The Aluminum housing & electronics module or the complete meter is the same no matter if Ford put it on a GT or Cobra. Its the curve in the pcm of each car thats a bit different as you have pointed out here.
Ford could do that since neither motor required more air than the meter could accurately report to the pcm.
The most obvious difference is the size of inj's and Ford just made that made known in the Cobra pcm.
Different heads and intake made some adjustments in the transfer curve necessary.
After you add up all the differences, the curve will need a bit of tweecing and you see it as Ford did it in the difference between the two curves.
There is nothing sacred or taboo as far as adjusting the maf curve if it is needed. Here are a few examples where a slight adjustment might be needed.
1) Say you put a small cam
or
2) headers/mid-pipe/catback in a cobra
You most likely could use a bit of transfer curve tweecing at or around idle for optimum drivability.
3) Say you get a wb and make your first wot, max rpm baseline test run.
You are gonna find the high end fat as that is how Ford set it up.
A bit of maf curve tweecing may be needed to take care of that.
Now then, does any of the above give you ideas that allows you to answer your own Q
btw ... mafs/inj's were one of the hardest things for me to get my head around and I had to work at it a good bit until I started to see the light.
In the same line of thought, why is the low and high slope the same on the J4J1 file. From myn reading different sources, most suggest low to be 1.2x high. What is better same or different.
I have a question grady, I didnot receive my pmas maf yet. When I take my car out and load up the J4J1 file, should I use my stock MAF transfer or the cobra one. I hope to get it this week but it will not happen I think.
In the same line of thought, why is the low and high slope the same on the J4J1 file. From myn reading different sources, most suggest low to be 1.2x high. What is better same or different.
I messed around with all those inj parameters years ago before Clint came out with his EA program. It was an Excell file from the first guy that came up with a system to help dial in your inj's with EEC Tuner, Tweecer, and the like. It was not user friendly like EA btw
Won't go into all the detalis but ....................
You can get a good, stable CL tune with the slopes ................
the same
OR
low 1.1 X high
OR
low 1.2 X high
OR
low 1.5 X high
Its all about using different break points, offsets, maf values, and such. A general rule of thumb is:
The lower the offsets the closer the slope values
As for the differences in the t4m0 & j4j1 there is a story that has been passed around for ever but I don't know if its true. If true, it could explain some of those differences.
Roush and his team were responsible for the j4j1 and they had a pressing deadline so that is why you see some of the adders zeroed out and slopes the same thus making the breakpoint void. The consensus seems to be the file was a fast & nasty and they just hit the high spots.
That being said, in my way of thinking, the j4j1 does address the weak points of the t4m0 if talking about na combos.
For what it is worth, my file is kinda sorta a cross between the two as far as inj values go. It just kinda worked out that way
If I was gonna start off form scratch with a h/c/i combo, I'd follow pretty closely the info you find in EA.
I have a question grady, I didnot receive my pmas maf yet. When I take my car out and load up the J4J1 file, should I use my stock MAF transfer or the cobra one. I hope to get it this week but it will not happen I think.
Just send me yours, I just wanted to get the gist of how it was done. I was gonna come up with a user friendly spreadsheet. Check your PM's for my email address