boost seems to cut out

**oneighty** · 06-21-2008 05:30 PM

OK, I read through the majority of this thread and many others:
http://www.audizine.com/forum/showth...ht=sel+scaling
now I am running a 2000 ATW so I know a few things are different but the problem seems similiar. Basically after the engine warms up when i get into boost over 8psi it feels like the throttle opens and closes and opens and closes then finally opens and then pulls on through to redline. I am chipped, K&N drop in, Forge 004, N249 bypassed and have the 4.7v diode on the MAP sensor and a MBC in parallel with the N75 since I was getting the 'positive deviation code' so I turn down the boost and get 'negative deviation' but I cant seem to find a good median. Im new to VAG/Lemmi but not all new to tuning(DSM background), but I cant seem to smooth out the car. I couldnt quite tell from the above thread if Id be better off without the diode mod.

**oneighty** · 06-26-2008 06:52 AM

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**mike-2ptzero** · 06-26-2008 08:00 AM

I dont understand what your trying to acheive by running a MBC in parallel with the N75 and the diode mod. Only thing you gain with running the MBC/N75 combo that way is to decrease boost spikes, this is most likely causing you to throw the deviation codes when the turbo first spools up.

Are you trying to run more then 20psi? That is the only reason to use a 4.7 zener diode on the map sensor.

**oneighty** · 06-26-2008 09:35 AM

Im only trying to run around 17psi, when I first installed the chip the throttle was pretty jerky so after searching from what I understood I could smooth out the jerky throttle with the diode, then after i did that it would spike real fast so I got a MBC to stop the spike and put in a S4 N75 since I was thinking mine was shot. So I found that thread his symptoms seemed close but at the beginning of the thread I read that the diode is a bad idea unless you run a MBC alone, and then further on I read that its better to run it with the mbc in parallel. So really I just want to achieve 17psi on the stock turbo and Im not sure if the diode is really helping or hurting with the drivability.

**mike-2ptzero** · 06-26-2008 09:50 AM

The diode is hurting since it is meant to keep the ecu from seeing anything above 18psi. So using the diode for just 17psi is pretty useless.

You might want try taking the diode out and just running the MBC.