Question regarding J4J1 computer

[nmcgrawj]

What would happen if you ran a cobra computer with a stock MAF and 19lb injectors? Would you run lean all the time? How would it be in the upper RPMs?

 

[rj95svt]

It would run a bit lean and probably not very good overall. I would wait till you have 24lb injectors before putting in the j4j1.

 

[nmcgrawj]

Well I dont have a computer now.

I guess my question is a cobra computer better to start with Tuning wise? I won't be tuning immediately. But since I have to buy a computer I wanted to get the best one. Even if that means finding 24lb injectors...

 

[nmcgrawj]

and doesnt the stock tune run rich in high rpms? Would it be too lean? Or no way to tell exactly how much?

 

[final5-0]

You got your answer

I am one of those ... Why ... kinda guys

Think along these lines and you will see ... WHY

The meter makes no nevermind as we all know the GT and Cobra use
the exact same meter

If you use 19's with the j4j1 (Cobra pcm) and no pcm changes

The pcm has no knowledge of the smaller inj's so it will be making decisions
and commanding smaller size injectors to pulse a certain amount which will
obviously be a smaller amount thus ... lean city

Sure ... You can bet Ford is gonna setup the fuel to be fatter as the rpm's
climb cause more rpm is more load thus more fuel is needed as the motor
is doing more work.

Yes ... the j4j1 can be a good starting point or foundation to build a tune
upon if one has more than bolt-ons.

Grady

 

[legalize420]

while were on this subject i wanted to ask if running the j4j1 tune with stock injectors would you set the slopes the same high/low 19/19, or high/ low=high *1.33( i think that was the number in BE) 19/25.27? i just registed BE and EA so i will start messing with those over the next few weeks. im going to get a set of 24's soon but for now im still on the 19's so which slopes would you use?

 

[nmcgrawj]

You got your answer

I am one of those ... Why ... kinda guys

Think along these lines and you will see ... WHY

The meter makes no nevermind as we all know the GT and Cobra use
the exact same meter

If you use 19's with the j4j1 (Cobra pcm) and no pcm changes

The pcm has no knowledge of the smaller inj's so it will be making decisions
and commanding smaller size injectors to pulse a certain amount which will
obviously be a smaller amount thus ... lean city

Sure ... You can bet Ford is gonna setup the fuel to be fatter as the rpm's
climb cause more rpm is more load thus more fuel is needed as the motor
is doing more work.

Yes ... the j4j1 can be a good starting point or foundation to build a tune
upon if one has more than bolt-ons.

Grady

Ha grady i've missed your long responses!!!!

I gotcha. So here is my next question, would it serve me any benefit to get the J4J1 now and also get 24lb injectors, rather than just getting another GT computer and keeping my current 19lb injectors? Untuned, which setup is better in your opinion?

BTW, i will be running an explorer intake, gt40p heads, and a custom cam from ED for a turbo setup, but it ran pretty hard n/a before the accident.

 

[blksn955.o]

If your going turbo and dont have the 24's I would just get a GT computer. You will have to get bigger inj. with the turbo so you will be buying 2 sets of inj.

If you have 24's just laying around...why not everything will just plug and play at that point.

The GT eec can take the cobra eec base tune if you run a tweecer. The Cobra eec is a little bit easier to tune with due to some items deep in the programming being "off" IIRC.

 

[final5-0]

while were on this subject i wanted to ask if running the j4j1 tune with stock injectors would you set the slopes the same high/low 19/19, or high/ low=high *1.33( i think that was the number in BE) 19/25.27? i just registed BE and EA so i will start messing with those over the next few weeks. im going to get a set of 24's soon but for now im still on the 19's so which slopes would you use?

A Very Good Question ... Indeed it is Sir

My opinion about the difference in how the t4m0 & j4j1 pcm's are setup is
W A Y more involved than just inj slope size values.

Yes ... the t4m0 has a low slope value of about 1.2 times the amount of the
high slope and the j4j1 have equal values for the slopes.

The battery offsets of each pcm are VERY different and I found that makes
a BIG difference.

I played around with slope values the same and with a difference between
them as great as 1.5 times the amounts.

You end up using smaller or greater offsets depending on slope values you
choose.

