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Stutter at WOT


a.lim
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I'm trying to diagnose a problem here. My car stutters at WOT (wide open throttle) when it hits boost. I believe this "stutter" is different from the common stutter issue that some owners have during mid RPMs when accelerating. I even got a CEL one time when I was going WOT but it turned off quickly and my AccessPort didn't read any codes. Under boost and WOT it almost sounds like my turbo spool is fluctuating up and down very fast. It's hard to explain, but I took some data logs. I would greatly appreciate it if someone can take a look at it and shed some light. :)

 

Mods include:

-Blouch Dominator 2.5R turbo

-DW 750cc injectors

-Walbro 255 LPH

-Perrin FMIC

-AVO intake

-Tial BOV

-Cobb AP

datalog18.csv

datalog16.csv

Edited by a.lim
mods
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You have some knock from 4000-4400 RPM, it should be fixed but it's not terrible.

 

Can you do a LV and log knock sum? Also, check your misfire (roughness) counts and post up your mods.

 

Something is up. On datalog 18 your mass airflow is jumping all over the place on WOT and you made a lot less power (and less boost) than on datalog 16.

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Hmm, interesting that the CEL came on then went off. My friend had a similar problem with his STi and a shitty tune. The CEL was wastegate malfunction with stutter but only at wot once in a while, pretty sure it ended up being fuel cut....he's getting retuned saturday and will find out how it goes at EFI :)
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You have some knock from 4000-4400 RPM, it should be fixed but it's not terrible.

 

Can you do a LV and log knock sum? Also, check your misfire (roughness) counts and post up your mods.

 

Something is up. On datalog 18 your mass airflow is jumping all over the place on WOT and you made a lot less power (and less boost) than on datalog 16.

 

I'm going through my AP now. I enabled Roughness for cylinders 1-4 and knock sum, but I don't see "LV" what exactly does that stand for?

 

Are any of these variables it?

-Dynamic Advance

-Feedback Knock

-Fine Knock Learn

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Hmm, interesting that the CEL came on then went off. My friend had a similar problem with his STi and a shitty tune. The CEL was wastegate malfunction with stutter but only at wot once in a while, pretty sure it ended up being fuel cut....he's getting retuned saturday and will find out how it goes at EFI :)

 

I was searching over NASIOC about the stuttering at WOT and everyone was saying it might be electrical related. But I don't see how?

 

Was your friend's issue definitely a wastegate malfunction?

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I was searching over NASIOC about the stuttering at WOT and everyone was saying it might be electrical related. But I don't see how?

 

Was your friend's issue definitely a wastegate malfunction?

 

Wastegate malfunction is the code, it's caused by overboosting- much of which can be dealt with through a tune albeit all mechanical items are proper. I think his code went away on its own, not sure. You should do some logging and post it up....

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LV = Learning View, it's a completetly different reader and can be downloaded on the romraider forums, you will need a tactrix cable to do it tho. It basically shows your fuel correction trims and learned knock table...

 

Do a WOT run while logging

 

RPM

Load

Wastegate

MAf V

Maf g/sec

Feedback knock correction

Fine knock correction

Boost

Timing

Roughness on each cylinder

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LV = Learning View, it's a completetly different reader and can be downloaded on the romraider forums, you will need a tactrix cable to do it tho. It basically shows your fuel correction trims and learned knock table...

 

Do a WOT run while logging

 

RPM

Load

Wastegate

MAf V

Maf g/sec

Feedback knock correction

Fine knock correction

Boost

Timing

Roughness on each cylinder

 

I did a quick log this morning before I got to read this post. I added a couple more variables. I'm getting high numbers on cylinder 3 and I'm assuming that's not good. I'll do another log with the variables you mentioned, but here's my latest log for now.

datalog20.csv

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Looks like the misfires may be the cause of the problem. I suggest that you swap the injector to another cylinder and see if the misfire moves along with it. If there is no change, swap coillpacks and see iff the misfire moves. I get 0 misfires at WOT.

 

Also, you are knocking at 4000 rpm pretty consistantly it seems...gotta get that fixed.

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  • 2 weeks later...
....the common stutter issue that some owners have during mid RPMs when accelerating....

 

I have this problem. Can anyone point me to the thread where I can get some tips on resolving this issue? Or tell me what the problem is? I am still currently tuning my stage 2 tune. Thanks

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  • 7 years later...

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