WOT On/Off Shifting Hesitation

[2K3SVT4ME]

Ok well I took my termy to the track for the first time on Saturday and was all pumped up and ready to go. I didnt drive the crap outta the car at all, in fact i went down on non drag radials walked the car out got 1 .95 60ft nailed the throttle went for second car momentarily hickups then goes like normal, go for third does the same, go for 4th does the same.....Im just granny shifting and doing WOT On/Off throttle shifting every gear I mash the throttle in it gives me a momentary hickup....i was told it could be pprv so i did that tested the car afterwards and still does it, put in a new set of plugs thinking they could be fouled still does it......what do i check next? heres the thing if im in a gear and mash the throttle the car pulls through the gear no problem its just when i go wide open throttle then come off the throttle shift and mash it again when i mash it again it hickups then gives me full power.....any suggestions or help would be great....its a KB 2.2L with stock fuel pump and KB BAP,55lb injectors,JLT cold air kit,billet flow t-body MAFIA and predator tuner......any suggestions?

 

[kirks5oh]

did you remove the PPRV, and upgrade the fuel hoses?? its not entirely clear in your post. i had the EXACT same problem you have, and deleting the PPRV worked like a charm. make sure you get a FRPS washer from kenne bell to prevent blowing the FRPS.

i've also heard that it is correctible in the tune--

particularly if you run the predator. some people with the SCT tuners were not able to get rid of it even with extensive tuning

 

[2K3SVT4ME]

pprv

did the pprv delete and changed plugs but thats the extent of it and it still does the exact same thing. its pretty bad considering i can do 30-40mph roll ons but when i mash it and then quick shift it hickups. what can be done in the tune to prevent this? frps is the fuel rail pressure sensor right? should this be changed? I just dont want to get into spending needless money like i have so far, doing the pprv delete did absolutely nothing and im wondering if its another issue altogether but from my research all i can figure out is pprv and or retune.....should the car be retuned after pprv is done?

 

[04sleeper]

Welcome to the world of the "Returnless" fuel system.

There are very few things that you can do unfortunately. You can clip the FRPS max to around 58-60 PSI, and try to dial in the fuel pump voltage table to match what is commanded.

Another thing that can help is to upgrade to a bigger feed line like a -8. This way it still has some volume to pull from.

Here's a good explanation of what causes it.

Now when you are at WOT, the PID controller is adding voltage to the fuel pump because you have done some kind of mod to the vehicle that now requires more fuel. Great, it’s keeping the pressure drop where it should be. But when you go to shift, the fuel demand drops when you are shifting. But the PID controller is still adding voltage. So what happens? Fuel pressure responds by spiking high because the fuel flow from the table is much closer to what it needs to be at lower fuel flows and the controller is still adding voltage. The PID controller sees that error and goes after it. So it starts to back off fuel pump voltage in a big way. Right here there is a flaw in the Ford control logic. There is no max or min clip for any of the terms in the fuel pump PID controller. So the controller starts taking away voltage to bring the pressure down. But now you push on the pedal because you want power. The injectors open up trying to give you more fuel, but the PID controller has taken all the voltage away and it can’t respond fast enough. So you have no fuel pressure.

Now, if you had made the voltage table accurate, where it had the correct voltage for high fuel flows, the PID controller would not have to add the voltage in to make up the difference, so it wouldn’t be adding voltage when the fuel flow dropped and you would have not gotten into the overshoot/undershoot situation.

 

[04sleeper]

The BEST way to get rid of it for good is to go with a return setup like the one from Lethal Performance. Then there will be NO fuel spikes.

That is what I am going with.

http://www.lethalperformance.com/pa...nce-03-04-cobra-return-style-fuel-system.html

 

[2K3SVT4ME]

........

Im just wondering why everyone doesnt have this problem? is it all about what setup you run or luck of the draw?

 

[04sleeper]

Im just wondering why everyone doesnt have this problem? is it all about what setup you run or luck of the draw?

Everyone Does have this problem to an extent. It's called a returnless fuel system.

