desTRUCKtive

Mods: 6.0 with a TR224.

I have been tuning my truck on SD, and I have gotten all of my LT down to zero. I tuned the entire table in this mode. I now want to calibrate my MAF. Well I did some logging and recorded my MAF hz and Dynamic Cylinder Air in lb/min. and derived a new MAF table. I used Red Hard Supras Auto MAF calculator to derived my average Mass Air Flow for all given frequencies. Well since I have turned on my MAF with these new values the truck is running rich as hell. My Lt trims are on the average about -10. But why?

1) I increased the values in my maf table. so increasing it would tell the PCM that there is more air so therefore more fuel... am I correct?

2) I did my logging is SD mode, should I do it with the MAF on? And if so why should the logging be done with the MAF on. The way I see it you can tune it in SD mode.

3) why if I calibrated the MAF with these new values is it running really rich. I understand that if I tweak the values for the MAF I can bring it down to zeroes, but I see no reason in doing this.

CHarris

iTrader: (5)

If you get your tune very close in SD mode then the next step is to plug in/turn on the MAF and then log again. Logically, any error that you see with the MAF on is where your MAF table is not tuned right. Adjust the MAF table according to the log and you'll be correct. The truck will tell you what it wants. That's what you should give it.

02sierraz71_5.3

iTrader: (2)

I used supras sheet and had similar results. I made my tuning guide for the maf based off similar principales to what charris is talking about.

Check the sticky in the tuning section its got what you need

desTRUCKtive

Ok I understand you guys... but what I am thinking if your MAF is reading so many lb/min of air, those are the actual lb/of air that are entering the engine. Therefore, why would I tweak(mislead) the engine into thinking there is less air going in, just in order to adjust for the rich condition.

I know that you guys are right but doing this has got me thinking critical about this condition. And I am thinking there might be something else that could be adjusted.

What do you guys know abouyt IFR tables. Oh and what do they stand for.

CHarris

iTrader: (5)

You should think of the MAF like this... the numbers mean nothing. The frequency is a better gauge for comparison of air consumption. For example.... 12000hz could be in the 450 gram range (most trucks) or in the 480 range on another calibration (the stock H2 table is this way!). So.. clearly one cannot compare grams per second across platforms. But you can compare where one maxes the freq against another. Say one maxes the MAF at 12000hz at 5600 rpm where another may max the freq at 5300 rpms.

So... one can see that what the numbers are really doesn't matter. They wer adjusted by the factory to fit the application - to make it run right. You would just be tailoring yours to make your truck run perfect.

02sierraz71_5.3

iTrader: (2)

The maf is calibrated for the amount of air the engine takes in with stock components and of course when things are changed like intake, TB, big cam, ported heads it is going to change the amount of air and the way itacts. This is why the maf needs to be recalibrated to take advantage of the mods that have been made. If the maf did respond in a generic manner like your thinking then trims wouldnt be thrown off by modifications.

Thats my take on it, all I really know for sure though is that I was able to tune trims by changing the maf calibration table with the method Ive described in the sticky. I think there are advantages using the maf over just SD.

02Reaper

iTrader: (2)

I think this is all untrue. Trims are thrown off by modifications because the maf is calculating more air entering the engine and the computer is either adding or subtracing fuel based on its needs. Of course you can change the fuel the computer is adding or subtracting by modifying the maf calibration table, but the point is still being missed. If the maf had to be calibrated for every mod, then you would have to calibrate it for changes in the weather.

02sierraz71_5.3

iTrader: (2)

Your entitled to your opinion but the falisy here is the simple fact that trims are thrown off by mods and the factory calibration doesnt account for them. If the maf was adding the right amount of fuel with the factory table and mods then trims wouldnt be way out of whack.
The reason you dont have to account for changes in weather is because the maf works off of temperature.

If you need other proof greater than trims being off here it is; you need set you maf fail freq to 1 then set MAF High Freqency Fail Limit to 1. This will allow the maf to be used to read the air it thinks its recieving plus you will still be running in SD. It is important you have a completely tuned close to perfect VE table to do this. Notice the descrepancies in what the maf is reporting and the calculated air mass. You know the calculated air mass is correct because part of the equation is based off the ve table which you know to be true.

"The dynamic airmass calculations include various filters and strategies to predict the cylinder airmass from MAF, MAP, TPS, RPM, IAT and VE table inputs. "

We know that all the elements of the equation are true and the one that we are unsure of the maf has been eliminated but the iat is still being reported and the air intake is being read but not reported. This is why the maf needs to be recalibrated for mods it is not reporting the correct amount of air.

This is also why I outlined my tuning strategies for the maf the way I did and they work.

Granted this isnt an exact science and we are reverse engineering GM's software but this is the best way I have found so far to account for the discrepancies.

BTW Hpt 2.0 has a built in function for tuning the maf

1slowsilverado

iTrader: (1)

desTRUCKtive

I have not been able to figure the built in function for the MAF Calibration, maybe I should try this. How do you do this and if possible can you outline an explanation.