Defuels at throttle toe in

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FordRacing200

New member
I have a 04 lb7 with California emissions, it's straight piped, intake, boost valve, efi live tuned with stock transmission tunes, and I'd I jump right on the throttle from a Roll it Defuels hard for a Second then comes back alive.... Do I need a lift pump or is it just defueling for a downshift??
 
I'm not familiar with the cts setup.

Commanded rail psi would be dependent on your tuning. To log it you're looking at commanded vs actual. I don't have the metric numbers off the top of my head, but max commanded on an LB7 is 24K psi. The actual would be dependent on the tune's pulse width.

Basically in this case, your looking for a big drop in rail psi at high throttle percentage.
 
The defuel is due to the "clutch-on clutch-off" design of the Ally. It is there to prevent tie-ups when it shifts.

You can turn off defuel, however it is not recommended. I wouldn't advise it.
 
WhitetailAddict said:
The defuel is due to the "clutch-on clutch-off" design of the Ally. It is there to prevent tie-ups when it shifts.

You can turn off defuel, however it is not recommended. I wouldn't advise it.
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Just curious..What is the fix for this? I don't think we ever really ironed it out. *this was a long time ago* Transgo? TCM tuning?
 
fordcummins01 said:
Just curious..What is the fix for this? I don't think we ever really ironed it out. *this was a long time ago* Transgo? TCM tuning?
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I'm not quite sure what you're asking. The defuel is there to prevent tie-ups while shifting. It's the nature of the Ally so-to-speak.
Like I said, it can be turned off in the tcm.

To the op, I forgot to mention before, you may have been experiencing the adaptive learning. If that style of driving was abnormal, the trans is unsure how to shift and will shift lazy.
 
since you don't have a lift pump in your sig. try changing your fuel filter. When you jump in the throttle it sucks in a big gulp of fuel and a dirty fuel filter can make the lines run dry for a split second(long enough for the truck to studder or fall on its face) then take off again. I see this on stock trucks that we put a race tune on from time to time.
 
after re-reading the original post, does it do the same from a dead standstill or just on the downshift?
 
Due to how the ALLISON shifts, it must defuel on a downshift like this. The ALLISON must go through every gear when it downshifts, so if your cruising in 5th and kick it it must go down to 4th then 3rd before it can bring the fuel back in and take-off. It is the natre of the beast.
 
FordRacing200 said:
Just from a roll, but it like goes dead for a moment. The fuel filter has 9k miles maybe 5 months on it, less I think.
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Your fuel filter is ready for a change.. Usually 10k is the life of them. One tank of not so good fuel will kill them too. Put a new filter on and try it.
 
Ohhh makes sense. And yeah I'm changing my filter later today. Gosh how I love the location of it... It makes it so easy to take a bath in diesel fuel and be pissed off for 24 hours
 
I think they make an extension bracket to help with changing it. (also a billet insert in the filter instead of the cheap plastic one..) Drain it first..you'll be a lot happier.
 
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