MAF Calibration (No Spreadsheets!)

[SSpdDmon]

Bruce
Have you seen this across the board or down low where the VE and MAF are "blended"?

I'm pretty sure I noticed this at WOT too. It's been a while since I've played around with this, but I'm pretty sure that's the way I remember it. The funny thing is, applying the full correction down low where the VE is referenced actually over corrected the MAF.

[Bruce Melton]

Yes, on over correcting the MAF. I sent two hours udating AutoVE then immediately made MAF runs and applied to stock MAF table. The result after plugging this all into a fully MAF/CL enabled tune was AFRs generally above 15 to 16 except in VE where they were 12.5 to 13.4.
I see the problem as adding MAF air where it is not needed. We tune for no MAF then add table for MAF to fill in where no gap exsists.

How wrong would it be to AutoVE with stock MAF table enabled?
Would the resulting VE MAP be adjusting VE (+ MAF) = final AFR? If so, that sounds like a winner for those of us who are MAF challenged.

[Tydriver]

Dhayang !! Thats good stuff.. I need to try it out..

Hey, Chad, you ever get a chance to look at that TUNE I sent ya ?

[SSpdDmon]

Bruce - You can't AutoVE with the MAF enabled. That's the inherent problem. You kill the MAF to get an accurate VE...then re-enable the MAF and get an accurate MAF with the assumption the VE is still good. I guess you could kill the VE with B0120 set to a number below idle while tuning the MAF. But, it might not be accurate enough at low airflow scenarios. I plan on experimenting with this at some point (if I ever get my car on the road again).

[Bruce Melton]

It seems as though (in theory) that once a good VE is AutoVEd that the VE table should be reduced by some percentage to allow more room for a more normal amount of correcting MAF air. The MAF is a major player in the factory tune's ability to lock in all-weather AFRs. Seems we are limiting it's positive influence.

Solving backwards from desired AFR is the purpose of AutoVE but we are forced, it seems, to leave out the big equalizer.

Ok, I am done.

[SSpdDmon]

It seems as though (in theory) that once a good VE is AutoVEd that the VE table should be reduced by some percentage to allow more room for a more normal amount of correcting MAF air. The MAF is a major player in the factory tune's ability to lock in all-weather AFRs. Seems we are limiting it's positive influence.

Solving backwards from desired AFR is the purpose of AutoVE but we are forced, it seems, to leave out the big equalizer.

Ok, I am done.

My understanding is, airflow is airflow. The PCM will calculate fuel based on what we tell it. Kill the MAF so only one variable is in the game (VE). Once VE is dialed in, it's no longer a variable assuming it's dialed in correctly. Then, the only variable left should be the MAF once re-enabled. Tune the MAF and it should be able to compensate appropriately just like it did from the factory. Reducing the tuned VE table will most likely lead to lean transient fueling according to what I've read on the boards. So if anything, I'd think you'd want it increased slightly.

Then again, I talk to other tuners (who seem to know some of the engineers here at GM Warren Tech Center) who say you should have the MAF flowed for your setup and leave it. Then, adjust the injectors for appropriate fueling. That trends back to the older way of doing things. But, they seem to be making all of the power. The last car he just tuned was a Mustang with a twin-turbo kit and upgraded fuel system. The damn thing made good power and 25mpg on the 1000+ mile trip home. So, I don't know which way to tune anymore... I kind of like the idea of getting the AFR dialed in for the most part in less than 4 hours instead of 4 weeks. However, it does seem frowned upon with a lot of the do-it-yourself tuners.

[Bruce Melton]

IMHO the results achived by AutoVE are the foundation for a lifetime tuning hobby. The results can be great but reqiure "tune of the day" (TOTD) for optimum drivability and peak power.

I have done it both this ways and "old school" and with diddled IFRs, was much more repeatable but the transitions were poorer than a fresh AutoVE. It also did suck up Injector capacity, but then again I am fighting loafing low end 42s now.

What VE table does one start with for a home brew 402 for instance?
For a lighter head and cam car that is not an issue but when you do bigger or more radical motors it is murky to me.

In the end a pretty PE enhanced, WOT AFR wins races and makes dyno queens?
How to get out the the TOTD hobby?


Did I say I was done last time?

[1998ws6]

The OEM aproach of having the intake track flowed as an assembly and using that MAF calibration is probably correct, but how many people have a flow lab where they can have this kind of work done?

For tuning that mustang, depending on what kind of tuning software was being used, they were probably provided with correct injector flow data from the company that provides the tuning software, so that would be the value that I would take more faith in, and adjust the maf.

At the end of the day, you need to ask yourself, what factor do I have the least confidence in being correct. On a stock LSx car, I would say the injector flow data is correct, as it came from a flow lab as well.

Just my 0.02

Ryan

[98SS2836]

Does anyone have this map it seems the attachments are too old to down load.

[SSpdDmon]

You can make it fairly easily. Open the scanner and the tuner. Create a new map in the scanner. In the tuner, right click in the upper left grey cell (so the entire MAF table turns blue and a menu pops up) and select "Copy with labels..." In the scanner, select MAF Hz for the rows and click on the Paste Labels button. For the column, select RPM, set the number of columns to 1, and then type ",8000" for the labels (yes - type the comma too). The data values you want to use depends on how you're tuning - BEN for your WBO2 if you're using one or LTFT/STFT's if you're using the stock NBO2's (not recommended for anything other than normal, closed-loop operation). Simple enough...