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I have recently "re-chipped" with an APR 1 bar, and have been experiencing a potential problem...

When I get on it REALLY hard, then back off (such as you might when merging onto the highway- accelerate then check for space to merge into traffic), I get a very noticeable pulse in the transmission (or somewhere in the drivetrain between the wheels and the engine :roll: ). I happens VERY consistently when I back off the gas a bit, but not so much when I completely release (or perhaps I dont notice as much due to the deceleration or whatever).

I was chipped about a year ago on a Wetterauer 1.2 bar and have also driven several APR chipped cars and never felt this.

My diverter valve is a GFB (straight diverter- no blowoff or hybrid), and is about 2 years old. I also replaced all my vacuum lines about a year ago. Granted, I have not re-checked those, and will this weekend, but I dont think they are the cause (arent they usually responsible for loss of boost, not excessive power pulses?).

My thinking is this... isnt the wastegate responsible for removing excess boost when I get off the throttle? If it is failing, wouldnt that boost cause such a surge?

what can I do to troubleshoot this?

THX MUCHO!!!
 

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I am experiencing a similar problem.

APR chipped with a tt valve.

At full throtle car pulsates ... accelerating, decelerating.
Boost gauge shows 15 PSI peak boost and then drops to 10 or so.

I think the TT valve went bad. Could it be anything else?
 

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Try putting in a J-valve.... This fixed most (if not all of my surging problem). I am running the TT valve as well on my 00 1.8t. I know this also fixed live4spd's 04 1.8t with a Wett chip's surging problem too.

Ryan
 

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Discussion Starter #4
thx for the knowledge... i will start with that. Anybody got a good deal on a J-valve that you know of?
 

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The wastegate is pressure actuated and electronically controlled. If you were having surging under load it could be your wastegate since the pressure holds it open and a leaky diaphragm would cause problems. When you let off the throttle after running full boost the spring inside the wastegate diaphragm closes the wastegate. I suppose the spring could wear out but it's doubtful.

Some of the folks over on the Vortex have had luck with the J valves. Apparently the N75 valves are kind of finicky, certain ones work well with certain cars. If your problem was with the electronic part of the system I'd suspect it. Since the N75 can only control the wastegate when there is pressure I don't think that is the problem (no boost pressure when you are off the throttle).

My guess is that your GFB is clogged with oil and the piston may be sticking. First clean out the round thing on the top of your intake hose (remove the part of the cold air hose attached to the radiator support for better access). The "round thing" I'm talking about is connected to the PCV pipe (the 1" diameter black pipe running around behind the engine) and is supposed to keep the engine from sucking oil from the PCV system under boost. At elevated boost levels it tends to allow oil to get sucked through anyway. Then remove your GFB and clean it out. Probably just dipping it in some gasoline would work fine.

It sounds like RobsB is having detonation since his is happening under load. The N75 will reduce boost when the car senses knock, try using colder spark plugs (or install new ones), better fuel, or bigger injectors.
 
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