Car Studdering at high boost between shifts

[SiNiST3R]

Well put it this way when i shift from 2nd to 3rd the boost hits 19psi and will studder just abit, i did a 3rd gear pull to tune it and it will pop about once on that run. I am very stumped on this any help would be alsome.

Things i did and checked.

AFPR set to 43PSI with the Vac line off.
New NGKs 7es gaped at .028
Boost at 19psi
Did boost leak test and fixed all Leaks


mods that count

SX AFPR
550 Injectors
Walbro 255lph
Evo3 B16g
Supra Side Mount IC
upper/lower piping/Greddy Type-s
turbo back exhaust
SAFC-II

Thanks if ya can come up with my answer me and my local buddies are stumped

 

[Thomas91169]

on a 3rd gear pull there is no studder, however, when going from 2nd to 3rd at full boost, when he hits 3rd and spools and hits full boost, it studders.

o2 is .94 across, timing curve is gradual slope till 16(91 octane).

-----------------edit:did not see his original post, kinda just retold the story

oh zane your last pull didnt pop(least i dont remember it)

 

[SiNiST3R]

Guess everyones stumped on this i know it could be many things, today i double checked the gap on the plugs(.028). Made sure am at 43-44PSI FP, not really sure why it does this just got done racing a Mustang GT pulled on him by way to much the power seems to be there, but i was watching the boost guage when it does studder it loses 1-2 pounds of boost each times. very weird. leak tested and no leaks.

 

[pneumo]

OK so it stutters when the turbo is re-spooling after a shift, right? Can you log it and see what the injector duty cycle is? It's possible the fuel settings are a little rich around 4-5k rpm. You're not venting your BOV are you?

 

[90blacktsiawd]

Have you tried checkin your spark plug wires? My valve seals are leaking and i know its time for new plugs/ maybe wires when my car studders at like5k and up. Just a thought and it would be cheep to test it out.

 

[SiNiST3R]

Nope not venting, i have not checked the plug wires thou they are NGKs 7.5MM i belive i bought them about 3 years ago.

 

[eclipsefwd]

My car did the exact same thing. I thought it was something serious but it ended up being very simple. It was just way too rich in between shifts. Try leaning it out around 4500 - 5000 rpm, or wherever your shift point is. .94 seems very rich, I am usually .88 - .90. That should to the trick.

 

[SiNiST3R]

come to think about it, that maybe the problem, i have 550s/and 255lph i think am just gonna retune what would you guys recomend for a starting high base with 550 -18% across the board sound good ad go from there?

 

[td06hkiko]

Well put it this way when i shift from 2nd to 3rd the boost hits 19psi and will studder just abit, i did a 3rd gear pull to tune it and it will pop about once on that run. I am very stumped on this any help would be alsome.

Things i did and checked.

AFPR set to 43PSI with the Vac line off.
New NGKs 7es gaped at .028
Boost at 19psi
Did boost leak test and fixed all Leaks


mods that count

SX AFPR
550 Injectors
Walbro 255lph
Evo3 B16g
Supra Side Mount IC
upper/lower piping/Greddy Type-s
turbo back exhaust
SAFC-II

Thanks if ya can come up with my answer me and my local buddies are stumped

My Car did the same thing for a long time. I even did a boostleak test and no leak. SO I went ahead and checked my SPARKPLUG GAP AND THEY WERE WAY OFF. I am now gapped at .28 and studdering was gone. Car runs perfect. YOu should Check your SParkplug gap and make sure that they are .28 IF you are gonna run more boost they should be closer more like .27 or so. Good luck and hope this fixes your problem.