Cobra intake and injectors in GT

[Adam95GT]

nobody was pointing fingers its just that we were talking about the "Some People" stating that the cobra's ecu accounts for the 24's i think its odd that a 24 cal'd maf would even be on a cobra...

 

[final5-0]

I got a bit more time now to talk about this stuff

Lets back up to the beginning

Lets look at this from the perspective of the aftermarket meter folk
which in this case is ProM

or maybe is PMAS
or whatever they call themlelves these days

Maybe some of you have seen peeps talk about the ... Cheat Method
of calibrating a meter which the aftermarket folk started

I know ... I mean ... You gotta know by now :Word:

You have seen myself and others repeat over and over

OEM Ford meters are not caled for any particular size of inj

I'm a gonna try and tie all this stuff together

Most likely JT, Greg, Wes, or some other member
is gonna have to bail me out on this one
BUT
I'm gonna strive to keep it very basic and simple with this post

Of course ... we can talk more later

One last warning
It will be simple
It will be kept very basic
BUT ... It will be a bit long as it is a good bit of info to deal with

We are gonna look at 94-95 applications only here folks :Word:
just know this
Fox folk don't have to deal with the same issues
therefore
Most of the fox meter/inj talk does not apply to us 94-95 folk

Also ... AFPR's/elevated fuel pressure will N O T be present here

Main topics we are gonna deal with will be ............
1) OEM GT meter application
2) OEM Cobra meter application
3) Aftermarket meter manufacture ... Cheat Method
4) A bit of injector size application

btw ... A fairly simple but good article can be found on my site about the C M
if anyone wants to get all the details

1&2 First ... We all know it is the exact same meter on both cars
yet
GT has 19's and the Cobra has 24's

Meters measure air ... Plain and Simple
Aftermarket meter folk make peep think fuel is in the mix as well

A stock GT will generate only so much airflow
and
A stock Cobra will generate that much and a bit more

If you grasp that fact, then consider the additional amount of airflow of
the Cobra is not enough to render the meter ineffective

That is all there is to that ... no need to talk any more
except to say
That is why the exact same meter works just dandy for both cars

Now ... We can't run on airflow only We gotta have a bit of fuel

4) Injector size requirements are not the same for both cars

It ain't Rocket Science my gearhead friends

Cobra makes more power and needs more fuel

R E M E M B E R ... we are talking 39 pounds of fuel pressure here
therefore
Don't be mislead by the OLD SCHOOL FOX mechanical tuning method

Honestly ... If hosing around with fuel pressure was the Bees Knees

Don't ya think we would'a seen Ford equip our cars with AFPR's

OK #3 ... Last Topic of discussion

Is anyone still reading this novel

The Aftermarket Meter Folk know and depend upon several facts

a) They know info about OEM meter capibilities
b) They know info about the size of inj used on the car
c) They know how much airflow is generated by how much hp
d) Most important of all They know about OEM pcm parameters :Word:

They use what is called the Cheat Method to try and make things so
you don't have to go inside the pcm and change things when you
want to use one of their meters

You gotta know this was first done with the older Fox Stangs

Worked fairly good for them boys for years
Unfortunately ... Works not so good for us

We won't go there but its all about our pcm's being load based
and
The older Fox pcm's are focused around rpm

Now ... Say you have modded your Stang beyond what the tiny OEM
19's can safely deliver fuel at ... OEM ... or 39#'s of pressure

Again ... you don't have pcm access
therefore
Even though the meter will handle the additional airflfow .....

You need larger injectors
so
You get a meter from ProM ... Calibrated (Cheat Method) ... for larger inj's

The Cheating part is ...........
They lie or tell a fib to the pcm about how much airflow is really flowing
through the meter

A simple way of looking at it might be

We got 2 Stangs we will use for example only

One has 200rwhp, 20# inj's, moves 500 kg of airflow, OEM pcm

The other is being built and its owner estimates it wil make about
300rwhp and wants to avoid a custom tune

He calls ProM and they base their findings off these facts ...
PCM THINKS he has 20's and can move a maximun of 500 kg airflow
ProM knows he might REALLY generate around 1000 kg of airflow
They reccomend him to use 40# injectors to safely allocate enough fuel
They rig up the meter to report 1/2 or 50% of actual airflow

Are you starting to see how things are working out here

Inj's are twice as big as the pcm thinks
but
Meter only reports half of the REAL airflfow to the pcm

therefore

The pcm commands a smaller pulsewidth due to the lie the aftermartket
meter boys setup in the meter to account for the larger size inj's

Well ... There it is my friends

btw ...You most likely have seen the folk who have access to the pcm
talk about the maf transfer curve

In a nutshell
Thats where they tell the pcm the ... TRUTH ... about generated airflow :Word:
AND
They tell the pcm it no longer has those tiny 19's

Man O Man ... I'm done for now

I either helped or made it clear as mudd

Ask away if needed and I will try to help
or
Maybe someone can fix my messed up attempt to splain this stuff

Grady

 

[humphrey111]

phew...i'm exhausted....

 

[95_cobra123]

WOW..... do you have a keyboard left after that one Grady?

 

[final5-0]

phew...i'm exhausted....

Did you see anything that made sense or helped you out

Grady