are dialed in pretty close so the long terms dont serve any purpose.

rel3rd

iTrader: (42)

I have read/heard that too, but can't understand why I am NOT having any problems whatsoever. Truck is much more responsive at any cruise rpm, or from idle/dead stop. Just verified again with a quick drive to the store and back. The truck has never ran so well, or felt this strong running all around. FWIW, my VE is tuned well within the + or - 5% threshold, even though it shouldn't be used in my present tune anyway.

From what everything/everyone says, below 4000 rpm, these vehicles use "hybrid", or blended, calculations from both the VE and MAF. Above 4000 rpm only the MAF table is referenced

If that is correct, than this setting:

Engine > Airflow > Dynamic Airflow > High RPM Disable > 0 rpm
(which is changed from stock setting of 4000 rpm)

Eliminates the PCM referencing the VE table unless the MAF meter actually fails? If it doesn't, then how would it even be possible to tune a MAF table that is also being influenced by the VE table's calculations?

Atomic

iTrader: (42)

From my understanding the primary source of airflow data is the MAF in all cases. I believe the blended use you are reffering to is what the High RPM disable setting does. Below that setting it uses a blended calculation and above that it uses just the MAF. The MAF doesnt work well at low engine rpm because it needs relatively stable airflow to get good readings, and flow at low speeds is rather unsteady hence the need for the VE table.

I believe its 4000rpm cutoff because unless you are running very low throttle above 4000 you are going to have high-speed laminar airflow across the sensor which is the ideal situation. Low-throttle and high rpm dont usually go together unless you are doing something weird.

BlackGMC

iTrader: (31)

Lets look at this from a Airmass Calculation standpoint...

Here is the definition according to EFI Live....
I believe that is pretty self explanatory... If running VE and MAF, the PCM updates a correction factor, but according to the definition, it does not use it during steady state crusing, however the correct factor appears to added to the Airmass Calculation when rapid throttle transitions occur...

Now, if your running a MAF only or VE only tune, this correction factor (Whatever the hell it is) is not applied to the AirMass calculation...

So IMO this is what you get...

VE only (Speed Density), the cylinder Airmass is calculated by this equation g/cyl = VE*MAP/charge temperature which would only update if the Charge Temperature (IAT and ECT changes), so this is a calculated result

MAF Only (Direct Aiflow), measures airflow directly and converts it into g/cyl, so this is a direct result, which under steady state airflow it is accurate, under large throttle transitions it becomes inaccurate, which can be seen by any log....

So that brings us to a Hybrid, VE + MAF, meaning it blends actual and calculated, when needed...


Just my opinion, probably not worth .02, but hopefully it makes sense...