I spent a good bit of time looking at the differences between the t4m0 & j4j1
so I guess you could say after a while I kinda saw some trends in each pcm.

You also have to deal with the breakpoint as well which will add one more
variable into the mix

I found I could get a stable tune either way with the slopes
and
I ended up kinda using values that was a bit of both pcm's

I think I'd stay with the t4m0 if you are using 19's

If you wanna try the j4j1 with 19's ... you could start with t4m0 slope, battery
offsets, and breakpoint values as a starting point

Just my thoughts but Wes and others may have differnet ideas as
I did most of my tuning a good while back there before all the
new help programs were around


Grady

 

[nmcgrawj]

Well i wasnt going to go turbo immediately....it wont happen in 08. The other thing i might do is run a PMS again....so i wouldnt have the ability to load the J4J1 calibration if i got a GT computer.


I am probably splitting hairs....the car ran fine before with the GT computer and 19s.

 

[legalize420]

A Very Good Question ... Indeed it is Sir

My opinion about the difference in how the t4m0 & j4j1 pcm's are setup is
W A Y more involved than just inj slope size values.

Yes ... the t4m0 has a low slope value of about 1.2 times the amount of the
high slope and the j4j1 have equal values for the slopes.

The battery offsets of each pcm are VERY different and I found that makes
a BIG difference.

I played around with slope values the same and with a difference between
them as great as 1.5 times the amounts.

You end up using smaller or greater offsets depending on slope values you
choose.

I spent a good bit of time looking at the differences between the t4m0 & j4j1
so I guess you could say after a while I kinda saw some trends in each pcm.

You also have to deal with the breakpoint as well which will add one more
variable into the mix

I found I could get a stable tune either way with the slopes
and
I ended up kinda using values that was a bit of both pcm's

I think I'd stay with the t4m0 if you are using 19's

If you wanna try the j4j1 with 19's ... you could start with t4m0 slope, battery
offsets, and breakpoint values as a starting point

Just my thoughts but Wes and others may have differnet ideas as
I did most of my tuning a good while back there before all the
new help programs were around


Grady

well i still have a lot more to learn but for now i am having better results with the j4j1. the car will idle and run good with either tune but i have the hot start surge and die problem with the t4mo. i will try a j4j1 tune with the t4mo slope, offset, and breakpoint and see how that works out. for now 19/19 seems to be working so i might not mess with it too much until i get the 24's. thanks

 

[Stanger007]

while were on this subject i wanted to ask if running the j4j1 tune with stock injectors would you set the slopes the same high/low 19/19, or high/ low=high *1.33( i think that was the number in BE) 19/25.27? i just registed BE and EA so i will start messing with those over the next few weeks. im going to get a set of 24's soon but for now im still on the 19's so which slopes would you use?

I would keep the stock slopes - there are a few other areas tied into the slopes you use like Grady mentioned. If you can beg/borrow/steal a wideband and can datalog I can show you how to dial in your combo very quickly.

I'm not a fan personally of using the same high/low slopes - I know there are several ways to skin a cat but if you look at other stock Ford programs, they are always setup with different high/low slopes. It has been thrown about that the tuning for the Cobra took place in an abbreviated timeframe and the slopes were left the same for time reasons. I do not know the truth of this but I can speak from experience on what I've found to work across many cars.

As you move up in injectors, look at the template files I have on Welcome - [tunexchange: Better tunes, less fat]. These injector templates are proven to get you where you need to be without the guesswork.

Lastly (this is extra credit), to see what Ford has to say about how slopes etc change in various injectors based on fuel pressure etc, look at the "Calibration Summary" items on this page: Ford Racing Performance Parts [M-9593-LU60*]

my 2c,
Wes

 

[legalize420]

I would keep the stock slopes - there are a few other areas tied into the slopes you use like Grady mentioned. If you can beg/borrow/steal a wideband and can datalog I can show you how to dial in your combo very quickly.

I'm not a fan personally of using the same high/low slopes - I know there are several ways to skin a cat but if you look at other stock Ford programs, they are always setup with different high/low slopes. It has been thrown about that the tuning for the Cobra took place in an abbreviated timeframe and the slopes were left the same for time reasons. I do not know the truth of this but I can speak from experience on what I've found to work across many cars.