Some don't experience it as bad as others depending on their set ups. Also, if you shift faster then you won't experience it as much either.

 

[john3883]

i just got the car back on the 22nd of sept. first thing i noticed was the stall/hesitation between shifts. tuner said give it time. i have given it week and half and lots of miles. still got it. I am in the same boat man. if i do a return style fuel system is it a promise i will have no more probelms and be set for the KB?

 

[SciFiHiFi]

Some don't experience it as bad as others depending on their set ups. Also, if you shift faster then you won't experience it as much either.

Agreed. I'm too lazy to delete the PPRV so I sloved the problem using my right foot.

 

[2K3SVT4ME]

video

here is a video of our local drag day, i just brought the car in street trim running non drag radials and powershifting was out of the question on regular street tires.....scroll in to 3 min. 27.sec thats my ride in the right lane, you can hear me walk the car out and granny shift but you really hear the baboom between shifts....

[ame="http://www.youtube.com/watch?v=QLSmdjmCSoM"]http://www.youtube.com/watch?v=QLSmdjmCSoM[/ame]

 

[04sleeper]

i just got the car back on the 22nd of sept. first thing i noticed was the stall/hesitation between shifts. tuner said give it time. i have given it week and half and lots of miles. still got it. I am in the same boat man. if i do a return style fuel system is it a promise i will have no more probelms and be set for the KB?

You should be fine if you go with a return style set up. The fuel is always there at the rails. :thumbsup:

 

[gx00850]

I had the EXACT same problem. I was going to do the pprv delete. I installed a modified FPDM (stage 2) and problem was gone. I did not have to do the pprv delete. You might want to give that a try before you spend too much money in changing the fuel system. Good Luck!

 

[2K3SVT4ME]

Pleasr excuse my lack of knowledge but what exactly is the FPDM and what is its function? I'm all for not swapping out the fuel system for another so anything helps. Its pretty bad in the video and I don't want to have to live with it either and am hoping for a fairly cheap fix if possible!

 

[image]

As much as i hate to admit it, power shifting solves the problem.,. Mine used t hiccup until i kept the pedal to the floor the whole time. :beer:

 

[2K3SVT4ME]

stage 2

I had the EXACT same problem. I was going to do the pprv delete. I installed a modified FPDM (stage 2) and problem was gone. I did not have to do the pprv delete. You might want to give that a try before you spend too much money in changing the fuel system. Good Luck!

Where do you get a modified stage 2 version? Would replacing the stock one with a new stock one help or is the stage 2 version different altogether? Any help would be great. I figured out what FPDM is Fuel Pump Driver Module...LOL!

 

[04sleeper]

Changing the FPDM Is not going to fix the fuel pressure from having spikes.

It is the whole reason why the car hessitates.

You can "help" the issue be not quite as bad by tweaking the tune, but the problem will still be there. The datalog will show the variance.

 

[AC Mech]

fwiw, I had this annoying issue and it was able to be resolved in the tune. Good luck.

 

[2K3SVT4ME]

.....

fwiw, I had this annoying issue and it was able to be resolved in the tune. Good luck.

what specifically did you have to have done with your tune to get rid of it?

 

[04sleeper]

fwiw, I had this annoying issue and it was able to be resolved in the tune. Good luck.

It may "Feel" resolved in your right foot, but it still there. Datalog it and you will see. :read:

what specifically did you have to have done with your tune to get rid of it?

See post 4 above.

 

[thomas91169]

As much as i hate to admit it, power shifting solves the problem.,. Mine used t hiccup until i kept the pedal to the floor the whole time. :beer:

I actually adjusted when i put my foot back into the throttle. Used to do them in tandem, just as im clutching out im getting into the gas again. Now ill get back into the gas just as im getting ready to clutch out, so when i do clutch out, im taching up already and that shift chug/hesitation is no longer an issue, or at least one that can be felt. it probably still happens but there is either little to no load on it at that point since i will just be barely clutching out at that point, so it wouldnt be felt through the entire car and into the butt datalogger.