Pegging the MAF?

You have it. ALL the MAF is for is measuring air volume going into the motor. Period. Forgot all that brainwashing we've been put through (I thank the tuning crowd like Grady and Vristang for helping to undo these misconceptions).

The scale is indeed 5 volts. This is done because it's stable. If your battery is half dead or you have voltage fluctuations at idle vs at speed (our volts drop at idle), the 5 volt reference system all but eliminates concerns about fluctuation-induced changes.

Injectors are a different animal. We actually like to see them have a high duty cycle (running near max). If they ran non-stop, that'd be 100% duty cycle. The injectors get constant (accessory) 12 volts and drivers in the puter ground each one when it needs to introduce fuel.

Not to nitpick (but here I go anyway.. LOL!) but the MAF measures air mass - in other words - weight. By doing this atmospheric pressure and temperature changes are automatically compensated.

The other thing is the MAF limit from the factory is actually around 4.7v. A tune can extend that to 5v to allow a little more headroom.

Acutally, 'calibrated' MAFs will peg later if they are calibrated for larger injector sizes. e.g., a MAF calbrated for 24# injectors will peg much sooner than a MAF calibrated for 42# injectors. Since factory MAFs are not calibrated for any injector size that really doesn't apply to them - sort of - because the MAFs on '03-04 Cobras and Gen 2 Lightnings will peg a lot later than one from a 94-95 GT.
Hope this helps.
Don

The "calibrated" MAF idea is only in a global change in the airflow vs voltage out for the sensor. To "calibrate" the MAF really just means to add or subtract voltage at the output. It's all in tricking the computer to calculate the injector PW properly. I say "calibrated" because in reality, it's a hack.

igotyofire said:

Im having a lil debate with someone and was wondering is a Maf's limit based on the injector size its calibrated for or airflow? i saw a thread by Grady earlier discussing a little on this. i can understand the injectors themselves being pegged, but i cant see a Maf pegging unless its flowing its max amount of air. It seems like the bigger the maf used the more air it can flow before allowing itself sensor to be pegged since according to grady's thread about tunning them the voltage doesn't go past 5volts? which is how ive come upon to this conclusion. Im sure Grady will be here to chime in some more,lol

thread im refering too http://forums.stangnet.com/showthread.php?t=701539&highlight=mass+airflow

Click to expand...

Well

Some pretty smart folks have given you good info IMHO

Did you get the answers you needed to satisfy your concerns

Grady

Seems like you might be getting side tracked by physical meter size

Sticking with an electronic caled meter such as ProM and the like ...

The meters are setup to measure airflow :Word:

The amount of airflow determines the size inj necessary to feed that airflow.

Focus on the electronics and not the physical size of the meter

Example:

You could have two 80mm ProM meters ........
one with a 19# cal
and
one with a 42# cal

The physical part of each meter is the same
but
The electronics are very different

Lastly ... each meter M U S T work within a 0 to 5.0 volt range

Now you have two choices of application with these meters
1) Use the after market cheat method of matching meter/inj size calibration
2) Use a tuning interface or chip to tell the pcm true airflow & inj size

#2 will usually provide more accurate results

Grady