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Hi All

I have now fitted nice new NGK's to my 1987 9000 2.0t and my boost seems to be a bit irregular. I have turned the boost up using a blled valve, and it now entering the higher end of the red area on the in-dash boost gauge and drops back down to the start of the red. I am not getting any pinking or fuel cut.

Any ideas

Dan,
 

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Dan, it sounds like the APC is winding back the boost to me. This could be for several reasons- including that it's detecting knocking.

As it's a standard ECU, it isn't mapped to cope with higher boosts adequately and it may also be simply that it is turnig the boost down back in to a range it is mapped for.

Also, most mappings do allow for a temporay peak in boost to get you going quicker under acceleration. In doing so, the ECU has to predict the rate of rise from a known lookup table. By putting the bleed valve in, you could be making the pressure rise rate quicker and thus be getting more temporary overboost.
 
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