ride4lyfe

i have located my bad injector, ford wants $156 for a single 19 lb injector so i figured im gonna just go ahead and get the 24 lbs injectors from american muscle. Will i need to recalibrate the MAF, and the car is going to get tuned after the injecotors go in. The car has tb/plenum/typhoon intake manifold/ JLT CAI/ LT's/ OR H/ Cat bac/ UDP's/ alm drive shaft and 3:73's

H0SS302

you wont need to recal the MAF, the tune SHOULD take care of that. As long as your tuner is using computer based software and not just using the handheld you should be ok.

I would recommend buying some 19#s off ebay. 24s are a bit much for your application.

ride4lyfe

the last tune i had was from johnny lightning performance(jlp) and he tuned the car using my predator... my dumb *** cleared the predator and no longer have the tune he sent me...that being said will i need to worry about the MAF calibration?

cliffyk

Other than the silly after market MAFs made to trick specific stock tunes into working with higher capacity injectors, MAFs are not "calibrated" for specific injector sizes.

They do have a transfer function however which when loaded in to the tune lets the PCM calculate the mass ait flow based on the MAF's output voltage. Once that transfer function has been loaded in to the tune it does not normally have to be altered.

What will need to be done however, will be to re-program the low and high injector slope values to reflect the new 24 lb/h injectors--if this is not done the engione will run quite rich...

ride4lyfe

and this can be done with a tune correct?

ShadowDrake

+1

MAF "calibration" is just a method used to trick the ECU. The MAF reports a voltage, the ECU turns that voltage into a known mass of air (it uses a function to do this). It uses that information, combined with the injector size, to know how long to hold the injector open to achieve a correct air/fuel ratio.

When you change injector sizes, say, from 21 to 42... 5ms of open time on a 42 lb injector will result in 2x the amount of fuel that 5ms of open time on a 21 lb injector. A MAF "calibrated" for a 42 lb injector will only report HALF the amount of airflow otherwise. The ECU thinks there's half the air, so it only keeps the injector open 2.5ms instead of 5, resulting in the proper A/F ratio again.

Since 96 or so though, the A/F ratio calculation isn't as simple as it was in the earlier EFI mustangs, where a simple calibrated MAF is enough to do it. There's modifiers in the ECU which change the pulse width by a set time instead of a percentage, so while adding 3ms to a calculated pulse width would be ok on stock injectors, a changed MAF will not adjust that 3ms adder... you'll end up with A/F ratios that are still off with a calibrated MAF, and probably even a hard time starting (as fuel startup is often based on ECT/ACT and IAT, NOT the MAF voltage!)

Don't get a calibrated MAF. Wait to do the swap till you can get the tune adjusted for the new injectors.

Or just buy the stuff to tune it yourself like I have

massred98gt

spare yourself alot of time and money and go to a pull it yourself junk yard and pull a couple injectors off a crownvic/towncar/thunderbird/mustang etc. problem solved. no need for larger injectors until you start getting in to bigger cams or F/I