stuttering RPM, loss of power at high boost, logs inside

under load, when I get near 6000rpm, i can feel the engine stuttering and I can see the rpms no longer increasing smoothly. the car definitely does not pull has hard to redline (7300rpm)...sometimes the stuttering is more abrupt and I have to let off the gas almost instantly...this problem is more noticeable once the motor heats up, and it gets worse the hotter the motor is...it was really bad the last two weeks as we had record breaking temperature highs...

 

mods:

stock internals

rotated mount GT35R turbo

rotated intake manifold

perrin fmic with custom piping

turboxs type H BOV VTA

snow performance water meth kit

ID1000 injectors

romraiderlog_20110727_101828.csv

romraiderlog_20110727_101915.csv

romraiderlog_20110727_102005.csv

Nothing looks out of the ordinary on the log except your AFR - I assume you do not have a WB02 and that is the stock sensor reading?

 

Aslo spool is really slow - not sure if that is normal for that setup.

Pull a LearningView. Not an expert by any means, but I suspect you have learned knock.

no wb02, that is correct...

 

spool for that size of turbo is correct as far as I know...it is a conservative tune due to stock internals, but it is behaving poorly since the weather has gotten really hot...

Car seems to be leaning out badly past 4400rpm

the meth starts to spray at 7psi boost and 30 PWM...keep in mind it is not a wideband sensor reading, just stock.

yea..once you go WOT the stock o2 is pretty useless in the stock location.

 

Post up a LV - after closer review your timing is funky after 4000 RPM - it is bouncing around a lot. Could be learned knock that is pulling timing...without knowing what your target timing is, it is hard to tell. A LV will show any pulled timing up top.

attached 2 more logs and LV right after logs.

 

during second log, CEL came on...misfire cylinder 1 and 3, and wastegate solenoid A Low, P0245...

 

funny thing is, at partial throttle, the car pulls really hard and there is no stumble/studder sensation at all...when motor is still heating up, it pulls strong too...

 

I am not sure how to read learning view besides trouble codes...any help is appreciated...

romraiderlog_20110727_190341.csv

romraiderlog_20110727_190530.csv

A couple of things to look into. Your idle fuel trim is way off (ECU is richenning up the mixture by 15%), i would look for a vacuum leak somewhere. You cruising fuel trims are also not great, right now the ECU is leaning out the mixture by more than 4% - that is fine at cruise, but 4% leaner on the highend during WOT is not good. Again - this may be a result of a leak somewhere. You also have some learned knock that needs to be addressed, but it is not terrible.

 

Overall - the misfire on 1 and 3 is probably the cause of your studdering. I would swap injectors and see if the misfire code moves...then move on to swapping coil packs. A leakdown test is also a good idea...

 

The one good thing is you are not knocking on the WOT runs and your IAM is at 1.

 

good luck.

there is not much I can do about the tune but send this info to the tuner and see what he says...in terms of the leaning out, it could be because of the meth...at 7psi it starts to spray and increase to full spray at a higher boost level, and at 18psi it goes into power mode...I would need a wideband 02 to confirm if im running lean or not...

 

in terms of the misfire, the fact that it is only doing it once the motor heats up and only under high load, I don't think it is the injectors as I do not see them being affected by increased heat, I could be wrong...I am going to start with the plugs...they are one step colder and have been on the car for over a year, but have only seen 15000km...i have no rough idle issues that I can feel, and I don't experience the studdering at all unless im on it...my other guess is the gap on the plugs...i'll start there as the plugs are cheap...

I think you should check for a vacuum leak too - make sure all the lines are attached correctly.

i'll go over the vacuum lines again...I did it a few days ago and everything looked good...

so after a part throttle pull in fourth gear this past wednesday night, the studder problem has completely vanished...im guessing it was just a fouled up spark plugs that have cleaned off...still going to replace them tomorrow...

Also next time that you log include fine learning knock correction, feedback learning knock correction, and iam. Those parameters will tell you if the car is knocking during the pull and where.

^ Our ECU have the knock sum parameter (which lil_z_33 is logging); knock sum monitors the knock sensor and increments any time there is a knock event during the pull. So if knock sum increments anywhere on the log, you will know exactly when and where. It is a great parameter.

 

I like to check IAM right before a pull and for learned knock I do a LV right after the pull(s)...

So the problem is back. Funny how it came back when the humidity came back. When it went away, the engine light turned off and then came back on today when it got stupid humid. I havent checked what the code is yet. I changed the plugs today and went over all the vacuum lines and still its hesitating up top. Once i pull the code, if it is misfire on 1 and 3 again im gonna move the coil packs to the other side and see if the cel will reflect that. Other then that, i dont know. I dont think its the injectors as they only have like 7000km on them.

I would bet money you have a boost leak. Build a pressure tester and pump up your intake track to about 15 psi and all will become clear.

 

-Steve

so I have replaced all the intercooler piping, I had new stuff made up a few months back because I had used piping with shitty welding, plus I didn't like the fitment nor the placement of the BOV...all new couplings and t-clamps instead of worm gear clamps...while it was colder outside last week, the car pulled as hard as it is supposed too...

 

now the temperature has gone up significantly, and my misfire codes have come back, now on cylinders 1, 3 and 4, not just 1 and 3...i have gone over all boost tubes and vacuum lines and everything is tight, real tight....spool up is faster than ever, but as soon as I hit around 5000rpm, the car is sputtering and bucking, and what sounds like unburnt fuel igniting in the cat...the plugs were changed last month as well...I do not think it is the injectors as they are less than a year old (ID1000's), and I only get this issue at high boost in 3rd gear or higher...I am guessing it is the coil packs...furthermore, I do not have a turbo blanket on my gt35r, nor is my downpipe wrapped...engine runs extrememly hot when it is hot outside, I am not even sure if the rad fans come on anymore...