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Surging. Help please (logs attached)

S

snidehockey

Passed Driver's Ed
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/surging?log=0&data=4-21
 
WalkerT

WalkerT

Go Kart Champion
Put a treadstone MAF straightener in the Cobb intake. There is turbulence across your maf not allowing your stft and your ltft to stabilize.
 
thatspsychotic

thatspsychotic

Ready to race!
WalkerT said:
Put a treadstone MAF straightener in the Cobb intake. There is turbulence across your maf not allowing your stft and your ltft to stabilize.
Click to expand...

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.
 
Carlosfandang0

Carlosfandang0

Autocross Newbie
I used to get this occasionally and my car is stock.

Just thought though, when I first noticed this it felt almost as if the brakes were being applied very very slightly in short bursts (particularly on a bend) and it was decided that it was being caused by the fact that the front tyres were far far more worn than the rears and fitting new tyres stopped it, we think it was the ABS thinking the front wheels were spinning faster and intervening, be it via the XDS or a different system was never decided though, it may be worth logging what the brakes are doing when you feel it!


Sent from my iPhone using Tapatalk
 
Last edited:
S

snidehockey

Passed Driver's Ed
Thanks for the answers guys.

So far I cleaned the MAF with CRC MAF cleaner (put it in a bag etc.) and no change.

I'll look into the treadstone thing as well as fuel filter. As for the tires, they are fairly new Pirellis...I'd like to think that's not the case but that scenario is interesting and something I never considered.
 
Carlosfandang0

Carlosfandang0

Autocross Newbie
snidehockey said:
Thanks for the answers guys.

So far I cleaned the MAF with CRC MAF cleaner (put it in a bag etc.) and no change.

I'll look into the treadstone thing as well as fuel filter. As for the tires, they are fairly new Pirellis...I'd like to think that's not the case but that scenario is interesting and something I never considered.
Click to expand...



It’s likely not the case but may be worth checking with VCDS to see live what the brakes are doing at the moment you feel it happening, if only to eliminate the scenario!


Sent from my iPhone using Tapatalk
 
thatspsychotic

thatspsychotic

Ready to race!
snidehockey said:
Thanks for the answers guys.

So far I cleaned the MAF with CRC MAF cleaner (put it in a bag etc.) and no change.

I'll look into the treadstone thing as well as fuel filter. As for the tires, they are fairly new Pirellis...I'd like to think that's not the case but that scenario is interesting and something I never considered.
Click to expand...

Sticking with common issues, do you have any other driveability issues? Failed PCV valves can cause all sorts of strange problems, has your PCV ever been changed?
 
G

giotisjohn92

New member
Hey Snide,

I have the exact same issue that you are experiencing. All gears with the exception of first make the car surge right before it hits 3000 rpms if I am flooring it. If I accelerate gradually the problem seems to disappear. I have cleaned the MAF I have ran LiquiMolly valve cleaner and full system flush with an oil change. I have changed to one step colder spark plus and have the r8 coil pack. I have changed my pcv valve but still the problem persists. I will look at the diverter valve next to see if that hasn't failed in any way. I am stage 2 unitronic with full exhaust and cai. I will let you know if I find anything else. I hope we both figure this out.
 
M

MK6gti12

New member
I only get that slightly on cold start but I'm not sure if it's just the fact I have the HPA Intakeanifpld or the fact that the intake uses a 3" MAF. I didn't have any of that before I had the intake manifold put on in conjunction with replacing my CTS turbo intake with the Cobb intake.
 
S

snidehockey

Passed Driver's Ed
Hey quick update...

So I got the air straightener mentioned above and it seems to have resolved my issue.

I've been on the highway twice and haven't felt it at all.

Earlier I datalogged but haven't pulled them yet...when I do that will confirm it.
 
damagi123

damagi123

Go Kart Champion
giotisjohn92 said:
Hey Snide,

I have the exact same issue that you are experiencing. All gears with the exception of first make the car surge right before it hits 3000 rpms if I am flooring it. If I accelerate gradually the problem seems to disappear. I have cleaned the MAF I have ran LiquiMolly valve cleaner and full system flush with an oil change. I have changed to one step colder spark plus and have the r8 coil pack. I have changed my pcv valve but still the problem persists. I will look at the diverter valve next to see if that hasn't failed in any way. I am stage 2 unitronic with full exhaust and cai. I will let you know if I find anything else. I hope we both figure this out.
Click to expand...

snidehockey said:
Hey quick update...

So I got the air straightener mentioned above and it seems to have resolved my issue.

I've been on the highway twice and haven't felt it at all.

Earlier I datalogged but haven't pulled them yet...when I do that will confirm it.
Click to expand...



do either of you happen to have spacers on your O2 sensors
 
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