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Old Yesterday, 09:40 AM   #1
snidehockey
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Surging. Help please (logs attached)

So over the past 3 months I've gone from bone stock to:

Red coils
catless 3 inch downpipe
COBB Intake
COBB Accessport Stage 2 tune
stage 3 SBS drop in clutch disc

I've also had the intake manifold replaced by the dealer and the valve cleaning performed.

I noticed shortly after installing the COBB intake and tune that at different parts of the powerband the car seems to surge. RPMs don't spike or anything that seems like clutch slip, and it seems to happen most notably when cruising at about 75 or 80 in 5th or 6th at around 3000rpm.

It's not enough to raise or lower the mph but you feel yourself ever so slightly going faster slower faster slower and you can hear the hum of the motor higher and lower in sync with the feeling.

Like I said...MPH stay steady and RPM's don't waver even slightly. It just feels like maybe it's going in and out of boost or something? I dunno.

Anyway, I did some data logging when merging onto the highway last night and the last about 10 or 15 seconds of the log is where I felt this surging the most.

So any help would be huge!

https://datazap.me/u/snidehockey/sur...og=0&data=4-21
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Old Yesterday, 09:46 AM   #2
WalkerT
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Put a treadstone MAF straightener in the Cobb intake. There is turbulence across your maf not allowing your stft and your ltft to stabilize.
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Old Yesterday, 10:05 AM   #3
jay745
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Have you replaced the fuel filter?
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Old Yesterday, 03:07 PM   #4
thatspsychotic
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Quote:
Originally Posted by WalkerT View Post
Put a treadstone MAF straightener in the Cobb intake. There is turbulence across your maf not allowing your stft and your ltft to stabilize.
Could even be as simple as needing to clean your MAF as well. I used to get a degree of boost oscillation especially on boost onset, and cleaning my air filter and MAF sensor was enough to get rid of the issue. Different tunes are more or less sensitive to it.

It looks like the car is hunting for the correct boost/MAF target, and something MAF related like the flow straightener or cleaning the MAF should help.
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