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?
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
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
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
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.
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.
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