Hesitation in boost and high rpm

[StealBlueSho]

I thought you said at lower rpms? I am confused... so I am guessing that a 0-60 pull is when you still have issues? Maybe I am misunderstanding?

[polskifacet]

I thought you said at lower rpms? I am confused... so I am guessing that a 0-60 pull is when you still have issues? Maybe I am misunderstanding?

0-60 or pretty much any time it downshifts @ WOT

[ZSHO]

Did you ever check the LPFP ?.Z

[StealBlueSho]

And LMS said to not worry about the drop in FP and accompanying hesitation?

[polskifacet]

Did you ever check the LPFP ?.Z

From what I understand LMS put a fuel pressure gauge on it and ran it on the dyno, came out ok.

[polskifacet]

And LMS said to not worry about the drop in FP and accompanying hesitation?

Yes this is what they said.

[StealBlueSho]

And LMS said to not worry about the drop in FP and accompanying hesitation?

Yes this is what they said.

That is phenomenal.... did you ever monitor your STFT when this hesitation occurred? I can mail you out my spare HPFP to test a different fuel pump if you want... I would like it back though.

[polskifacet]

And LMS said to not worry about the drop in FP and accompanying hesitation?

Yes this is what they said.

That is phenomenal.... did you ever monitor your STFT when this hesitation occurred? I can mail you out my spare HPFP to test a different fuel pump if you want... I would like it back though.

After experiencing the hesitation I was fairly pissed as I would have expected them to just turn down my tune until they find the root cause. I am on my second HPFP as it came with the long block but thanks for the offer bud. Logging with AJP the STFT were ok.

[StealBlueSho]

Hmmm... how low was your fuel rail pressure getting, do you remember? I have had mine drop to 800psi before and it hesitated/shuddered until the pressure came back up.

[polskifacet]

Hmmm... how low was your fuel rail pressure getting, do you remember? I have had mine drop to 800psi before and it hesitated/shuddered until the pressure came back up.

Anything under about 1200 psi starts causing issues. The lowest I have seen mine go is 6 mpa / 900 PSI.

[StealBlueSho]

I have a hard time with their answer.. I have their most aggressive non-meth tune (4+x Race Tune) and the LOWEST I have ever seen my rail pressure drop was 1950psi...

Even Torrie doesn't like lower than 1500psi and he is a bit more liberal with variances in rail pressure than LMS...

Weird.... I'm glad they troubleshot it without charging you... the resultant answer is a bit baffling....

Are they still looking into it?

[polskifacet]

I have a hard time with their answer.. I have their most aggressive non-meth tune (4+x Race Tune) and the LOWEST I have ever seen my rail pressure drop was 1950psi...

Even Torrie doesn't like lower than 1500psi and he is a bit more liberal with variances in rail pressure than LMS...

Weird.... I'm glad they troubleshot it without charging you... the resultant answer is a bit baffling....

Are they still looking into it?

From what I understand they are looking into it as I am not the only one. Unfortunately Andy the shop manager was out last week which is probably the reason for the small amount of info I got. I am still chewing on all of this as I am still not sure what resulted from driving out there.

[polskifacet]

Recap:

• From time spent with AJP we know the issue is at a deeper level then just LMS tuning.
• Confirmed that both pumps are new/mechanically working correctly.
• Confirmed that car is making expected horsepower.

[lamrith]

I thought you said at lower rpms? I am confused... so I am guessing that a 0-60 pull is when you still have issues? Maybe I am misunderstanding?

0-60 or pretty much any time it downshifts @ WOT

Can you post a log of one of those WOT runs done after your last trip to LMS?  I am skimming the thread trying to catch up, but it would be nice to see a WOT run log of the current tune with all the current new parts and any tune changes they might have made.

As for Dyno, how did they dyno it?  Based on the smooth RPM curve it was the classic 3rd gear locked in pull.  They are not seeing WOT shifts (I do not think Dyno's can handle that sort of jerking), so not surprising they did a single gear pull, but it is something to keep in mind on why you are still having an issue.  Because of that sort of dyno tuning they will never see the issue you are having, as it is a nice flat/linear (while heavy) load pull they are doing.  A tuner cannot tune for something they cannot "see".  Dynos are great tuning devices, they just cannot simulate full range driving conditions.  I would have thought based on what you have been saying all along that they would have taken the car out someplace to really simulate your issue with WOT&shift performance.

I will probably deserve a Gibb's slap for this...  You have replaced all the pump side stuff already, but have you changed the fuel filter/blown the fuel lines clear during one of the times you have had to tear things apart?  Have you traced the hardlines and made sure one of the hardlines is not dinged, or kinked someplace?  How about soft lines?  Any sort is small deformation or restriction can cause it to have a hard time recovering from sudden spikes in demand. Might be "ok" on smooth RPM ramp up, just enough headroom to keep up, but not flow enough to recover from demands like can happen with WOT shifts as well as sustained demand staying WOT.

I am new to these cars myself, but think Steel might be on a good track.  You are talking with AJP, have you considered his boost regulator mod?  It takes the stress off the Fuel system post WOT shifts and keeps MAP constant and level the entire time without messing with the throttle blade.  Might be a bandaid to underlying problem, but I would be curious to see how your car did with that mod installed and tuned for it..?

[StealBlueSho]

Even on the third gear sweep he posted his fuel pressure is lacking.... I doubt the AJP mod will help much..