As you move up in injectors, look at the template files I have on Welcome - [tunexchange: Better tunes, less fat]. These injector templates are proven to get you where you need to be without the guesswork.

Lastly (this is extra credit), to see what Ford has to say about how slopes etc change in various injectors based on fuel pressure etc, look at the "Calibration Summary" items on this page: Ford Racing Performance Parts [M-9593-LU60*]

my 2c,
Wes

i will be getting a wideband soon so if i still need some help i will let you know. i loaded up a tune with the t4m0 slopes, breakpoint, and battery offset as grady suggested. i took a look at the template you have on your site for the 19's and the only thing i have different is FN348A, cranking PW vs. ECT. any idea what is different about the two (j4j1 and t4m0) that would cause hot start surge problems? fuel, spark, both? thats really the only reason why im running the j4j1 now. i have 2 different tunes loaded in that i know are working for now so im just going to give it a few weeks until i get the 24's and the wideband before i start trying to fine tune it.

 

[Stanger007]

any idea what is different about the two (j4j1 and t4m0) that would cause hot start surge problems? fuel, spark, both? thats really the only reason why im running the j4j1 now.

The hot start is likely one of two problems (datalog with wideband will tell me for sure).

Try putting all 0's in the table FN1361 as a test to see if your hot start issue is changed.

How is your idle and transition from cruise to idle otherwise?

Wes

 

[final5-0]

I'm not that well versed in the newer software so I can't tell you exactly where
to look for hot start issues

I will tell you that where ever you see the cranking table which involves
temp, time, and ... IIRC ... an adder to the normal fuel ratio ...........
that might be a good place to dial back some fuel

Seems like as time or temp or both increase ................
The adder gets smaller and smaller but I don't exactly remember

I switched to a different pc and don't have my tuner stuff loaded anymore
so I can't quickly look it up

Not much help I know ... but ... Good Luck

Grady

 

[final5-0]

Ha grady i've missed your long responses!!!!

I gotcha. So here is my next question, would it serve me any benefit to get the J4J1 now and also get 24lb injectors, rather than just getting another GT computer and keeping my current 19lb injectors? Untuned, which setup is better in your opinion?

BTW, i will be running an explorer intake, gt40p heads, and a custom cam from ED for a turbo setup, but it ran pretty hard n/a before the accident.

I had you a reply ... almost ... ready to go the other night
but
We suddenly lost power so the reply I had for you was lost as well

Untuned ... most peeps will tell you the t4m0 usually makes a bit more power

I found the same results when I ran an older combo with self ported heads,
OEM intake with a bit of port work as well, & yada yada yada.

When I loaded in the j4j1 file I realized a loss in power

however ......

A bit of sparking & fueling tweecs to the j4j1 file and not only did I find
the missing power ... I surpassed it by a bit too.

btw ... We are not talking about big differences
but
differences that were big enough to be noticed

Main thing is not to exceed the fuel requiremints of those tiny 19's

Peeps just don't know how small they really are :Word:
especially
When you work em at the OEM fuel pressure

Grady

 

[legalize420]

The hot start is likely one of two problems (datalog with wideband will tell me for sure).

Try putting all 0's in the table FN1361 as a test to see if your hot start issue is changed.

How is your idle and transition from cruise to idle otherwise?

Wes

ok. i set up a t4m0 tune with all zeros in FN1361. i will let you know later on today how that works out . i guess that brings me to my next question about idle? should it stay rock solid at one number or is it going to flucuate slightly no matter what. i have not even started to use EEC analyzer for the maf and tb air flow yet so in the next few days i will see if that helps. otherwise the stock tach looks like it stays in pretty much the same spot at idle but in the logs i see it moving a little bit up and down. transition from cruise to idle is pretty smooth. it will hang at about 1100 rpms and then come down when i stop so i think thats working ok.

 

[Stanger007]

The idle should not surge up and down if the tune is correct. The ISC tool in EA will walk you through recalculating what needs to be calculated to make it rock solid, check the Help button, it will explain it better than I can.

The idle should briefly hang until you get below 7ish mph (it varies per car depending on VSS/learned VSS settings). It should not hang long. Again, the ISC tool will also help with this.

Wes