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turbo: sputtering under heavy throttle

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7.6K views 8 replies 5 participants last post by  apoji187  
A
#1 ·
Today I brought the car under heavy throttle for the first time in along time, because for quite some time there's been icy conditions. I noticed that now when I'm under heavy throttle, like 70% + There's sputtering.
Like a "Puh Puh Puh" about two every second - I'm assuming misfire...
This starts to happen at about 7-8lbs of boost. Of course I backed off when it started to sputter - I'm assuming detonation - due to the cold weather..

Under normal conditions, the engine is fine - I can lay on it for a second or two in passing, and break the tires loose, etc..seems to only happen at high boost levels and/or heavy throttle

EGT's are normal and not excessively high but moderate not exceeding 1200F.
Fuel pressure is stable at around 45-46psi..
no wideband in the car..

any educated opinions?
too rich, plugs fouled, time to install my MSD?
 
I
#2 ·
could be a rich condition from a boost leak, or you bov could be leaking at that boost level

tuning, of course, is a viable reason as well

what is done to the car in detail

-gte
 
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A
#3 ·
It's an original SRT stage 2 kit with the doo doo manifold
HKS SSQV on the pressure pipe, after the intercooler (I'll try tightening it up tommorrow)
Using the e-manage, which was tuned in warmer weather 440 cc injectors.
Walbro GSS340 255lph pump
3" exhaust
Greddy Profec-B, set external wastegate on low (all the way up)- set to sharp.
BOV is not teed..nor is boost controller.

I do have close to 20k miles boosted.

It could be that its just cold out - and I need some tuning.

It almost feels like a boost leak, but the pressure seems to stay constant and or rise. I'll bead some silicone sealant around my couplers tommorrow and see if that helps.
 
I
#4 ·
is the turbo slower to respond (it should be quicker because of the cold weather)

it could be many things (even an exhaust leak)

do you have any CEL's ?

you can pressurize the intake system, to see if you have leaks, tuning is a good idea as well

a simple way to add more fuel across the board, to compensate for the denser (is that a word?) air coming in, is to raise base fuel pressure a couple of pounds. if it gets worse, or does not improve, and bucks at many different rpm points, it may not be tuning

-gte
 
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#6 ·
No CEL's
Turbo is real quick to respond, it hits hard quickly
However, I did weld a bung onto my down pipe this weekend for the egt probe. there might be a pinhole leak..but i dont think that would be it.

Ill pressurize the system this weekend and see whats up..ill post the results..i've been racking my brain for weak spots..and i've thought of one or two.
i got a new set of plugs on the way, so we'll see what happens.

Thanks for the tips gte.
 
S
#8 ·
Your plugs are comin man!
I put the new ones in. As soon as I can get em mailed I'll get em mailed.
 
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